What is a common sign of an allergic reaction recognized in dermatology?

Urticaria, commonly known as hives, is a prominent sign of an allergic reaction characterized by raised, itchy welts on the skin. This condition arises when the body releases histamine and other chemicals in response to an allergens, leading to swelling and changes in skin color. Urticaria can appear suddenly and may vary in size and shape, often accompanied by itching and, in some cases, a burning sensation.

In contrast, psoriasis is a chronic autoimmune condition that leads to red, scaly patches on the skin and is not directly linked to allergic reactions. Fungal infections are caused by fungi and present differently, usually manifesting through localized redness, itching, and sometimes peeling skin, but are not considered an allergic response. Acne is a common skin condition primarily related to hormonal changes and clogged hair follicles and does not stem from allergies. Thus, urticaria is distinctive for its association with allergic responses, making it the correct answer.