Or “hives” – itchy plaques or papules (weals), with surrounding flare, typical of histamine reaction in skin. Urticaria can also be accompanied by angioedema – although angioedema on its own may point to hereditary angioedema.
Not always allergy, although it is the classic rash of type 1 (histamine and IgE mediated) allergy. Can be inducible or inflammatory. Can be cyclical (catamenial=related to female hormones) and can be chronic. And often, no underlying cause can be found.
Various kinds of physical stimuli can trigger urticaria, including:
- Heat (including exercise and emotion)
- Sunshine (solar)
- Water (aquagenic)
This group of conditions is also called cholinergic urticaria. Some tests have been suggested eg ice cube.
- Atopic dermatitis
- Chronic or recurrent infection (consider occult eg dental)
- Erythema marginatum (as in rheumatic fever, but also a prodrome to HAE)
- Erythema multiforme
- Drug reactions
- Polymorphous light eruption
- Thyroid disorders
- Cutaneous mastocytosis
- Systemic lupus erythematosus
- Cryopyrin (autoinflammatory) disorders
- Urticarial vasculitis (often spectacular, bruising develops)
- Autoimmune urticaria (caused by autoantibodies vs FC epsilon RI alpha, but antibodies do not correlate well with symptoms)
- Oestrogen, progesterone and pregnancy related dermatoses
And if everything else excluded, that leaves Chronic idiopathic urticaria – questionnaire on quality of life available. [EMJ. 2019;4:39-47.]
Basophil histamine release assay and autologous serum skin tests suggested, 25% of all chronic urticaria patients are positive for one and/or other, but 50% are negative for both – so struggling for a diagnostic standard.
- FBC, CRP, ESR to look for infection
- H pylori – chronic inflammation eg gastritis might be a cause in itself.
- Functional autoantibodies eg Thyroid, ANA
- TFTs, thyroid abs
- Pseudoallergen (additives, flavourings, colourings) free diet for 3 weeks
- Tryptase – systemic mastocytosis?
- C3/4 – if suspected urticarial vasculitis, and if reduced, measurement of anti-C1q antibodies [BSACI urticaria guideline]
- Biopsy – but for mastocytosis, bone marrow aspirate most sensitive!
Specific tests: ice cube, flannel, dermatographism, hot bath, exercise. See Magerl M, et al. EAACI/GA2LEN/EDF/UNEV consensus panel recommendations. Allergy 2009;64:1715–1721.
For acute, non-sedating H1 blockers, else steroids. Evidence for H2 blockers eg ranitidine very weak.
For chronic, good evidence for ciclosporin. Nonsedating AH effective in <50% of patients. Guidelines recommend up to 4x updosing (weak evidence). Weak evidence too for steroids, zafirlukast, cimetidine, MTX etc. Omalizumab could be worthwhile.
EAACI 2012, RCPCH urticaria pathway