Urticaria (hives / wheals)

Aetiology

• Viral: e.g. EBV, hepatitis (A,B &C), HSV
• Bacterial: e.g. Streptococcal
• Parasitic
• Insect bites (last longer that 24hrs)
• Drug rxn: Urticarial rash may appear a 14/7 after stopping penicillin

Rash

Clinical

• Itchy++, raised (palpable), blanching (with pressure) wheals
• Rash is transient (hours) and moves location/shape
• Dermatographism — urticarial lesions with light scratching
• No permanent scarring / pigmentation (cf "beware")
• Many have oedema of eyelids, perioral and feet / extremities

Beware

• Angioedema of the lips: suggests autoimmune aetiology:
  • Check thyromegaly, rheumatoid arthritris, SLE etc
• Ecchymosis/pigmentated lesions: suggest vasculitis
• Systemic signs of wt loss, arthralgia, lymphadenopathy
• Any signs jaundice (cholestatic itch)?
• SIRS or other indicators of sepsis?

DDx (itch)

• Erythema multiforme
• Contact dermatitis (slower onset and offset)
• Atopic dermatitis
• Insect bites (fixed location)
• Drug reaction

Management

• Avoidance of trigger
• H1-receptor blockers:
  • Loratadine or cetirizine (non-sedating)
  • Chlorphenamine or promethazine only if sedation needed (itch insomnia)
• Education re anaphylaxis (± adrenaline prescription)