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Drug allergies are immune-mediated hypersensitivity reactions to medications that can range from mild skin reactions to life-threatening anaphylaxis. These reactions occur when the immune system mistakenly identifies a medication as harmful and mounts an inappropriate inflammatory response. Early recognition and management are crucial to prevent serious complications and guide future medication choices.
Drug allergies typically involve IgE-mediated Type I hypersensitivity reactions, where initial drug exposure leads to sensitization and antibody production. Upon re-exposure, cross-linking of drug-specific IgE antibodies on mast cells and basophils triggers degranulation and release of inflammatory mediators like histamine and leukotrienes. Non-IgE mediated reactions can also occur through direct drug-induced complement activation or T-cell mediated delayed hypersensitivity responses.
Clinical evaluation focuses on distinguishing true drug allergies from adverse drug reactions or intolerances through detailed history-taking and physical examination. The timing of symptom onset relative to drug administration, previous exposure history, and characteristic allergic symptoms like urticaria, angioedema, or anaphylaxis help confirm the diagnosis. Management involves immediate discontinuation of the offending agent, supportive care with antihistamines or corticosteroids, and documentation to prevent future exposures.