There are two testing methods for allergies:
1. Intradermal - "the injection of tiny amounts of grasses, pollens, and other irritating substances under her skin, followed by observation for signs of irritation...
2. In Vitro Serologic - "a blood sample analysis... has a high incidence of false positive results" (Sinclair, Leslie. "Oh, Those Allergies." Dog Fancy, Feb. 2004, 52).
"Check out the skin between toes and pads. Look for inflammation (indicated by redness or moisture).. Inflammation here may signal allergies, especially if your dog licks or chews her feet" (Susan Bertram. "Stepping Out." Dog Fancy, April 2004: 63).
Colby Glass, MLIS