Safety and low incidence of anaphylaxis in performing oral drug and food challenges in mastocytosis.

Background: Patients with mastocytosis (MC) have an increased risk of severe anaphylaxis. They report hypersensitivity reactions to drugs and food, but causality often remains questionable. Most allergy centers avoid oral challenge tests (OCT) in MC patients.

Objective: To determine the safety of food and drug OCT in patients with MC.

Methods: To retrospectively evaluate the safety and outcome of challenges to drugs and food including food additives, out of 126 adult MC inpatients, 83 patients had a suspicion of food or drug hypersensitivity and 445 OCTs were performed. History, clinical data and allergy test results highlighting OCTs were analyzed.

Results: Only 10 of 445 OCTs (2.2%) in 9 patients resulted in anaphylaxis. Drugs elicited reactions in 4/170 (2.4 %) patients: two patients to acetylsalicylic acid (2/39 tested patients, 5.1%), one to tramadol (1/12, 8.3%) and one to flurbiprofen (1/1). Anaphylaxis to food was recorded in 6/275 OCTs (2.2%); two out of 48 (4.1%) to α-gal, two to other foods and two to sulfites. Flushing or diarrhea occurred to histamine in 5/48 (10.4%), but also in 5/50 (10.0%) placebo challenges strongly questioning its relevance. Patients with proven anaphylaxis had more bone marrow MC and higher basal serum tryptase (71.3 vs. 44.3ug/l; p<0.05).

Conclusions: Challenge-confirmed food and drug anaphylaxis was rare in MC patients. Results have to be interpreted cautiously as placebo reactions did occur. Severe anaphylaxis was seldom, but may occur and should be met by emergency preparedness.