Which skin condition involves the presence of large, raised red welts on the skin?

Urticaria, commonly known as hives, is characterized by the presence of large, raised red welts on the skin, which can vary in size and shape. These welts arise as a result of an allergic reaction or irritation that causes the release of histamine and other chemicals in the body. This process leads to localized swelling and redness due to increased blood flow and fluid accumulation in the dermis, resulting in the characteristic appearance of hives.

The condition often presents with itching and can be triggered by various factors, including food, medications, insect bites, or environmental factors. The raised weals may resolve on their own within a few hours or persist for a longer duration, depending on the underlying cause and individual sensitivity.

The other conditions mentioned do not present with the same symptomatology as urticaria. For example, xanthomas appear as yellowish plaques or nodules due to fat accumulation, keloid scars are raised scars resulting from excessive collagen formation at the site of a wound, and cellulitis is a bacterial skin infection that causes redness, swelling, and warmth, but does not typically create the distinct welts that characterize urticaria.