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
Allergic contact dermatitis primes and sensitizes the immune system for an allergic response, and an "elicitation phase", in which this response is triggered. As it involves a cell-mediated allergic response, ACD is termed a Type IV delayed hypersensitivity reaction, making it an exception in the usage of the designation "allergic," which otherwise usually refers to type I hypersensitivity reactions. Contact allergens are essentially soluble haptens (low in molecular weight) and, as such, have the physico-chemical properties that allow them to cross the stratum corneum of the skin. They can only cause their response as part of a complete antigen, involving their association with