What defines the condition known as hives?

Hives, also known as urticaria, are characterized by raised and itchy welts on the skin. This condition occurs due to an allergic reaction or other triggers that lead to the release of histamine and other chemicals from mast cells in the skin. These chemicals cause blood vessels to leak fluid, resulting in swelling and the formation of welts that can vary in shape and size. The itchiness associated with hives is a direct result of nerve endings being stimulated by the inflammation. This specific presentation of welts distinguishes hives from other skin conditions, making it essential for accurate diagnosis and treatment.

In contrast, the other options describe different skin conditions: thick patches of scaly skin relate to conditions like psoriasis or seborrheic dermatitis, a gradual loss of skin pigment can indicate vitiligo, and constant pain in the skin layers may be associated with conditions like shingles or other neuropathic pains. Each of these conditions presents with unique symptoms that are distinctly different from hives.