Urticaria, commonly known as hives, is a skin condition that affects about one in five people at some point in their lives. It causes intensely itchy, raised patches called weals that may be round, ring-shaped, or merge together.

Hives can appear anywhere on the body and often develop after scratching the skin. Although uncomfortable, the welts themselves are usually temporary and may fade within 24 hours.

The condition occurs when mast cells release histamine and other chemicals into the bloodstream. These substances cause fluid to leak from small blood vessels in the skin, leading to swelling and redness.

Urticaria is frequently accompanied by angio-oedema, a deeper swelling under the skin. This typically affects areas such as the lips, eyelids, or inside the mouth and is usually more painful than itchy.

If angio-oedema occurs without hives, it may indicate hereditary angio-oedema, a separate condition that requires different testing and treatment. This form is not linked to histamine release.

Based on duration and triggers, urticaria is classified into several types. Acute urticaria lasts up to six weeks and often has an identifiable cause, while chronic urticaria persists longer and usually has no clear trigger.

Physical urticaria is caused by external factors such as scratching, cold exposure, pressure, sunlight, or increased body temperature. Common triggers across all types include allergies, infections, stress, and certain medications.

Most cases resolve without treatment, but persistent symptoms may require antihistamines, steroid tablets, or soothing creams. People with allergies or underlying health conditions are more prone to hives, making awareness and proper care essential.