Urticaria

General paediatrics, Immunology

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.

Inducible

Various kinds of physical stimuli can trigger urticaria, including:

  • Heat (including exercise and emotion)
  • Cold
  • Sunshine (solar)
  • Water (aquagenic)

This group of conditions is also called cholinergic urticaria.  Some tests have been suggested eg ice cube.

Differential

  • 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)
  • Mastocytosis
  • 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[1]:39-47.]

Diagnosis

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.

Consider:

  • 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.

Treatment

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