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Anaphylaxis induced by subcutaneous allergen immunotherapy

David I Bernstein, MD
Section Editor
John M Kelso, MD
Deputy Editor
Anna M Feldweg, MD


Subcutaneous allergen immunotherapy (SCIT) is an essential therapy in the clinical practice of allergy. However, it can induce anaphylaxis on rare occasions. This topic reviews the frequency, risk factors, and appropriate strategies for management and prevention of anaphylaxis due to SCIT, as well as the clinical features of fatal and near-fatal allergic reactions, and systemic reactions (SRs) to allergen injections.

The indications for SCIT, the treatment of anaphylaxis, and fatal anaphylaxis due to many different causes are discussed separately. SRs to sublingual immunotherapy (SLIT) are also reviewed separately. (See "Subcutaneous immunotherapy for allergic disease: Indications and efficacy" and "Anaphylaxis: Emergency treatment" and "Fatal anaphylaxis" and "Sublingual immunotherapy for allergic rhinoconjunctivitis and asthma", section on 'Specific studies and efficacy data'.)


Subcutaneous immunotherapy (SCIT) was introduced in the early 1900s. As early as 1916, systemic reactions (SRs) were reported to occur with 3.5 percent of subcutaneous grass pollen injections [1]. In 1986, the Committee on the Safety of Medicines in the United Kingdom reported 26 SCIT-related anaphylactic deaths over a 10-year period [2]. This report led to adoption of a mandatory two-hour postinjection waiting period in the United Kingdom. This was difficult to implement and essentially eliminated the use of this therapy for years until a one-hour standard observation period was accepted. A 30-minute postinjection observation period is recommended in the United States [3].


Systemic allergic reactions to SCIT — Systemic reactions (SRs) to subcutaneous allergen immunotherapy (SCIT) range from cutaneous manifestations (pruritus, urticaria, or angioedema at locations other than the site of the injection) to anaphylaxis. The World Allergy Organization has issued a new grading system for classifying clinical severity of SRs to SCIT (table 1). The risk of experiencing SRs may vary according to types of allergens, potency of the injected allergens, modes of allergen preparation and modification, and dosing protocols (eg, cluster or rush regimens are associated with higher frequencies of SRs than slow build-up regimens) [4].

As examples:

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Literature review current through: Nov 2017. | This topic last updated: Apr 15, 2016.
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