DDx ⬇
- Vasculitis
- Erythema multiforme
- Contact dermatitis (eg, poison oak or ivy)
- Pityriasis rosea
- Erythema migrans (Lyme disease)
Related DDx ⬆ ⬇
Etiology ⬆
- Arthropod bites (insect bites)
- Drugs (nonallergic), eg, codeine, morphine
- Physical factors: heat, cold, solar, pressure, water, vibratory
- Cholinergic urticaria: exercise, excitement, hot showers
- Drugs (allergic): penicillin, aspirin
- Other allergic causes: feathers, dander, shellfish, tomatoes, strawberries, vaccines, chemicals, cosmetics
- Infection, eg, otitis media, sinusitis, hepatitis
- Serum sickness
- Angioedema: complement-mediated (hereditary or acquired), ACE inhibitors