Ragweed season and Oral Allergy Syndrome (OAS)

The pollens released by ragweed in late summer and early fall are the most common cause of autumn allergies. Depending on where you live, ragweed-driven autumn allergies can start in August or September and continue through October to November.

The ragweed family constitutes common soft-stemmed weeds that grow in much of the United States and Europe; it is a non-native species that is highly invasive and has harmful impacts on a range of sectors, especially human health[1].

A single ragweed plant can produce up to 1 billion pollen grains, which are broadly spread on windy days due to their lightweight and inclination for airborne flight. Wet and windy allergy seasons can result in a wider spread of ragweed pollen; this has a direct impact on the severity of allergy symptoms.

Symptoms and how to control them

Most ragweed symptoms are well known to individuals who suffer from seasonal allergic rhinitis (hay fever): sneezing; stuffy or runny nose; itchy eyes, nose and throat; and aggravated inhalation or asthma-related conditions. Ragweed pollen can also create skin irritations associated with allergic contact dermatitis and eczema.

Ragweed and Oral Allergy Syndrome (OAS)

Individuals with ragweed allergies and hay fever symptoms may experience irritation of the mouth, lips or throat when eating specific raw fruits, vegetables or foods including melons, milk, honey, zucchini and bananas. Allergists refer to this phenomenon as Oral Allergy Syndrome (OAS) and it occurs because the proteins found in those foods are very similar to those found in the ragweed pollen. The immune system of a symptomatic individual produces antibodies that are directed against the proteins of pollen and these antibodies also recognize the structurally similar proteins in food[2]. These food proteins can confuse the immune system and cause an allergic reaction, or worsen already existing symptoms. This phenomena is referred as cross-reactivity[3].

OAS is generally considered to be a mild form of food allergy. Unlike other food allergies, the OAS reaction is generally limited to the oral mucosa, lips, tongue and throat. Interestingly, cooked versions of cross-reactant foods may not elicit similar levels of reactivity since the proteins responsible for OAS might be impacted by the high temperature. Finally, although it would be rare for a patient would develop severe symptoms beyond the typical reactivity, OAS should be taken seriously since it can be an initial manifestation of a more serious food allergy. Individuals should see an allergist if such symptoms are noted. For this reason, it is essential that impacted individuals know the difference between OAS and typical food allergies as well as the treatments required for each condition.

If you have symptoms of OAS, you might want to avoid eating the following raw foods, especially during allergy season:

  • Banana

  • Cantaloupe

  • Honey

  • Watermelon

  • Cucumber

  • White potato

  • Zucchini


[1] Smith M, Cecchi L, Skjøth CA, Karrer G, Šikoparija B. Common ragweed: a threat to environmental health in Europe. Environ Int. 2013 Nov;61:115-26. doi: 10.1016/j.envint.2013.08.005. Epub 2013 Oct 17. PMID: 24140540. [2] Kashyap RR, Kashyap RS. Oral Allergy Syndrome: An Update for Stomatologists. J Allergy (Cairo). 2015;2015:543928. doi:10.1155/2015/543928 [3] American Academy of Allergy Asthma & Immunology: https://www.aaaai.org/conditions-and-treatments/library/allergy-library/outdoor-food-allergies-relate

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