Occasionally they may be associated with autoimmune diseases, parasitosis, malignancy, or other causes. Note the raised, red welts with sharp, obvious borders. Some of these welts have joined together, a process referred to as coalescence. Hives may cover large areas of the body. The capillaries dilate which causes a welt, and fluid oozes into the surrounding tissue, causing swelling.
Histamine also causes intense itching.
The majority of urticaria develop as a result of allergic reactions. The majority of urticaria develop as a result of allergic reactions. The majority of urticaria develop as a result of allergic reactions. The majority of urticaria develop as a result of allergic reactions.