Fluoride pollution in drinking water is an international problem as the fluoride present is often at levels above acceptable limits. This study was done with an objective to determine the immunotoxic potential of sub acute exposure of sodium fluoride in Wistar rats with special reference to the Dinitroflurobenzene contact skin sensitivity test and pathological alterations in splenic
histoarchitecture. The rats were intoxicated orally to sodium fluoride at dose levels of 5, 25 and 50 mg/kg body weight, respectively for 28 days. On day 21 the external surface of right ear pinna of rats were sensitized to 40 µl of 2% Dinitroflurobenzene in vehicle followed by challenge application of 40 µl of 1% Dinitroflurobenzene in vehicle on day 25. The left ear pinna served as control and 40 µl of vehicle (4:1 acetone- olive oil) was applied. The increase in ear thickness (in mm) was measured with Engineers micrometer at 0, 6, 12, 24 and 48 h post challenge. The results revealed a dose dependent decrease (p < 0.001) in mean ear thickness (in mm) of sodium fluoride intoxicated rats following challenge application of 1% Dinitroflurobenzene in vehicle. The blood picture revealed dose dependent leucocytosis associated with neutrophilia and lymphocytopaenia. There was also dose dependent decrease in organosomatic index of spleen and severe depletion of lymphocytes in white pulp of spleen. This report highlights the proposition that prolonged exposure to fluoride contaminated drinking water is likely to result in immunotoxicity.