Amblyomma americanum mammalian meat and meat products. The allergy manifests as anaphylaxis — a life-threatening allergic reaction characterized by constriction of airways and a drop in blood pressure. This response is triggered by an IgE antibody to the mammalian oligosaccharide galactose-alpha-1,3-galactose (alpha-gal). As well as occurring in non-primate mammals, alpha-gal is also found in cat dander and in the drug cetuximab. Allergic reactions to alpha-gal usually occur 3–6 hours after consuming red meat, unlike allergic reactions to other foods, whose onset following consumption is more or less immediate, making it more difficult to identify what caused the reaction. Skin tests with standard
Dermatographic urticaria rapidly break down under physical pressure, which then causes an allergic-like reaction. Symptoms can be caused or induced by: The underlying cause of dermographism is not known, and it can last for many years without relief. The condition may subside and be effectively cured; however, it is often a lifelong ailment. It is not a life-threatening disease, and it is not contagious. Dermographism may occur in mastocytosis (systemic mast cell proliferation). Dermographism can be treated by substances which prevent histamine from causing the reaction (i.e. an antihistamine). These may need to be given as a combination of H antagonists, or