Urticaria, commonly referred to as hives, appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very pruritic. It may be acute (< 6 weeks) or chronic (>6 weeks). Urticaria may be confused with a variety of other dermatologic diseases that are similar in appearance and are also pruritic; usually, however, it can be distinguished from these diseases by an experienced clinician.

Chronic hives usually aren’t life-threatening. But the condition can be very uncomfortable and interfere with sleep and daily activities.

Classification of urticaria

Urticaria is classified according to its duration.

• Acute urticaria (< 6 weeks duration, and often gone within hours to days)
• Chronic urticaria (> 6 weeks duration, with daily or episodic weals)

Chronic urticaria may be spontaneous or inducible. Both types may co-exist.

Inducible or physical urticaria includes:

• Symptomatic dermographism
• Cold urticaria
• Cholinergic urticaria
• Contact urticaria
• Delayed pressure urticaria
• Solar urticaria
• Heat urticaria
• Vibratory urticaria
• Aquagenic urticarial