Background: Other researchers have reported that the specific immune response to subsequent antigen challenge is primed in newborn mice or rats dosed orally by gavage. We wanted to investigate if priming of a subsequent specific IgE response could be achieved by dosing newborn rats orally with ovalbumin and if this method could be used in an animal model for food allergy. Methods: Newborn Brown Norway rats were dosed with ovalbumin in the mouth (100 mug or 6 mg). As young adults, the animals were dosed by gavage for 35 days with 1 mg ovalbumin/day or once intraperitoneally with 100 mug. Control groups were dosed by gavage or intraperitoneally but not as neonates. Additionally, young adult rats were dosed with 1 mg ovalbumin/day in the mouth for 35 days. Sera from individual animals were analysed for specific IgE and specific IgG. Results: In all experiments with neonatal rats the specific IgE and IgG responses were decreased compared to the control groups, however, not always reaching statistical significance. A statistical significant decrease in the specific immune response was found in young adult rats dosed in the mouth as compared to by gavage. Conclusions: Dosing Brown Norway rats with ovalbumin in the mouth as neonates do not prime the specific immune response. The decrease in immune response found in our experiments when dosing newborn animals in the mouth in opposition to the priming seen by others when dosing by intra-gastric intubation may be explained by a dissimilar antigen presentation when dosing includes both oral mucosa and gut. Copyright (C) 2003 S. Karger AG, Basel.