No adequate enteral sensitization models are available to study food allergy and allergenicity of food proteins. Using a previously described oral sensitization protocol to sensitize Brown Norway rats (BN) to food proteins, the influence of genetically-based strain-specific characteristics of the immune system on the outcome of oral sensitization studies was investigated. BN, Hooded Lister (HL), Piebald Virol Glaxo (PVG) and Wistar rats were daily administered 1mg of ovalbumin (OVA) by gavage dosing for 42 days without the use of an adjuvants. The highest OVA-specific IgG responses were detected in the BN rats followed by Wistar, HL and PVG rats. OVA-specific IgE responses were only detectable in the BN rats. The cellular immune response was examined by determination of delayed-type hypersensitivity (DTH) reactions in the animals. The response was most pronounced in the HL and Wistar rats. PVG and BN rats showed comparable DTH responses but the responses were significantly weaker than those observed in HL and Wistar rats. It was concluded that the genetic make-up of different rat strains influences the outcome of oral sensitization studies. In addition, using the described oral sensitization protocol, the BN rat seems to be the most suitable strain for inducing oral sensitization. Copyright (C) 1999 Elsevier Science Ltd.