Experimental nickel sensitization in the guinea pig: comparison of different protocols

3 different sensitization protocols were compared for inducing delayed-type nickel contact hypersensitivity in guinea pigs. Open epicutaneous sensitization (OE) induced nickel allergy in 11/22 (50%) guinea pigs. When intradermal injections of Freund's complete adjuvant into the nickel-painted skin was added to the same protocol, 4/13 (31%) became sensitized. The guinea pig maximization protocol induced nickel allergy in only 7/31 (23%) of the animals. Compared with the 2 other methods, animals sensitized with open epicutaneous applications reacted more rapidly (maximum at 6 h) and strongly (2+ reaction in 12/22 of animals) in previous patch test sites upon systemic (i.p.) nickel challenge. Open epicutaneous sensitization of guinea pigs should be a useful model for studying cellular and immunological mechanisms in nickel contact sensitivity.