What is a common sign that an individual may have an allergic reaction to a product?

Redness or swelling is a common sign of an allergic reaction to a product. When the skin comes in contact with an allergen, the immune system may respond by causing inflammation, which manifests as redness and swelling in the affected area. This reaction can occur within minutes to hours after the exposure, indicating that the body is reacting to something it perceives as harmful.

While dry skin without irritation, slight itching, and a healthy glow might be related to other skin conditions or reactions, they do not specifically denote an allergic reaction. Dry skin usually indicates a lack of moisture rather than an immune response, slight itching may occur for numerous benign reasons, and a healthy glow generally suggests good skin condition, not a reaction. Therefore, observably inflamed skin characterized by redness and swelling serves as a clear indicator of an allergic response.