Allergy

An allergy is an immune system overreaction to a normally harmless substance, such as pollen, food proteins, dust mites or animal dander, that triggers symptoms on exposure.

On first contact the immune system of a susceptible person makes IgE antibodies against the allergen; on later contact the allergen binds those antibodies on mast cells, which release histamine and other chemicals. The result ranges from sneezing, itchy eyes, hives and eczema to wheezing, swelling and, in anaphylaxis, a rapid whole-body reaction that requires emergency care. Dogs and cats develop allergies too, most often showing as itchy skin, ear infections and licking of the paws.

Allergies are assessed by history that links symptoms to exposures, skin prick or blood tests for specific IgE, and, for foods, supervised elimination and challenge. Hemp and cannabis products can themselves cause allergic reactions, and carrier ingredients derived from coconut or tree nuts and botanical additives are potential allergens, which is why ingredient lists and allergen statements matter. Cannabinoids have been studied in cell and animal models of allergic inflammation, and human evidence is early.