The purity of allergenic extracts

The purity of allergenic extracts is usually taken for granted but we know that trace amounts of impurities may be the most important determinant causing clinical symptoms. We know that many commercial extracts are grossly contaminated with other allergens and this is easy to demonstrate by skin tests. Horse or dog scurf collected in the summer months will be contaminated by pollens. Patients can be shown to have organ specific inhalant allergic complaints due to one animal. Sometimes the allergenicity is at first only towards an antigen in the saliva, then skin antigen(s) and finally all organs of the body may cause allergic symptoms, so that urinary protein as well as serum albumin cause reactions to the patients. When collecting individual pollens, it is very difficult not to get these contaminated by other pollens. Named grass pollens will be contaminated by other grass pollens and fungal spores which are airborne at the same time. An extract which has been labelled plantain pollen will often be contaminated by 1% or more of grass pollen. A tree pollen such as Tilia is always grossly contaminated with other pollens. A mite extract has in it fish, human serum albumin from skin scales or horse, depending on the culture media used for feeding the mites. Animal scurf extracts are nearly always contaminated with mites. We can conclude that allergenic extracts are difficult to produce immunologically pure and they are often grossly contaminated.