What is NOT a sign of an allergic reaction on the skin?

Darkening of existing moles is not commonly considered a sign of an allergic reaction on the skin. Allergic reactions typically manifest through various inflammatory responses, such as redness, swelling, pain, and itching, which are all indicators of the immune system responding to a trigger. In contrast, changes in moles, particularly darkening, can indicate other dermatological concerns, such as the potential for skin cancer, rather than an allergic reaction. Recognizing the difference is important for appropriate diagnosis and treatment, as allergic reactions require a focus on avoiding allergens and potentially using antihistamines, while changes in moles might necessitate further medical evaluation.