Papular rashes (1)
Acute urticaria affects 10% of the population at some time.
Adverse stimulus l mast cell degranulation l histamine release l localized vasodilatation and ‘rise’capillary permeability.
Usually idiopathic or triggered by recent viral infection. Other causes in-clude:
• Allergens (e.g. drugs, foods, inhalants, insect bites).
• Trauma (physical urticarias), e.g. dermographism due to light skin trauma (commonest), pressure, cold, heat, sunlight.
Chronic urticaria (defined as acute urticaria not resolving after 2mths) is idiopathic in >90%, but may be caused by:
· Chronic bacterial, fungal (e.g. oral Candida), or parasitic infection.
· Rarely, ingested food dyes.
• Rapidly developing erythematous eruption with raised central white wheals and occasionally local purpura.
• Any part of body can be affected and often itchy.
• Lesions last 4–24hr.
• May have associated fever and arthralgia (serum sickness).
Apart from good history investigation is usually not necessary. Skin prick testing is rarely helpful. If chronic, consider:
• throat swab (streptococcus);
• urine culture;
• exclude threadworms;
• food and symptom diary.
• Oral antihistamines.
• Oral prednisolone, short course if severe.
Avoid triggering factors, e.g. ingested food dyes and non-steroidal drugs.
Variant of urticaria with significant swelling of subcutaneous tissues, often involves lips, eyelids, genitalia, tongue, or larynx. If severe, may cause acute upper or lower respiratory tract obstruction and may be life-threatening.
As for urticaria. Hereditary angioedema is a rare AD condition caused by active C1-esterase inhibitor deficiency.
As for urticaria. If hereditary angioedema is suspected then measure serum C4 complement level initially.
• Give facial oxygen.
• IM 0.1mL/kg adrenaline 1:10 000.
• IM/IV hydrocortisone 12-hourly.
• Nebulized salbutamol.
In severe and recurring cases of hereditary angioedema, tranexamic acid or anabolic steroids (e.g. danazole boosts liver production of C1-esterase inhibitor) are effective, but the latter is rarely used in childhood due to its androgenic effects.
Common pox virus infection affecting infants and young children. Presentation
Pink umbilicated (central dimple) papules. Usually affects moist areas, but can occur anywhere. Exacerbated by active eczema or topical steroids.
None if uncomplicated as usually spontaneously resolves within a year. If problematic:
·Treat any associated eczema.
• Pinch forcep liquid nitrogen cryotherapy.
• Lesion curettage.
• Application of benzoyl peroxide 5% daily.