Standardized cat hair extract

Standardized cat hair extract is a biological preparation derived from the dander, hair, and saliva of the domestic cat (Felis catus), containing a complex mixture of proteins that trigger allergic reactions in sensitized individuals [1]. The primary allergen within this extract is Fel d 1, a secretoglobin protein that is responsible for approximately 60-90% of the total IgE-binding activity in cat-allergic individuals [1, 2]. Other significant components include Fel d 2 (cat serum albumin), Fel d 4 (a lipocalin), and Fel d 7 [1]. These proteins act as antigens that cross-link IgE antibodies on the surface of mast cells and basophils, triggering the release of inflammatory mediators like histamine, which cause symptoms of allergic rhinitis, conjunctivitis, and asthma [1, 4]. Clinically, the extract is utilized for both the diagnosis of cat allergy via skin testing and for allergen-specific immunotherapy (AIT) [3, 4]. AIT involves the administration of gradually increasing doses of the extract to induce immunological tolerance, characterized by the expansion of regulatory T cells and the production of IgG4 "blocking" antibodies that mitigate the allergic response upon natural exposure [4].

Other names

Cat hair extractFelis catus allergen extractStandardized cat hair extractCat dander extract

Allergen-specific immunotherapy (AIT) induces immune tolerance by shifting the immune response from a Th2 to a Th1/Treg profile and increasing the production of allergen-specific IgG4 blocking antibodies [4].