Urticaria – [Never lasts > 24h – consider dermatology review] [2 types – acute and chronic]
- Acute
- Commonly viral, drug – esp. NSAIDs
- May be food allergy if clear history
- Non-recurring, highly unlikely to be allergy
- Chronic [>6w] [Majority can be managed in primary care]
- Common triggers – Viral, physical – pressure, temperature; stress, additive, colourants – [cause not usually identified ?autoimmune]
- [Tests unlikely to be beneficial] [If patients want referral do Total IgE & IgE for nut and food mix]
- Usually burns out by 2y
- Treatment
- Avoid trigger & NSAID [consider aspirin to clopidogrel]
- Regular non-sedating antihistamine – higher dose may help – [Cetirizine] [Fexofenadine] [Loratidine]
- Add sedating antihistamine – [Chlorpheniramine] [Hydroxyzine]
- Angioedema without urticaria
- Usually due to NSAID or ACEi
- ACEi effect can last several weeks after stopped – if recurrs >6w after stopped, consider another cause
- Hereditary or acquired angioedema [impaired function of C1 inhibitor]
- Before referral – Complement C4 bloods, myeloma screen & C1 esterase inhibitor concentration
- Usually due to NSAID or ACEi
- Referral to allergy clinic
- [Life threatening symptoms e.g. laryngeal spasms] [atypical urticarial lesions – e.g. urticarial vasculitis] [severe anaphylactoid-type reactions] [suspected hereditary or acquired angioedema] [Oedema <40y]
- No response to NSAID & ACEi avoidance for 6w
- Response failure to 2 regular different antihistamine combinations each for 6-8w
Allergic food reactions
- Presentation
- Symptoms – [within 2h] [almost always urticaria & angioedema] [often GI/Resp. disturbance] [adult onset is rare]
- Usually eggs, milk, peanuts & other nuts, soya, fish & seafood
- Initial investigation – IgE specific bloods [high -ve predictive value]
- Not food intolerance [e.g. bloated, diarrhoea] [Poorly understood] [do not refer to allergy specialist]
- Referral to allergy clinic
- True food allergy suspected
- First take Total & specific IgE first for common food mix & nut mix & others as implicated
- True food allergy suspected
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