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Pollen season aggravated intestinal inflammation in patients with birch pollen allergy

Birch pollen allergic patients experienced ongoing inflammation in their intestinal mucosa that was heightened during pollen season, according to recent study results.

Researchers recruited 32 patients, aged 18 to 50 years, with birch pollen allergy and 16 healthy nonallergic controls from the asthma and allergy clinic at Sahlgrenska University Hospital, Gothenburg, Sweden. The birch pollen cohort included 20 patients with gastrointestinal symptoms. Allergy investigation, including a questionnaire, and gastroscopy with duodenal biopsy were conducted, with blood samples and biopsies retrieved from May to June (pollen season) and November to March (off-season). Immunostaining for mast cells (IgE and tryptase), eosinophils, T cells (CD3) and dendritic cells (CD11c) was conducted in the biopsies. Pollen-specific IgE antibodies were determined.

Ten of the patients with gastrointestinal symptoms reported manifestations only during pollen season, while the others reported year-round symptoms. Worsening symptoms when ingesting birch pollen-related food was reported by one patient. Abdominal distension (73%), gases (72%), stomach pain (44%), diarrhea (44%) and constipation (33%) were reported most frequently.

“Patients in both pollen allergic groups showed a similar degree of intestinal allergic inflammation during the pollen season, regardless of gastrointestinal symptoms,” the researchers wrote.

There was an increase of eosinophils, mast cells and dendritic cells. During pollen season, significantly elevated levels of IgE antibodies to birch (rBet v 1), hazelnut (rCor a 1) and apple (rMal d 1) were experienced by patients with gastrointestinal symptoms.

“We show here that regardless of subjective gastrointestinal symptoms, patients allergic to birch pollen have clear signs of an ongoing allergic inflammation in their intestinal mucosa, which is aggravated during the pollen season,” the researchers concluded. “Furthermore, patients who experience GI symptoms show somewhat elevated levels to PR-10 proteins compared to asymptomatic patients, which could be associated with the intake of birch pollen-related food items.”

Disclosure: The researchers report no relevant financial disclosures.