Biphasic reactions to allergen immunotherapy ‘uncommon’
MedWire News: Results from an Israeli study suggest that biphasic systemic reactions to allergen immunotherapy are uncommon and tend to be mild in nature.
“An anaphylactic reaction is one of the alarming adverse effects of allergen immunotherapy,” explain Ronit Confino-Cohen (Meir Medical Center, Kfar-Saba) and Arnon Goldberg (Tel-Aviv University).
They add: “An anaphylactic reaction can be classified as either uniphasic or biphasic. In a uniphasic reaction, symptoms usually begin within 5 to 30 minutes after exposure to the allergen and disappear gradually. In biphasic systemic reactions, symptoms of the initial episode disappear and then re-emerge, usually within several hours after they have completely subsided.”
To investigate the incidence, characteristics, and outcomes of immunotherapy-associated biphasic reactions, the researchers studied data on 453 patients who received immunotherapy at Meir Hospital Allergy Clinic.
All the patients underwent peak expiratory flow (PEF) measurements before administration of immunotherapy injections. If an anaphylactic reaction occurred after an injection, the patient was asked to complete a 3-day symptom diary and undergo further PEF measurements. A biphasic reaction was defined as a late decrease in PEF of more than 20%, with or without accompanying symptoms.
The researchers found that just 131 anaphylactic reactions occurred after a total of 21,022 immunotherapy injections.
Most uniphasic reactions and all biphasic reactions occurred in patients who were being treated for allergic rhinitis. Biphasic reactions were also more common in patients with a low baseline PEF and those with asthma.
All biphasic reactions, which included nasal congestion, cough, itchy eyes, shortness of breath and chest tightness, were mild and subsided either spontaneously or after antihistamine treatment.
Confino-Cohen and Goldberg conclude in the Annals of Allergy, Asthma and Immunology: “Immunotherapy-induced biphasic reactions are uncommon. They tend to be mild and might be more common in patients with a low baseline PEF or concomitant asthma.”
They add: “Therefore, a short observation period should suffice for most patients. An extended observation period should be reserved for those patients with concurrent serious medical problems, according to the physician's clinical judgment.”
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By Mark Cowen