Classification of urticarial diseases.
| Forms | Subforms | Definition |
| Spontaneous urticaria | Acute spontaneous urticaria (asU) | Spontaneous wheals and/or angioedema (vascular edema) <6 weeks |
| Chronic spontaneous urticaria (csU). | Spontaneous wheals and/or angioedema >6 weeks. | |
| Physical urticaria | Cold contact urticaria | Triggering factors may include cold objects, air, liquid, wind |
| Delayed pressure urticaria | Triggering factor is static pressure; wheals appear with a 3-12 hour delay | |
| Heat contact urticaria | Triggering factor is localized heat | |
| Light Urticaria | Triggering factor is UV and/or visible light. | |
| Urticaria factitia/symptomatic urticarial dermographism. | Triggering factor is shear forces; wheals appear after 1-5 minutes | |
| Vibratory urticaria/angioedema | Triggering factor is vibration (e.g., jackhammer) | |
| Other types of urticaria | Aquagenic urticaria | Triggering factor is water |
| Cholinergic urticaria | Triggered by elevation of core body temperature (e.g., from exertion, spicy foods) | |
| Contact urticaria | Triggered by contact with urticariogenic substances | |
| Exertion-induced urticaria/anaphylaxis | Triggering factor is physical exertion, plus food intake if necessary |
