This study was performed to evaluate the effect of individualized diet challenges consisting of allergen foods on disease activity in rheumatoid arthritis (RA) patients. Twenty patients with positive skin prick test (SPT) response for food extracts and 20 with negative SPT response were included. All patients were instructed to restrict the most common allergen foods during 12 days and then assigned into two groups according to SPT results. Food challenges were performed with all of the allergen foods in prick test positive group (PTPG) and with corn and rice in prick test negative group (PTNG) during 12 days. Allergen foods were then eliminated from PTPG patients' diet, while corn and rice were removed in PTNG. Clinical evaluations were performed after fasting (baseline), at the end of the challenge phase and reelimination phase. Stiffness, pain, physician's and patient's global assessment of disease activity, health assessment questionnaire (HAQ), Ritchie's index, serum amyloid A protein, erythrocyte sedimentation rate and C-reactive protein were determined. All of the disease variables, except HAQ, were increased with food challenges in PTPG. In PTNG, no significant change was observed in any of the variables except pain (P<0.05) and patient's global assessment (P<0.05). Our results showed that the individualized dietary manipulations may effect the disease activity for selected RA patients.