SELECTED ARTICLES FROM THE RECENT LITERATURE 2003

11/19/03

Pollen allergy causes G-I symptoms

Summary
It is well known that allergy to certain foods is more common in individuals with respiratory reactions to antigenically related pollens. In most instances, the reactions to the ingested foods are local "oral allergy syndrome" (OAS) manifestations. However, sometimes, more extensive G-I symptoms occur. The question remains whether such G-I symptoms can be induced by inhalation of the pollen itself.

To investigate this question, Magnusson et al of the Univ. of Gotenborg in Sweden investigated 9 subjects with birch pollen allergy who previously manifested OAS and/or G-I reactions to the foods which often cross-react with birch pollen. The patients were then observed carefully during the birch pollen season while avoiding all suspect foods. In 6 of the 9 patients there were OAS symptoms and 7 reported G-I symptoms such as abdominal pain, flatulence, diarrhea/constipation. In 4 of the 7 individuals such symptoms occurred only during the birch pollen season. In 5 of these patients, the G-I picture fulfilled criteria for a diagnosis of irritable bowel syndrome. No such G-I symptoms were observed during the birch pollen season in a non-allergic control group.

Reference
J Allergy Clin Immunol 2003;112:45-51

Editor's Comments
These findings suggesting that pollen exposure in allergic individuals can induce G-I as well as respiratory symptoms are very interesting and potentially quite important if confirmed by other groups. The mechanisms underlying the G-I symptoms observed here are not defined. One would first postulate a G-I reaction to pollen which was swallowed after inhalational exposure. However, the authors quoted findings that birch pollen allergens are 90% inactivated in the upper G-I tract and therefore unlikely to induce an allergic reaction by direct contact with the G-I mucosa. They postulate a possible G-I tract involvement in a systemic reaction to pollen allergens absorbed from the respiratory mucosa. Their biopsy studies did show eosinophil inflammation in the duodenum during the pollen season. More investigation is warranted.


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