Table 2.
Recommended investigations in urticaria according to type and subtype
| Type | Subtype | Initial tests | More extensive tests |
|---|---|---|---|
| Spontaneous urticaria | Acute spontaneous urticaria | None | None* |
| Chronic spontaneous urticaria | CBC with differential and ESR or CRP | (i) Allergen skin testing, and measurement of allergen-specific IgE levels are seldom required in CSU. Measurement of IgG levels to foods has no diagnostic value. (ii) functional autoantibodies; (iii) thyroid hormones and autoantibodies; (iv) physical tests; (v) tryptase; (vi) autologous serum skin test; (vii) lesional skin biopsy | |
| Inducible urticaria | Cold urticaria | Cold provocation and threshold test: apply an ice cube to the skin for 5 min, or, if available, use a TempTest; urticaria appears on re-warming | CBC with differential and ESR/CRP cryoproteins |
| Delayed pressure urticaria | Pressure test | None | |
| Heat urticaria | Heat provocation and threshold test | None | |
| Solar urticaria | UV and visible light of different wave lengths | Rule out other light-induced dermatoses | |
| Symptomatic dermographism | Elicit dermographism by stroking skin firmly with a tongue depressor or, if available, use a FricTest | None | |
| Aquagenic urticaria | Wet cloths at body temperature applied for 20 min | None | |
| Cholinergic urticaria | Exercise and hot bath provocation | None | |
| Contact urticaria | None |
CBC, complete blood count; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; NSAID, non-steroidal anti-inflammatory drug.
*Acute urticaria and angioedema can also occur in the context of anaphylaxis. Such patients should be tested to allergens relevant to the history of their anaphylactic episode, eg. foods, stinging insect venoms or medications (references [2,3]).