New techniques are needed to broaden the understanding of the food allergic response. The capacity of peanut extract to influence gene expression profiles was investigated in a Brown Norway rat model for food allergy. Brown Norway rats were sensitized to peanut extract (0, 1 and 10 mg/rat/d) by daily oral gavage and were dissected after 3, 7 or 14 days of exposure. RNA extracted from mesenteric lymph nodes of individual rats were hybridized against a common reference pool on Agilent whole rat genome (4*44k) arrays. The raw data were normalized and statistically analyzed using the statistical program R. A False Discovery Rate of 10% and a Fold Ratio of - 1.5 < or = Fold Ratio or Fold Ratio > or = 1.5 between the experimental groups and their respective control groups were applied. Differentially expressed genes were clustered into a heatmap. Functional annotation and GeneOntology term enrichment were examined. Furthermore, the involvement of the differentially expressed genes in specific cellular pathways was investigated with MetaCore. Gene expression changes, which were both dose- and time-dependent, were detected after sensitization to peanut. A total of 64 genes were differentially expressed, of which 60 were up-regulated and four were down-regulated. These changes were related to the regulation of immunological processes, most notably increased cell division. The findings indicate that responses to peanut include proliferation of immunologically relevant tissues, which can be identified by analysis of gene expression profiles. This may lay a basis for further research into possibilities for discrimination of allergenic from non-allergenic proteins.