{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T09:04:00Z","timestamp":1774947840483,"version":"3.50.1"},"reference-count":38,"publisher":"IMR Press","issue":"3","license":[{"start":{"date-parts":[[2026,3,25]],"date-time":"2026-03-25T00:00:00Z","timestamp":1774396800000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Br. J. Hosp. Med. (Lond)"],"abstract":"<jats:p>The term \u201callergy\u201d is often used ambiguously, frequently applied to a broad spectrum of immune and non-immune reactions, which can create confusion in clinical practice. Whilst there is some controversy, the term \u201callergy\u201d is now primarily reserved for describing immunoglobulin E (IgE)-mediated (Type I) hypersensitivity. Accurate diagnosis requires distinguishing Type I reactions from their mimics, especially given the clinical overlap with non-IgE-mediated conditions. This review focuses on Type I hypersensitivity, detailing its immunopathogenesis, clinical features, and diagnostic strategies, with particular emphasis on the role of serum tryptase in confirming mast cell activation. A comprehensive clinical history is crucial to distinguishing IgE-mediated allergy from its mimics, focusing on timing, symptom reproducibility, and the identification of potential triggers. Cofactors like non-steroidal anti-inflammatory drugs, alcohol, and exercise may exacerbate reactions, complicating diagnosis. Prompt intramuscular adrenaline administration is essential in cases of anaphylaxis, while patient education and specialist referral are key to long-term management. The review also examines conditions that may mimic Type I reactions, such as chronic spontaneous urticaria or isolated angioedema. In addition to classical allergy, clinicians must consider conditions such as hereditary angioedema, neuroendocrine tumours, and drug-induced pseudoallergic reactions. Recognising these mimics is vital to prevent misdiagnosis, ensuring patient safety, and avoiding unnecessary allergy labels or suboptimal management. This article provides a structured framework for evaluating suspected allergy, enhancing diagnostic accuracy, and guiding appropriate, patient-centred care across allergy and related clinical disciplines.<\/jats:p>","DOI":"10.31083\/bjhm52244","type":"journal-article","created":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T08:00:46Z","timestamp":1774944046000},"source":"Crossref","is-referenced-by-count":0,"title":["If It Is Not Immunoglobulin E-Mediated Allergy, What Is It?"],"prefix":"10.31083","volume":"87","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9324-4474","authenticated-orcid":true,"given":"Sarah Louise","family":"Johnston","sequence":"first","affiliation":[{"name":"Department of Immunology and Immunogenetics, North Bristol NHS Trust, BS10 5NB Bristol, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3358-3578","authenticated-orcid":true,"given":"Ricardo","family":"Madrigal-Burgaleta","sequence":"additional","affiliation":[{"name":"Allergy & Severe Asthma Service, St Bartholomew\u2019s Hospital, Barts Health NHS Trust, EC1A 7BE London, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"16242","published-online":{"date-parts":[[2026,3,25]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","unstructured":"Kay AB. 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