Towards a more complete standardization of mite allergen extracts.

mite allergens. Although mites were first grown on human skin scales collected from barber shops and on yeast [1] , other food media used included fish food flakes, dried Daphnia, dog food, rodent chow, several cereal preparations, and even mold cultures [2] . Due to their position in the trophic chain, mites mainly feed on proteins found in house and mattress dust. A supplement of yeast is also important to complement the intake of micronutrients. The ingestion of a high-protein diet is a common determinant and is needed for their proliferation. Several food media are currently being used to grow mites. There are general recommendations to avoid the use of human-, and other animal-, derived proteins. Food media currently used in Europe and the USA include autoclaved pork liver powder and yeast, brine shrimp eggs and yeast and wheat germ. Other companies produce mites grown on wheat germ supplemented with amino acids (resembling the composition of human stratum corneum) and baker’s yeast [3] . For the preparation of allergen extracts, the United States Food and Drug Administration (FDA) only allows the use of mite cultures containing more than, or at least, 99% pure mites (see FDA website). In Europe, there are also general recommendations by the European Medicines Agency [4] , which state: ‘The cultivation method Dermatophagoides pteronyssinus and D. farinae are among of the most important sources of clinically relevant allergens worldwide. Mites are cultured in the laboratory and the material harvested from large scale cultures is used to prepare mite extracts for diagnosis, immunotherapy of mite-allergic individuals and allergy and immunology research. Kilogram quantities of mite cultures are harvested yearly and millions of individuals are diagnosed with allergen extracts and treated with mite vaccines. Although there are some general recommendations on the subject, mite cultures may be used as whole cultures, thus containing more fecal material, or sieved, containing more purified mites. Both raw materials are used. Currently, there is a clear trend towards using more purified cultures to avoid the presence of food medium. The use of a well-defined nonallergic medium is also warranted. D. pteronyssinus and D. farinae have a global distribution. The allergenicity of other species, such as Blomia tropicalis , Lepidoglyphus destructor and Tyrophagus putrescentiae , has also been demonstrated. Extracts of these species are also commercially available in many countries. Although the allergenicity of house dust was known for many years, only in the mid-1960s did it become clear that house dust mites were the main source of house dust Published online: August 30, 2012