What is a common sign of an allergic reaction to a cosmetic product?

A rash or hives is a common sign of an allergic reaction to a cosmetic product due to the body's immune response to an irritant or allergen present in the product. When the skin comes into contact with a substance to which someone is allergic, it can trigger inflammation and swelling, often resulting in raised, red welts known as hives or an overall rash.

This reaction is typically characterized by the body’s attempt to "fight off" the foreign substance, which causes discomfort and shows visible signs on the skin. Recognizing a rash or hives as a symptom is crucial for individuals to discontinue use of the product and seek appropriate medical advice to manage their reaction. Other signs of allergic reactions, such as dryness, redness, and itching, can also occur, but the presence of a rash or hives is particularly indicative of an allergic response specifically.