Allergenic food extracts. I. Methods of preparation: Results of a questionnaire

Abstract

The majority of allergists making their own food extracts used fresh uncooked food as the source of their raw material. The food was then ground or cut into smaller particles. The majority did not defat fruits and vegetables, but did defat meats, fish, nuts, grains, and spices. The majority used a weight-by-volume method of preparing their extracts and made dilutions of same for intracutaneous testing. Either alkaline extracting fluid (Coca's solution), glycerin saline, or buffered saline was used by the allergists in general for extracting purposes. Almost one third (forty-eight) of the allergists did not concentrate food extracts. Among these were twenty-three who used 50 per cent glycerin as an extracting fluid, which rendered it difficult to concentrate. Nearly all physicians sterilized their extracts by filtration through a Seitz type of pad. Several allergists did no sterility tests subsequent to Seitz filtration. Twenty-nine physicians incubated for intervals up to three days. Three-fourths (seventy-one) of the physicians reporting did not check the pH of the extract before or after Seitz infiltration. Most of these physicians did not dialyze the extract for pH adjustment. A weight-by-volume method of standardization for food extracts was used by a majority (sixty-nine) of the allergists. There were variations in procedure in that some used a dry weight and others a wet weight as the basis for the weight-by-volume method of standardization. A few concentrated their extracts, but most did not. The strength of the testing solution showed wide variations, even among persons using the same method of extraction and standardization. The numerous variables that have been presented are not being subjected to critical analysis. Further investigation is necessary to determine the effect of each of these variables upon the allergenicity of the final extract.