Urticaria – also known as hives, weals, welts or nettle rash – is a raised, itchy rash that appears on the skin. It may appear on one part of the body or be spread across large areas. The rash is usually very itchy and ranges in size from a few millimetres to the size of a hand. Although the affected area may change in appearance within 24 hours, the rash usually settles within a few days.