The Ragweed and Melon Allergy Connection

Allergy & Asthma Network

The Ragweed and Melon Allergy Connection

Do you ever get an itchy mouth when eating watermelon or cantaloupe? What about that luscious peach that left your gums raw and irritated?

Could be you’re one of millions whose pollen allergy also sets them up to react to certain foods.

It’s called oral allergy syndrome (OAS) and what’s behind it are protein similarities among some pollen-producing trees, grasses and weeds and related fruits and vegetables. For instance, a person who gets a runny nose or drippy eyes when exposed to ragweed pollen in the air might develop an itchy, tingling mouth or lips when eating banana, melon or cucumber.

As many as one every three people with seasonal allergies may experience oral allergy syndrome. The exact number is unclear because the condition often goes undiagnosed. Symptoms can be mild and go away quickly, making it less ly that people will see a doctor for diagnosis. Or parents might not associate a child’s dis of a vegetable with an allergic reaction.

Common Food Triggers

Oral Allergy Syndrome is particularly common among people allergic to ragweed – some 36 million people in the U.S. – but it also affects people with other allergies. Researchers have identified specific foods that relate to birch, grasses and ragweed.

Birch pollen: almond, apple, carrot, celery, cherry, hazelnut, kiwi, peach, pear, plum, potato, pumpkin seed

Grass pollen: kiwi, melon, peach, tomato

Ragweed pollen: banana, chamomile, cucumber, echinacea, melon (watermelon, cantaloupe, honeydew), sunflower seed, zucchini

Oral Allergy Symptoms

Symptoms of OAS include itchiness, irritation, and/or mild swelling or hives in or around the mouth.

Symptoms can also seem quite random. For instance, many people are only bothered during pollen season; the rest of the year they can eat pollen-related foods with no problem. So if you’re allergic to ragweed, a melon in February (when ragweed is dormant) may not bother you at all, while one in September (when ragweed pollen counts are high) could set off symptoms with the first bite.

Some people with OAS will react to fresh foods but not cooked or canned varieties. If you have grass allergy, for instance, you may be able to eat tomato sauce on pizza but develop itchy mouth from fresh tomato in a salad. Others may find they can eat certain varieties of a fruit (Macintosh apples versus Granny Smith, for instance) or fruits without their skins.

Oral Allergy Diagnosis and Treatment

While most oral allergy symptoms will go away when you stop eating the food, it’s a good idea to see an allergist for an individual consultation any time you experience allergy symptoms related to food.

 Food-related symptoms can sometimes alert you to a more dangerous allergy, such as latex.

A board-certified allergist can give you an accurate diagnosis, advise you which foods to avoid and recommend treatments to relieve symptoms.


Oral Allergy Syndrome: Why Eating Honeydew (or Celery and Carrots too!) Can Make Your Throat Itch

The Ragweed and Melon Allergy Connection

You’re happily digging into a crisp fruit cup. Ah, refreshing honeydew and cantaloupe! But just a minute later, it hits you. Your throat is itchy, kinda tingling. What gives?

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

No, you’re not imagining it. Allergist Martin Smith, MD, says the phenomenon you’re experiencing is called oral allergy syndrome, or food-pollen syndrome.

“It’s actually the most common type of food allergy in adults,” Dr. Smith says. “It’s a mild form of contact allergy to fresh fruits and vegetables in people who have hay fever.

“You’ll feel an itching, tingling, sometimes a mild fullness or swelling in your tongue, lips or back of your throat pretty soon after you start eating.”

Those with hay fever (also called allergic rhinitis) may be affected by several types of pollen — including ragweed, birch and grass. Possibly 50 to 75 percent of them may also be affected by food-pollen syndrome from spring through mid-September.

The offending triggers

Birch pollen (March & April): Pitted fruits (apple, peach, plum, pears), carrots, celery, almonds, hazelnuts.

Grass pollen (May to early July): Tomatoes, potatoes, melons, oranges.

Ragweed pollen (mid-August to mid-September): Melons (cantaloupe, honeydew, watermelon), zucchini, banana.

Why it happens

Symptoms occur almost immediately after eating the offending food, usually in the cross-reacting pollen season. That means, Dr. Smith says, you will usually have less symptoms if you eat imported melon in January.

“The reason you get the sensation is because the protein in the uncooked fruit or vegetable is very similar to the pollen protein that’s found in birch, ragweed and timothy or orchid grasses,” he explains. “Your body kind of confuses the fruit protein to be the actual pollen from the birch tree, ragweed or grass.”

This causes irritation or swelling in the mouth that’s usually pretty mild. Any annoyance or discomfort disappears pretty quickly, Dr. Smith says, because your stomach acid rapidly destroys the offending protein once swallowed.

Usually, most pollen-food suffers can tolerate eating a small quantity of the fruits or other foods. If the symptoms are bearable and mild, there’s no harm in continuing to eat the food. But in some folks, the reaction is quite bothersome, and they usually can’t eat that food when the offending pollen is in season.

How serious is it? And what to do …

It’s important to point out that you can only get oral allergy syndrome if you’re allergic to pollen, Dr. Smith notes.

“You can only get it from food that comes from plants,” he says. “So you can’t get it from seafood, dairy, eggs or meat. And you usually only get it from the fresh, uncooked version of fruits and vegetables because the proteins in the foods that cause this syndrome are easily destroyed or changed when you heat the food.”

Most times, no treatment is needed. But Dr. Smith says there are two types of people who should see an allergist.

First, those who have a reaction to nuts almonds or hazelnuts. “You don’t want to confuse a mild food-pollen allergy with a more serious food allergy — which could be more severe the next time,” he says.

And second, anyone who has systemic symptoms (this happens in less than 5 percent of food-pollen allergy suffers) hives, vomiting, difficulty breathing, reactions that are getting progressively worse or if you experience symptoms when eating cooked versions of the foods.

“Otherwise, just avoid the raw fruits and vegetables in the relevant pollen season,” Dr. Smith advises. “So skip that watermelon in the middle of August.”

If you find avoiding your favorite foods tough in all three pollen seasons, you can talk to your allergist about allergy shots, he notes, which often help people tolerate the foods better.

Don’t want to bother? There’s two more options. You can peel the food to see if that helps you tolerate it better, though you might then experience tingling in your hands from contact with the skins, often seen with potatoes. Or, you can heat it up.

“Just put the fruit in the microwave for 10 seconds,” Dr. Smith says. “It doesn’t sound very appetizing, but it works a lot of the time.”

So nuke that next fruit cup? Your choice.


The Ragweed and Melon Allergy Connection

Oral allergy syndrome can be seen in patients with pollen allergy who experience mouth and throat itching, typically when eating fresh fruit and vegetables such as apples, melons, celery and carrots, but also with peanuts and tree nuts such as hazelnut.

Oral allergy syndrome symptoms

  • Most symptoms are felt in the mouth with itching
  • Gastrointestinal symptoms
    • Nausea
    • Vomiting
    • Diarrhea
    • Abdominal pain
  • Symptoms pollen exposure
    • Itchy eyes and nose
    • Congestion
    • Runny nose.
  • Rarely patients develop throat swelling, hives or anaphylaxis

Most often oral allergy syndrome begins with a pollen allergy such as birch, ragweed or grass. Oral symptoms are seen among 70% of birch sensitive patients and 20% of grass sensitive patients.

An allergy to particular foods may follow.

  • Birch — Hazelnut, carrot, kiwi, parsley, almond, soybean, celery, potato, orange, peanut, apple family (i.e. peaches, plums, nectarines)
  • Ragweed — Milk, melons, banana, lettuce, mint, cucumber, zucchini, chamomile tea, egg, white potato
  • Grasses — Legumes (peas, beans, soybeans, all beans such as kidney, navy, garbanzo, etc.), grains, apple, carrot, celery, orange, tomato, white potato, zucchini
  • Cedar — Apple, cherry, bell peppers, kiwi, paprika, tomato
  • Sage, Mugwort — Celery, coriander, potato, tomato, carrot, fennel, peppers, sunflower, parsley, broccoli, cabbage, cauliflower, garlic, onion, caraway
  • Marigold — Milk
  • Cedar, juniper — Beef, yeast
  • Elm — Milk, mint
  • Oak — Egg, chestnut, apple
  • Pecan, hickory — Corn, banana, apple
  • Pigweed, amaranth— Pork, black pepper
  • Ivy Ciliata (poison ivy)— Wheat, pork, black pepper
  • Mesquite — Cane sugar, orange
  • Cottonwood — Lettuce
  • Dust — Peanut, snails, oysters, clams, scallops
  • Latex —  Banana, avocado, kiwi, chestnut, potato, cinnamon, plantain, tomato, walnut
  • Candida— Cheeses, mushrooms, vinegar, fermented moldy foods

Oral allergy symptoms are seen more often during peak allergy season:

  • Spring for birch
  • Summer for grass
  • Fall for ragweed

What causes oral allergy syndrome?

Compounds in certain foods are similar to compounds on the surface of pollen grains. Acting as a local allergen, these compounds can trigger itching in the mouth and throat among sensitized people. Many of these compounds are concentrated near the skin of fruits, so a peeled apple may cause fewer symptoms than the unpeeled fruit.

Many food allergens degrade with cooking and digestion so apple sauce may cause fewer symptoms than fresh apples; carrots in a soup may cause fewer symptoms than raw carrots. People on stomach acid blocking medications may experience more gastrointestinal symptoms, as these medications impair gastric digestion.

Treatment can include:

  • Limit the amount and frequency of foods that cause symptoms, particularly during peak allergy seasons.
  • Treat the underlying pollen and food allergy with sublingual immunotherapy.
  • Use oral antihistamines as needed to control temporary symptoms.
  • Contact us to discuss treatment


Watermelon allergy: Symptoms, diagnosis, and what to avoid

The Ragweed and Melon Allergy Connection

In March 2020, the Food and Drug Administration (FDA) released a safety alert to warn the public that epinephrine auto-injectors (EpiPen, EpiPen Jr., and generic forms) may malfunction.

This could prevent a person from receiving potentially life saving treatment during an emergency.

If a person has a prescription for an epinephrine auto-injector, they can view the recommendations from the manufacturer here and talk with their healthcare provider about safe usage.

A watermelon allergy is rare. However, if a person reacts to watermelon, there may be additional foods to avoid.

If a person with an allergy does not eat watermelon often, they may not know what has caused their symptoms. It could be an allergy to a different food, or an unrelated illness.

The symptoms of a watermelon allergy are similar to those of other food allergies. A doctor can perform tests to identify the problematic food.

A watermelon allergy usually develops during childhood, but some people develop it as adults.

Share on PinterestA person with a watermelon allergy may experience hives or stomach pain.

Watermelon allergies share symptoms with other food allergies. Symptoms usually occur within a few minutes of contact with the melon.

Some of the most common watermelon allergy symptoms include:

  • persistent coughing
  • hives
  • an itchy tongue or throat
  • stomach cramps
  • stomach pain
  • nausea or vomiting

A severe allergic reaction can trigger anaphylaxis, which can be life-threatening.

Anyone experiencing a severe reaction to watermelon should receive immediate medical attention. They may require an injection from an epinephrine auto-injector, such as an EpiPen, before help arrives.

Symptoms of anaphylaxis include:

  • trouble breathing
  • trouble swallowing
  • shortness of breath
  • swelling of the throat, face, or tongue
  • nausea
  • abdominal pain
  • vomiting
  • wheezing
  • shock (from low blood pressure)
  • vertigo (a feeling of dizziness)

Anyone experiencing a watermelon allergy for the first time should talk to a doctor. The doctor can confirm the diagnosis and provide suggestions about treating and preventing future reactions.

A skin prick test is the most common way to diagnose a watermelon allergy.

The test involves pricking the skin and placing a small sample of watermelon on the area. If a person is allergic, a raised bump is ly to appear on the skin after a few minutes.

Results of a blood test can also indicate an allergy. However, it can take a few days or weeks to receive them.

However, some people may test positive for an allergy but experience no symptoms from the food, according to the American College of Allergy, Asthma, and Immunology.

A doctor may request a challenge test, which requires a person to eat a small amount of the food in a clinical setting to see if a reaction occurs.

Share on PinterestAn epinephrine pen can treat a severe allergic reaction.

An individual can usually treat a mild allergic reaction with over-the-counter medication.

If a person knows that they have a severe allergy to watermelon, they should carry an epinephrine auto-injector, in case of accidental exposure.

Anyone who witnesses someone experiencing anaphylaxis should:

  • call emergency medical services
  • assist in using an epinephrine auto-injector
  • help the person remain calm
  • remove restricting clothes, particularly those around the throat
  • lay the person flat with their feet elevated
  • if the person starts to vomit, turn their head without raising it
  • if needed, administer CPR

Do not offer food or drink to a person experiencing anaphylaxis.

If a person has a severe allergic reaction, they should talk to a doctor right away about prescribing an epinephrine auto-injector.

A person should see a doctor after their first allergic reaction, particularly if the reaction was severe.

The doctor will take a medical history and discuss symptoms. They may be able to diagnose an allergy, which will be especially helpful for people who are unsure of the cause of their symptoms.

If necessary, the doctor may refer a person to an allergist. They can test for various triggers, prescribe an epinephrine auto-injector, and offer advice.

Young children are more ly to develop watermelon allergies than adults.

A doctor will need to diagnose the allergy in a child, and the treatments are similar for children and adults.

Though uncommon, it is possible for babies to be allergic to watermelon. Follow a pediatrician’s advice, and introduce new foods gradually. This can make identifying allergies easier.

Anyone allergic to watermelon should avoid similar foods and vegetables, such as:

  • honeydew melons
  • cucumbers
  • cantaloupes

A person may also want to avoid foods that cause similar reactions in the body, including:

  • kiwis
  • celery
  • peaches
  • bananas
  • oranges
  • avocados
  • zucchini
  • tomatoes
  • papayas

Ragweed pollen can also trigger reactions during the summer months.

Before ordering a restaurant in a meal, inform the server about any food allergies.

Watermelon allergies are uncommon, but they can trigger reactions ranging from mild to severe. The allergy is most common in children.

Most people can control or prevent allergic reactions by taking over-the-counter medications and avoiding triggers.

A doctor can help a person with a severe allergy to prepare for accidental exposure.


Oral Allergy Syndrome

The Ragweed and Melon Allergy Connection

Note: this form is NOT sent over an encrypted connection. Do NOT send HIPAA protected information using this form. If your matter is urgent, please call our offices at 407-380-8700

It’s time to do something about your allergies

Call 407-380-8700 for an appointment or information

One little girl with severe ragweed allergy used to complain to her father that eating melon, banana, cucumber and tomato made her throat and inner ears itch. He thought it was just her imagination.

However, it is now recognized that symptoms such as these are caused by a type of food-related allergic reaction called Oral Allergy Syndrome (OAS).

Adults and children who are allergic to inhaled pollens (tree, grass and ragweed pollens) and who usually have seasonal allergic rhinitis (hay fever) may experience symptoms after eating certain raw vegetables, nuts, seeds, or fresh fruit.

Food and Pollen Cross-Reactions

OAS is caused by nearly identical allergens that are present in both fresh food and pollens, called cross-reacting allergens. The foods that are most commonly associated with OAS are listed in the accompanying table. The symptoms of OAS occur where the food touches the mouth, which results in itching or swelling of the lips, tongue, back of the throat, or roof of the mouth.

Because the allergens that are responsible for these symptoms are usually destroyed by heat from cooking procedures, affected individuals can usually eat fruits or vegetables that have been cooked, baked, or canned. For example, a person may experience itching of the tongue and roof of the mouth when eating a fresh apple, but have no problems after consuming apple pie or apple sauce.

Specific cross-reactions have been identified between ragweed pollen and watermelon, other melons, and members of the gourd family including cucumber and squash. Cross-reactions between birch pollen and celery, kiwi, apples, and hazelnuts have also been found. See the accompanying table for other fresh fruit and vegetable allergen cross-reactivities with grass, tree and ragweed pollens.

Diagnosis and Treatment

Allergists can make the diagnosis of OAS most often from a complete clinical history.

If skin testing with commercial extracts of the incriminated fruits and vegetables or blood testing for food-specific IgE (allergic) antibodies produces negative results, skin tests done with fresh fruits or raw vegetables will usually be positive. Skin testing to the cross-reacting pollens will also be positive.

The natural history of patients with OAS has not been well studied. Some researchers report that both allergic rhinitis (hay fever) symptoms and OAS symptoms go away if the affected individual receives immunotherapy injections with extracts of the cross-reacting pollens. Patients with OAS also report that some improvement occurs with the use of regular doses of antihistamines.

However, this form of treatment is not advised in patients with any history of systemic (affecting the entire body) reactions to foods. In patients who experience not only oral symptoms but serious systemic reactions to foods, identifying the responsible food and strictly avoiding that food is the key to successful long-term management.

While Oral Allergy Syndrome is not a typical food allergy, it is a food-related allergic reaction. It may improve with treatment of the allergic rhinitis, but patients with persistent bothersome symptoms should avoid raw forms of the offending foods, especially during the pollen season.

VEGETABLES: carrots, celery, parsley, potatoes, tomatoes

SEEDS & NUTS: fennel seed, hazelnut (filbert), sunflower seeds

FRUITS: apples, apricots, bananas, cantaloupes, cherries, honeydew melon

Back to top | Back to patient education | Contact us


Foods to avoid for pollen allergies

The Ragweed and Melon Allergy Connection

When certain fresh fruits, raw vegetables, seeds or nuts are consumed, typically during spring and early fall when inhalant allergies are more common hay fever, the body's immune system recognizes and essentially mistakes a plant protein in the food for pollen, and this irritant triggers what allergy specialists call a cross-reaction.

For people who experience what's called “oral allergy syndrome” (OAS; also referred to as “food-pollen allergy syndrome” and “fruit-pollen syndrome”), the following symptoms may occur after eating the offending food:

  • itchy or swollen lips
  • tingling at the back of the throat
  • scratchiness on the roof of the mouth
  • watery or itchy eyes

“[OAS] may affect up to 5 percent of the population, and is clearly more prevalent among those with seasonal pollen allergies, specifically those who have an allergic sensitivity to tree, weed and/or grass pollen,” Clifford Bassett, MD, founder and medical director of Allergy & Asthma Care of New York, and assistant clinical professor of medicine at NYU School of Medicine, told Reader's Digest.

Although symptoms can be serious, most reactions of OAS are minor and occur in the mouth or throat.

Which foods should I avoid?

If you're allergic to grass pollens, avoid fresh figs, as they may cause a pollen- allergic reaction. (Photo: vesna cvorovic/Shutterstock)

It depends what tree or weed allergy you have. For those allergic to grass pollens, you’ll want to avoid:

  • oranges
  • tomatoes
  • melons
  • figs

As noted above, foods that cause a pollen- allergic reaction are usually fresh or raw. If you love oranges but notice they cause a reaction, orange juice, although it's not as nutritiously-dense as an orange, might not cause the reaction. Same thing with tomatoes: Freshly picked ones from the vine might cause an itchy throat, but tomato paste might not trigger a negative reaction.

If you're allergic to weed pollens, specifically ragweed, the following foods may trigger OAS:

  • banana
  • cantaloupe
  • cucumber
  • melons
  • zucchini
  • artichoke
  • teas of Echinacea, chamomile and hibiscus

Some other foods that trigger OAS in more than one type of allergy include:

  • apples
  • almonds
  • celery
  • strawberry
  • cherries

If you eat something that triggers allergies, you'll notice symptoms almost immediately. Most allergists would agree that OAS symptoms appear no more than half an hour after eating.

“Patients will typically decide on their own, without any discussion with a doctor, whether they enjoy the apple enough to put up with an itchy mouth, or whether they hate the itchy mouth enough to avoid the apple,” Dr. Robert Wood, chief of pediatric allergy and immunology at Johns Hopkins Children's Center, told CNN.

What else can I do to avoid OAS?

During allergy season, cut down on cross reactions by eating more cooked vegetables instead of raw. (Photo: DronG/Shutterstock)

Eliminate or greatly reduce artificial additives, artificial sweeteners and pesticides, as they could potentially cause bronchial spasms and histamine reactions of the eyes, ears, nose, throat and skin.

Also, boost your immune system. The weaker your immunity, the more ly your body will experience a cross reaction. Drink plenty of water, exercise daily, get at least 7 hours of sleep a night and supplement with anti-oxidants (under the care of a doctor or nutritionist).

If you use anti-allergy medicine, try to choose natural anti-inflammatory and natural anti-histamine nutritional supplements.

During allergy seasons, consume more cooked vegetables and try to eliminate the offending raw fruits. Use a food journal to determine which foods are triggering allergic reactions.

Editor's note: This article has been updated since it was originally published in May 2011.


Does Eating Melon Make Your Mouth Itch?

The Ragweed and Melon Allergy Connection

Kaleidoskop / Picture Press / Getty Images

Most people are familiar with hay fever and food allergies, but many do not realize there can be a connection. Oral allergy syndrome, also known as a pollen-food syndrome, can cause people who suffer from hay fever to experience symptoms such as an itchy mouth or scratchy throat when eating certain fruits, vegetables, or tree nuts.

Oral allergy syndrome is caused by allergens that occur in both pollen and certain foods which can cross-react, triggering the immune system to mount an allergic response. People with oral allergy syndrome usually only experience a reaction when eating raw fruits or vegetables as cooking alters the proteins involved.

People with a history of allergic reactions to birch, ragweed, or grass pollens can develop oral allergy syndrome, but the condition usually doesn't develop in young children. Rather, older children, teens, and young adults may suddenly develop oral allergies even though they have been comfortably eating the same foods for years.

Certain foods correlate with particular environmental allergens. For example, if you find you are allergic to various types of melons, you also probably experience allergic rhinitis caused by ragweed pollen.

If you are affected by oral allergy syndrome when you eat fresh fruit melon, you may experience itching, burning, or stinging sensations of the mouth, throat, and tongue as your body reacts to the proteins in the fruit.

The symptoms generally last only a few seconds or minutes, as the proteins that cause the symptoms are broken down quickly by saliva.

Other common correlations include:

  • Birch pollen: apple, almond, carrot, celery, cherry, hazelnut, kiwi, peach, pear, plum
  • Grass pollen: celery, melons, oranges, peaches, tomato
  • Ragweed pollen: banana, cucumber, melons, sunflower seeds, zucchini

Because the symptoms usually fade quickly, treatment usually is not necessary or helpful. People with ragweed allergy may also notice symptoms of OAS with eating fresh bananas and cucumbers.

A careful history can usually provide enough clues to your doctor that oral allergy syndrome may be present. Sometimes, skin prick tests and oral food challenges can aid in diagnosis. Diagnosis of oral allergy syndrome is reached after taking a patient’s clinical history and, in some cases, conducting skin prick tests and oral food challenges with raw fruit or vegetables.

While anaphylaxis, a serious allergic reaction that compromises breathing, is not very common, it can occur with oral allergy syndrome. Therefore, it is important to obtain a proper diagnosis and find out whether carrying an epinephrine auto-injector is warranted.

Thanks for your feedback!

What are your concerns?

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. American College of Allergy, Asthma & Immunology. Oral Allergy Syndrome. Updated March 21, 2019.


It Might Be Your Allergies

The Ragweed and Melon Allergy Connection

Each fall, as ragweed releases its pollen into the air, people with seasonal allergies start sniffling and wheezing. But the problems don't always stop there.

“For some people who are allergic to ragweed, if they eat a banana, their mouth starts to itch or their throat can feel its swelling,” says Mary C. Tobin, MD, an allergist at Rush.

The reason? These people have pollen food allergy syndrome, also known as oral allergy syndrome. This means they experience allergic reactions to certain fruits and vegetables that contain proteins similar to those in allergenic trees and weeds.

For example, people who have birch pollen allergies might react negatively to carrots, celery, apples and peaches, while those allergic to ragweed may need to avoid melons and tomatoes in addition to bananas.

People often consume these foods in combination with others, of course, and the reactions they trigger can vary widely and mimic the symptoms of other conditions. As a result, it's not always easy to identify the condition and link the culprit foods with the symptoms they cause. But doing so, Tobin says, can lead to effective treatment.

Identifying symptoms

Un common allergies to foods such as peanuts and tree nuts — which most often appear in early childhood — pollen food allergy syndrome typically develops in adolescence or adulthood, after repeated exposure to the cross-reacting pollens.

Tobin estimates that the condition, which can appear suddenly, afflicts about 50 percent of adults with seasonal allergies and accounts for about 60 percent of all allergic reactions to food in adulthood.

But many people with the condition might not realize they have it because these reactions aren't limited to the hives and itchy mouth commonly associated with allergies. Reactions can also include neurological problems, such as migraines or trouble concentrating, and array of gastrointestinal issues.

“We have a lot of people who come in with nonspecific abdominal pain, diarrhea, cramps or incapacitating gastrointestinal problems,” Tobin says. “And we've found that in many of these people it's allergies that hadn't been recognized as part of their allergy symptoms.”

Finding treatments

To determine which allergies are causing which symptoms in each patient, Tobin and several colleagues — including a gastroenterologist, a pathologist and a dietitian — track and experiment with patients' diets in addition to conducting any necessary tests.

This process can be complicated because patients often have reactions to more than one food. Someone who gets hives from bananas, for example, might get cramps after eating cantaloupe.

The good news for these patients is that simply treating their seasonal allergies can in many cases solve gastrointestinal issues and other problems they might not have known were related.

“If the foods causing the problems are cross-reacting with pollen, you can avoid those foods, take antihistamines, and a lot of the time, you get better,” Tobin says. “For someone who has been suffering from these problems that hadn't been explained, that can be life-changing.”

Pollen food allergy syndrome may cause people with allergies to the following pollens to react to the related foods:

  • Birch tree: apple, carrot, celery, cherry, fennel, kiwi, parsley, peach, pear, plum
  • Grass: celery, melon, orange, peach, tomato
  • Ragweed: banana, cucumber, melon, zucchini


Food Allergies and Cross-Reactivity

The Ragweed and Melon Allergy Connection

A food allergy occurs when the immune system overreacts to a food. The most common type is when the immune system makes a type of antibody called IgE to proteins in a particular food. This is an IgE-mediated food allergy. When exposure to the food occurs, symptoms start quickly.

Symptoms include any or several of the following:  skin itching, hives, swelling of the skin, nausea, vomiting, diarrhea, breathing difficulty (wheezing, repeated throat clearing, cough, throat tightness), or anaphylaxis.

Anaphylaxis is a severe allergic reaction that is rapid in onset and progressive. Symptoms of anaphylaxis involve more than one organ system from the above list.

They can also include dizziness or loss of consciousness (from a drop in blood pressure) and other serious, potentially life-threatening complications. Anaphylaxis can occur with any IgE-mediated food allergy.

The most common food allergens are milk, egg, wheat, soy, peanut, tree nuts, fish and shellfish.

Cross-reactivity occurs when the proteins in one substance are the proteins in another. As a result, the immune system sees them as the same.  In the case of food allergies, cross-reactivity can occur between one food and another. Cross-reactivity can also happen between pollen and foods or latex and foods.

Because of cross-reactivity, testing and diagnosis of food allergies can be challenging.

Since the immune system sees the similar proteins as the same, a positive skin test or blood test (serum IgE) can result for a food, yet the patient may be actually allergic to a substance that is cross-reactive to that food.

However, the individual may or may not have any allergic symptoms from eating that food.  The individual may not have allergic symptoms from a food that is cross-reactive with another food or pollen to which the individual is allergic.

This is true even though they have a positive skin test or blood test to that food.  This point cannot be emphasized enough. Many people end up avoiding foods because of a positive test and in some cases, they may have been eating that food before without any problems.

Cross-Reactivity Between Cow's Milk and Milk from Other Mammals

There is a high degree of cross-reactivity between cow's milk and the milk from other mammals such as goat and sheep. In studies, the risk of allergy (resulting in symptoms) to goat's milk or sheep's milk in a person with cow's milk allergy is about 90%.

The risk is much lower, about 5%, for allergy to mare's milk (or donkey's milk) which is less cross-reactive with cow's milk.

Cross-Reactivity Between Foods in the Same Animal Group

Cross-reactivity is uncommon between foods in the same animal group. For example, most people with an allergy to cow's milk can eat beef and most people with an allergy to egg can eat chicken without any symptoms to the respective meats.

Cross-Reactivity Between Peanut and Other Legumes (Soy and Beans)

Peanuts and soybean are in the legume family, which includes beans and lentils. A common question that comes up for people with an allergy to peanut is whether they can eat soy-based foods or other beans.

More than 50% of peanut-allergic individuals will have a positive skin test or blood allergy test to another legume (soy, other beans) but it turns out that 95% of them can tolerate and eat the cross-reactive legumes.

Many years ago, it was common to recommend avoidance of legumes, including soy, because of a peanut allergy but this practice has been proven unnecessary.

Cross-Reactivity Between Peanut and Tree Nuts or Seeds

As noted above, peanuts are legumes and are not related to tree nuts (almonds, walnuts, cashews, etc.). However, about 35% of peanut-allergic toddlers in the U.S. have or will develop a tree nut allergy. It is fairly common to be “co-allergic” to tree nuts if a child is peanut allergic.

Doctors thus recommend that young children avoid tree nuts if they are peanut-allergic. Safety is also a concern. Young children may have a hard time distinguishing a tree nut from a peanut. Thus, there is the potential of cross-contamination of tree nut products with peanut.

Studies have investigated whether the common occurrence of allergy to both peanut and tree nuts is due to allergen cross-reactivity. At least one study revealed that there MAY be some cross-reactive parts of the allergic proteins in common. But true cross-reactivity is unknown.

However, the larger issue is that allergy to tree nuts is common in peanut allergic individuals. Doctors should watch for tree nut allergy in peanut-allergic individuals. Their recommendations should be made on an individual basis.

The same hold for peanut allergy and allergy to seeds such as sesame seed. There are a few individuals who are allergic to both.

This is ly due to the occurrence of more than one food allergy in highly allergic individuals rather than cross-reactivity.

With respect to tree nuts, there is high degree of cross-reactivity between cashew and pistachio and between walnut and pecan. Most people who are allergic to one tree nut are not allergic to all tree nuts.

Cross-Reactivity Between Fish

There is a lot of cross-reactivity among different species of fish including fresh and salt water fish. The risk of allergy to other fish when an individual is allergic to one fish is about 50%.

Cross-Reactivity Between Shellfish

Shellfish, fish, peanuts, and tree nuts are commonly associated with severe, potentially life-threatening reactions. There is a high degree of cross-reactivity among the crustacean shellfish (shrimp, lobster, crab, crawfish). The risk of allergy to another crustacean shellfish is 75%.

The risk may be lower for cross-reactivity between crustacean shellfish and non-crustacean shellfish (mollusks) such as clam, oyster, scallop, mussels. Of note, there is cross-reactivity between chitins (a component of exoskeleton of shellfish and insects) in dust mites and crustacean shellfish.

This can result in “false positive” testing for shellfish without any clinical symptoms.

Cross-Reactivity Between Pollen and Foods (Pollen-Food Syndrome or Oral Allergy Syndrome)

Some individuals with pollen allergies (allergic rhinitis or hay fever) can develop symptoms around and in the mouth and throat immediately after eating raw fresh fruits, vegetables, nuts or seeds that contain proteins cross-reactive to the pollens. This is known as oral allergy syndrome or pollen-food syndrome.

For example, people with birch pollen allergy may experience symptoms after eating raw apples, peaches, pitted fruits, carrot, peanut and hazelnut among others. wise, ragweed allergic individuals experience symptoms with melons among other foods. Symptoms can include itching or tingling of the lips, tongue, and roof of the mouth or throat.

In addition, there may be hives around the mouth area where the food came into contact with the skin or swelling of the lips, tongue, and throat tightness. In less than 3%, symptoms may become systemic (beyond the mouth or throat) or result in anaphylaxis.

Cooked forms of the foods are usually tolerated because the food proteins which are pollen cross-reactive are fragile and are broken down when subjected to heat or stomach acids (so, for example, raw apples can cause symptoms but an apple pie can be eaten without any symptoms). Not all people with pollen allergies have oral allergy syndrome (OAS), but many do.

And, for those who do have oral allergy syndrome, they may experience symptoms with some but not all foods cross-reactive to a particular pollen to which they are allergic.

Cross-Reactivity Between Latex and Foods

Latex is a natural product that is derived from the milky substance extracted from a rubber tree. Common natural rubber latex products include latex gloves and balloons. Latex can cause several types of allergic or non-allergic (irritant) reactions.

The most concerning type is an IgE-mediated allergic reaction to latex that results in immediate reactions such hives, swelling, wheezing, and anaphylaxis. About 30 to 50% of people with IgE-mediated allergies to latex can experience symptoms with any or several fruits cross-reactive to latex including most commonly banana, avocado, kiwi, and chestnut.

However, the overall prevalence of IgE-mediated reactions to latex is rare. Most reported reactions are due to contact sensitivity.

A Final Word

Individual reactions vary when it comes to food allergies and cross-reactivity. And, because of the additional challenges in diagnostic testing posed by allergen cross-reactivity, it is important to talk with your allergist-immunologist (allergist) about your symptoms with foods.

For example, people with birch or grass pollen allergy may have a positive skin test to peanut as well.

Your allergist has expertise in the area of allergen cross-reactivity and can help in making an accurate diagnosis and providing guidance as to whether a cross-reactive food needs to be eliminated or not.

Dr. Vaishali Mankad is in private practice at Allergy Partners of Raleigh, a hub of Allergy Partners, PA which is the nation's largest single-specialty practice in Allergy, Asthma, and Immunology. She specializes in the care of children and adults with food allergies and other allergic conditions, asthma, eczema and immunologic conditions. Dr.

Mankad hails from the windy city of Chicago. She moved to Durham, North Carolina in 1998 where she completed a three-year pediatrics residency at Duke University Medical Center.   She stayed at Duke for her fellowship training in Allergy-Immunology from 2003 until 2005 and subsequently served on the faculty in the division of Pediatric Allergy and Immunology at Duke until 2007.

She then continued her career in private practice. Dr. Mankad lives with her husband and two children in Chapel Hill, North Carolina.

No experience has taught her more about the day to day and long term challenges faced by individuals and families dealing with food allergies than her own daughter who has IgE-mediated food allergies to egg, peanut, tree nuts, white potato and food-protein enterocolitis to cow's milk.

Medical review July 2015.