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How to Spot and Treat Oral Allergy Syndrome

You may already know that you’re allergic to ragweed or that certain types of tree pollen make you wheezy. But did you know that certain foods can trigger the same kinds of allergic reactions? Oral Allergy Syndrome is caused by cross-reacting allergens that are found in both the pollen and certain raw fruits, vegetables, grains, beans, spices, seeds, and tree nuts.

Have you wondered why eating celery causes your tongue to feel strange? Does munching on hazelnuts or walnuts cause your throat to tighten? If you have a tree pollen allergy, you may be suffering from Oral Allergy Syndrome! The same may be true for people allergic to ragweed, Mugwort, and other weeds and grasses, who have a sensitivity to certain foods. Understanding the pollen/food connection can solve the mystery of adult-onset food allergies and save you from a lot of dietary grief.


What is Oral Allergy Syndrome?

The immune system, in the course of targeting viruses, bacteria, and other undesirable germs, will focus on specific proteins. Oral Allergy Syndrome is a reaction that occurs because the proteins in certain foods are very similar to those in specific types of pollen. If an allergic person’s immune system encounters this food protein, it confuses it for the pollen protein and causes a similar allergic reaction or makes existing symptoms worse. When this cross-reactivity happens with pollen and certain food items, it’s referred to as Oral Allergy Syndrome (OAS) or Pollen Fruit Syndrome (PFS). However, it isn’t just fruit that can be the cause. Pollen-Food Allergy is a more accurate name, and it’s quite common among adults. In fact, 50 to 75% of adults who have a birch tree allergy have an allergic reaction to apples or celery. More than 60% of food allergies are, in fact, cross-reactions between food items and inhaled allergens. OAS is also related to allergic rhinitis (hay fever).


What are the Symptoms of Oral Allergy Syndrome?

Symptoms can vary and typically occur within minutes after you eat a trigger food, although it may on occasion happen more than an hour later. Most commonly, the reaction is a burning or itching sensation in the mouth, lips, and/or pharynx. Other allergic reactions can include a skin rash or allergy symptoms in the eyes and nose. There may be swelling of the tongue, lips, and uvula as well as a feeling of tightness in the throat and hoarseness. While OAS is usually considered a mild food allergy, in more severe cases with highly allergic individuals, anaphylaxis may result. This can be extremely serious and may lead to difficulty in breathing or swallowing. With strong reactions, swallowing the food can cause a later reaction in the person’s gastrointestinal tract, such as indigestion, diarrhea, cramps, or vomiting. Any of these symptoms should be treated as an emergency. According to the American College of Allergy, Asthma & Immunology, researchers found that nearly 9 percent of patients had oral allergy symptoms that progressed to systemic symptoms with 1.7 percent of these cases leading to anaphylactic shock.


What Allergens Correspond to Which Foods?

Fortunately, there is some good news regarding OAS! The correspondences between certain types of allergens and food allergies is well known. If know you’re allergic to birch pollen and ragweed, for example, you’ll know which foods are potentially problematic.


Pollen Fruit Vegetables, Spices Nuts Grains, Beans, Seeds
Birch Apple, pear, plum, apricot, cherry, peach, nectarine, prune, kiwi, banana, avocado, fig, strawberry, dried plum, mango Potato, avocado, carrot, celery, green pepper, tomato, chicory, cilantro, fennel, parsley, dill, cumin, parsnip Hazelnut, almond, walnut, peanut, Brazil nut Soybeans, wheat, lentils, peas, beans
Ragweed Banana, melons (cantaloupe, honeydew, watermelon) White potato, pepper, zucchini, squash, cucumber, artichoke, hibiscus, paprika, dandelion, chamomile tea   Sunflower seeds
Mugwort* Mango Bell pepper, broccoli, carrot, celery, cauliflower, chard, garlic, onion, aniseed, caraway, coriander, dill, fennel, black pepper, parsley, cumin   Sunflower seeds
Weeds Melon, watermelon, fig, orange, kiwi Tomato    
Grasses (i.e. Timothy and orchard grass) Fig, melon, kiwi, watermelon, orange, peach Tomato, potato, celery, zucchini Peanut  
Alder Apple, cherry, peach, pear, strawberry, raspberry Celery, parsley Hazelnut, almond, walnut  
Wormwood Apple, melon, watermelon Carrot, celery, parsley, pepper, cilantro, fennel   Sunflower
Parietaria Cherry, melon      

Pollen and food association sources: 1. PubMed Central, Table 1: J Allergy (Cairo). 2015; 2015: 543928. Published online 2015 Nov 8. doi: 10.1155/2015/543928, 2. Adult Food Allergies – Harvard Health, 3. Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI, 4. Oral Allergy Syndrome | Symptoms & Treatment | ACAAI Public Website, 5. Oral Allergy Syndrome – The Need of a Multidisciplinary Approach, 6. Oral Allergy Syndrome (, 7. Oral Allergy Syndrome – Asthma and Allergy Affiliates.

*Mugwort is also associated with honey, which is a tricky subject when it comes to foods that contain allergens. Honey allergies are very rare but not unheard of and they can be serious. However, reports indicate that wildflower honey, made from wildflower nectar, has been used by allergy sufferers as a type of immunization, building up antibodies to pollen and other allergens. Honey has also been shown to have anti-histamine and anti-inflammatory properties, though further studies are needed.

Does OAS Only Occur During Tree, Weed, or Grass Pollination?

Sadly, no. While you’re at greater risk of having a food allergy when its corresponding allergen is in its pollination season, the symptoms can occur year round. However, having an idea of when to expect your allergies to peak can put you on guard to watch out for certain foods.

Depending upon where you live, tree pollen can make its appearance as early as February and last through May. Grass pollen can emerge in May in certain parts of the U.S. June is also a busy time for grass pollen, though it typically begins to subside by July. Fungus and mold have their heyday in the summer, to the great dismay of allergy sufferers who enjoy the outdoors—but that’s another topic! Late summer into early fall is ragweed time, which is a very popular allergen and the most common of autumn allergies. In warmer parts of the country, this can persist into October or November.


Do I Have Oral Allergy Syndrome?

You may suspect you have OAS if you suddenly develop an allergy to a food that corresponds to a known allergen. A few testing methods can confirm this. A clinical diagnosis may be as simple as a patient history that demonstrates a clear link between a food allergy and an allergic reaction. Or your doctor may suggest an elimination diet to stop eating foods you think may be problematic. You will then reintroduce them one at a time and watch closely for symptoms. You can also have a skin test in a lab, such as a scratch test, prick test, or blood test. A grid on your arm or back is marked off and extracts of various pollens and foods are applied to each section. Marks that develop indicate the amount of reaction. Blood tests may also be able to indicate OAS.


Is There Any Treatment for Oral Allergy Syndrome?

OAS can come and go over the course of your lifetime. And while there is no permanent cure for OAS-triggered food allergies, there are various treatments that can alleviate OAS symptoms as well as some preventative measures.

  • Avoid certain foods – This is the easiest and surest method. However, if you’re allergic to various foods, it may take time to discover which ones are the culprits. It may also be difficult to know the ingredients of every food item if you go to a restaurant or a family gathering.
  • Cook foods to destroy proteins that cause OAS – Depending on the food, you may be able to cook it to destroy the allergens. This will work with apples, pears, potatoes, tomatoes, and most soft fruits. However, with nuts and spices, heat won’t destroy all the allergens. Allergens in celery and strawberries are also heat resistant. Pasteurized fruit juices have been heat treated, so they are likely fine, but beware of smoothies, since they may contain unpasteurized juice.
  • Peel fruit – The skins of fruit often contain a lot of the problematic proteins. Wear gloves when peeling fruit you are allergic to. This will help avoid getting a skin reaction like hives.  
  • Rinse mouth with water and rest – If you have a reaction, this should be the first treatment. Hot drinks may also destroy certain proteins, thereby deactivating them.
  • Take an antihistamine – This may or may not work, since an OAS reaction will usually begin to subside after approximately 30 minutes. However, an over-the-counter antihistamine can prevent symptoms from lingering. Take it quickly once the reaction has occurred.
  • Manage your hay fever – If you know you have seasonal allergies, take antihistamines and a steroid nasal spray regularly throughout the allergy season to help cope with OAS symptoms. Be sure to start about 2 weeks before your allergy season begins.
  • Get immunotherapy or allergy shots – In more severe cases, and particularly if it is only one allergen, the immune system can be made less sensitive to that allergen. Immune therapy (with under-the-skin treatment) may be a treatment option.


Explore Your Food Allergies with Your Doctor

Since food allergy symptoms, in rare cases, can be severe, it is highly recommended that you consult your doctor or allergy specialist if you find yourself having allergic reactions to certain foods. They can help determine the best course of action for diagnosis and treatment.
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