For decades food allergists have sought a simple, inexpensive test for food allergy. Intradermal tests of aqueous material have not proved reliable. When positive, they are probably only 10% accurate. The newer laboratory tests for food allergy are expensive and highly sophisticated. They are impractical for use in the laboratories of practicing allergists with whom individuals with a potential food allergy are most liable to consult. The RAST is capable of identifying only Type I of the Gell-Coombs' reaction classification. Since 1980, a patch test of individual foods suspended in dimethylsulfoxide has been used as a screen for sensitivity to foods. Controlled clinical studies suggest this might prove to be a valuable test for food allergy. Immune studies appear to confirm the accuracy and reliability of this inexpensive test. No systemic reactions have been observed in the 400 patients tested indicating it to be a safe procedure.