Welts on the skin, also known as hives or urticaria, are a skin reaction that causes itchy bumps that range in size from small spots to large blotches. The welts can be skin-colored, reddish on white skin, or purplish on black and brown skin, and can be round, oval, or worm-shaped. They can be as small as a pea or as large as a dinner plate. Hives can be acute, lasting less than 24 hours, or chronic, lasting more than 6 weeks.

The welts that come with hives are caused by the release of immune system chemicals, such as histamine, into the bloodstream. Hives can be triggered by a variety of factors, including:

• Allergic reactions to food, medication, pet dander, pollen, bug bites or stings, or latex
• Overreaction to heat, sweat, or cold
• Stress
• Sunlight
• Pressure on the skin, such as from tight clothing or scratching
• Medical conditions, such as thyroid disease, infection, allergy, and cancer

Physical urticaria is another type of hives that is caused by something that stimulates the skin, such as cold, heat, sun exposure, vibration, pressure, sweating, or exercise.

Treatment for hives typically involves antihistamines or steroids. In some cases, hives can be life-threatening if swelling of the tongue or in the throat blocks the airway. If you experience welts on your skin, it is important to consult a healthcare professional to determine the underlying cause and appropriate treatment.