A15. Urticaria

Also called hives
Etiology
- Basically anything, but often idiopathic
- Physical urticaria
  - Most common
  - Pressure
  - Dermatographic urticaria
  - Elevated/decreased body temperature
  - Sweating
  - Sun-exposure
- Allergic urticaria
  - Foods
    - Fish
    - Shellfish
    - Nuts
    - Eggs
  - Drugs
    - Penicillin
    - Aspirin
    - ACE inhibitors
    - NSAIDs
  - Inhalants
- Autoimmune urticaria
- Vasculitic urticaria
- Infectious urticaria
- Others
  - Insect bites/stings
  - Pregnancy
  - Exercise
  - Additives to food, dermatological products, soaps, etc.
Classification
- Acute < 6 weeks
  - 95% of acute cases resolve
  - 5% progress into chronic
- Chronic > 6 weeks
  - 25% of all urticaria patient
  - Etiology can’t be established in many cases
Pathomechanism
- Local capillary vasodilation and transudation of fluid -> intradermal oedema
- Mostly due to histamine, bradykinin, complement factors
- Mast cell degranulation occurs
  - In some cases, due to hypersensitivity type I
Clinical features
- Pruritus
- Diffuse urtica/wheals
  - Circumscribed, sharply demarcated
  - Erythematous plaques, sometimes with central clearing
  - Individual lesions disappear after 24 hours
- Angioedema may also occur
Diagnosis
- Extensive history is essential
  - Any new dermatological products, drugs, etc.
- Lab tests
  - Inflammatory markers
  - Autoantibodies
  - Infections
- Prick test
- Patch test
Treatment
- For chronic
- Oral antihistamines
- Cyclosporine
- Leukotriene antagonist
- Omalizumab (anti-IgE)