Urticaria are red raised bumps or welts on the skin. They can appear anywhere on the body and can look like tiny little spots or large interconnected bumps.
The red welts of Urticaria happen when mast cells in the bloodstream release the chemical histamine, which causes tiny blood vessels under the skin to leak. The fluid pools within the skin to form spots and large welts. This can happen for a number of reasons, but in many cases a cause is never identified.
Most often, Urticaria are associated with an allergic reaction, which can cause the skin to break out within minutes. Common allergies include:
- foods, especially shellfish, tree nuts, milk, and fruit
- medications and allergy shots
- pets and other animals
- insect bites and stings