Which symptom can indicate an allergic reaction to skin care products?

An allergic reaction to skin care products is typically characterized by symptoms that involve the skin's inflammatory response. The presence of redness, swelling, itching, and hives is a classic indication of such reactions. These symptoms occur because the immune system identifies certain ingredients in the products as harmful and responds by sending inflammatory signals, which lead to the dilation of blood vessels (causing redness and swelling) and the activation of nerve endings (leading to itching). Hives, or urticaria, manifest as raised, itchy welts on the skin, which are also common in allergic responses.

Other symptoms, such as skin dryness or excessive oiliness, do not directly indicate an allergic reaction. Skin dryness might occur due to dehydration or sensitivity without an allergic component, while excessive oiliness could result from hormonal changes or other factors unrelated to allergies. Similarly, increased hair growth is not a symptom associated with allergic reactions and may be linked to hormonal imbalances or specific medical conditions. Thus, the presence of redness, swelling, itching, and hives distinctly points to an allergic reaction rather than other skin conditions.