Medical Encyclopaedia › Urticaria (short definition)
In brief: In hives (urticaria), itchy wheals form on the skin that look like they do after contact with stinging nettles. In some people, deeper swellings, for example on the lips or eyelids, occur as well (angioedema). Urticaria is usually harmless and subsides quickly; if it lasts longer than six weeks, it is called chronic urticaria.
How does urticaria develop?
The trigger is mast cells in the skin, which release messenger substances such as histamine. These dilate the small blood vessels and make them more permeable: fluid leaks into the tissue, and red, raised wheals form that itch severely. A single wheal typically disappears without trace within 24 hours, while new ones can appear elsewhere. If the swelling extends into deeper layers of the skin, angioedema develops, which tends to feel tight or painful rather than itchy.
Forms and triggers
- Acute urticaria: lasts no longer than six weeks and is the most common form. An infection is often behind it, less often medicines such as painkillers from the NSAID group or a food allergy. The trigger often remains unknown.
- Chronic spontaneous urticaria: wheals occur for more than six weeks without any recognisable external stimulus. In many of those affected, autoimmune processes play a role; allergies are only rarely the cause here. The disease can last months to years but often resolves by itself.
- Chronic inducible urticaria: wheals are caused by certain physical stimuli, such as rubbing or scratching (dermographism), cold, pressure, heat, light or sweating during exertion.
Diagnosis
The diagnosis is usually based on the typical appearance and the history; photos of flare-ups help if the wheals have disappeared by the time of the doctor’s appointment. In acute urticaria, extensive investigation is usually not necessary. For chronic courses, the guideline initially recommends a few basic tests such as a blood count and inflammatory markers, with further tests depending on the findings. Inducible forms can be demonstrated with provocation tests, for example with an ice cube if cold urticaria is suspected. A diary of symptoms and possible triggers is often helpful.
Treatment
Known triggers should be avoided where possible. The first-choice medicines are modern, non-drowsy antihistamines (second-generation H1 antihistamines). If the usual dose is not enough, it can be increased up to fourfold after consulting a doctor. If the effect is still inadequate, the antibody omalizumab, injected under the skin, may be considered in chronic spontaneous urticaria; in severe cases also ciclosporin or newer approved active substances. Corticosteroids are only used briefly for severe flare-ups, not as long-term therapy. The aim is complete freedom from symptoms, which can be achieved in most of those affected.
When to call the emergency number immediately?
If shortness of breath, difficulty swallowing, hoarseness, swelling of the tongue or throat, dizziness, circulatory problems or vomiting occur in addition to wheals, anaphylaxis may be present. This is an emergency: call the emergency services immediately (112 in Europe) and, if available, use the adrenaline auto-injector. Recurrent swellings without wheals and without response to antihistamines should be assessed by a specialist, because rare forms such as hereditary angioedema are treated differently.
Related terms in the encyclopaedia
Wheal, Angioedema, Mast cells, Histamine, Dermographism, Cold urticaria, Omalizumab, Anaphylaxis, Itching
Sources
- Zuberbier T et al.: The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy 2022
- AWMF-S3-Leitlinie Urtikaria (Deutsche Dermatologische Gesellschaft, DDG, und Deutsche Gesellschaft für Allergologie und klinische Immunologie, DGAKI)
- Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen (IQWiG): gesundheitsinformation.de – Nesselsucht (Urtikaria)
- Europäische Arzneimittel-Agentur (EMA): EPAR zu Omalizumab (Xolair)
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor, dentist or pharmacist. Last updated: October 2026.