Urticaria is a skin condition characterised by erythematous, blanching, oedematous, non-painful, pruritic lesions that typically resolve within 24 hours and leave no residual markings.
Acute urticaria lasts less than 6 weeks and is often due to a hypersensitivity reaction to a specific trigger. Underlying viral infections are also a common cause of acute urticaria, particularly in children. Acute urticaria is generally self-limiting.
Chronic urticaria is characterised by daily or near-daily episodes of hives occurring for 6 weeks or more and has a complex aetiology.
Angio-oedema is swelling involving the deeper layers of the subdermis and occurs in association with urticaria in about 40% of cases. It can also occur in the absence of urticaria.
Angio-oedema involving the face or neck can potentially compromise the airway and requires prompt airway management.
Diagnosis of urticaria and angio-oedema is based on history and physical examination; diagnosis of chronic urticaria and hereditary angio-oedema may involve additional laboratory testing, depending on the history.
Referral to a specialist may be appropriate, especially in cases of chronic urticaria and chronic or hereditary angio-oedema.
Antihistamines are the mainstay of therapy for both acute and chronic urticaria. For patients who do not respond to antihistamines, additional treatment options include omalizumab and immunomodulatory medications.
Specific treatments are available to abort acute attacks and for longer-term prophylaxis of hereditary angio-oedema.
Urticaria (also called hives) consists of erythematous, blanching, oedematous, non-painful, pruritic lesions that develop rapidly, usually over minutes. Urticaria typically lasts less than 24 hours and leaves no residual skin markings upon resolution.
Approximately 40% of episodes of urticaria have associated angio-oedema. Angio-oedema is a sudden, pronounced swelling of the subdermis or mucous membranes. It may be painful, rather than itchy, and last up to 72 hours. The swelling primarily affects the face, lips, mouth, upper airway, genitals, and extremities.
Urticaria, with or without angio-oedema, may be acute or chronic. Acute episodes, which occur over a period of less than 6 weeks, are usually caused by a specific stimulus, and are self-limiting. Chronic episodes occur over a period of 6 or more weeks and are rarely attributable to a specific stimulus.
Angio-oedema can also occur in the absence of urticaria. This is a separate clinical entity, requiring a different diagnostic approach. Patient history, physical examination, and laboratory investigations are used to determine whether angio-oedema is drug-induced, hereditary, or acquired.
History and exam
Key diagnostic factors
- erythematous oedematous lesions
- resolution within 24 hours
- swelling of face, tongue, or lips
Other diagnostic factors
- blanching lesions
- positive family history
- female sex
- exposure to drug trigger
- exposure to food trigger
- recent viral infection
- recent insect bite or sting
1st investigations to order
- FBC with differential
- erythrocyte sedimentation rate (ESR)
- C4 level
Investigations to consider
- thyroid-stimulating hormone (TSH)
- antinuclear antibodies (ANA)
- skin prick testing
- allergen avoidance diet
- serum tryptase
- skin biopsy
- C1 esterase inhibitor level
- C1 esterase inhibitor function
- C1q levels
- specific IgE to suspected allergen
acute urticaria ± angio-oedema
chronic urticaria ± angio-oedema
drug-induced angio-oedema without urticaria
idiopathic angio-oedema without urticaria
- Atopic dermatitis
- Guideline for the definition, classification, diagnosis, and management of urticaria
- Guidelines for the management of people with chronic urticaria
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