Hives often appears as a raised, itchy rash. The medical name for hives is “urticaria.” People also call it welts, wheals, or nettle rash.

Hives can occur for many reasons, including exposure to an allergen or a physical trigger, such as pressure from tight clothing. It may also indicate an infection or other underlying health condition.

Hives can develop as a reaction to:

• an allergen
• another physical trigger, such as extreme temperatures
• an underlying health condition

Sometimes there is no clear reason why they occur. In the case of chronic hives, some experts believe that it may result from an autoimmune reaction, but they are still unsure. If hives occur in a dermatome, check the whole neurological segment.

It is not possible to catch hives from another person. However, in some cases, hives occurs with a contagious infection.

If a person has hives, they have a risk of developing a life threatening condition called anaphylaxis. Being aware of other symptoms of this condition, such as swelling of the face, tongue, or throat, a rapid heartbeat, or lightheadedness is important.

Anyone who might have anaphylaxis should receive urgent medical care.