wheal-and-flare reaction

The wheal-and-flare reaction is a type of acute, localized skin response, often associated with allergic reactions. It is characterized by a central raised area (wheal) caused by local swelling, surrounded by redness (flare) due to dilated blood vessels. This reaction is typically accompanied by itching and is a result of histamine release within the skin.12

Common triggers for this reaction include allergies to foods like shellfish, strawberries, and nuts, as well as certain drugs such as penicillin. Physical factors like cold, exercise, and sunlight can also provoke this response. In the context of Type I hypersensitivity, a wheal-and-flare reaction can occur when an antigen is injected beneath the skin, leading to swelling and redness. Antihistamine medications are often effective in treating these reactions because histamine is a key causative agent.123