Urticaria, also known by the name hives, is an allergic reaction that results in skin rashes in the form of pale red and itchy bumps, often accompanied by a burning sensation. Rashes that persist for a period of six weeks or lesser are caused by allergic triggers, while those lasting even longer than that are caused by non-allergic triggers.

While the researchers are unsure about the exact cause of urticaria, they point at autoimmunity and acute viral inflammation as possible reasons. Other causes include exercise, temperature extremes, sunlight, and friction.

There are two types of urticaria:
• 1. Acute urticaria: Swelling that lasts less than six weeks is termed as acute urticaria. Triggers that can cause acute urticaria include foods such as fish, tomatoes, fish, eggs, berries, wheat and milk. Besides that, certain medicines, internal diseases and insect bites too are likely culprits.
• 2. Chronic urticaria: Swelling that persists more than six weeks is called chronic urticaria. Most likely causes are autoimmunity, malignancy and hormonal disorders.