It has been noticed that kids usually eat and drink food containing food preservator and food colorants at the same time. This behavior has been attracted the attention to study the interaction between one of food preservatives ( sodium nitrite NaNO3) and one of bood colorants (sunset -yellow S.S.Yellow). The interaction of the limited dose of these two components resulted in a lethal dose. So, 1 /10 of this dose was used for 30 days and left for another 15 days post the last dose for recovery. Other group was supplemented with Nigella sativa ( N.S) oil in addition to the same mixture. Ingestion of (NaNO3 and S.S.Yellow) mixture significantly decreased rat's body weight, RBC and WBC counts, Hb%, Hct%, serum inorganic phosphorus, serum protein and serum albumin. Significant increases were observed in serum glucose, T3, T4, calcium, -GT, LDH, CPK, Alk.ph and cholesterol. Also cholesterol of brain, liver and heart were significantly elevated. No changes were recorded for; organ/body weight, respiratory rate, heart beats, rectal temperature, acid phosphatase activity, AST and ALT activities of serum and tissues, protein of tissues, serum globulin, and total lipids of serum and tissues, cholesterol of muscle and kidney and serum triglyarides. A complete recovery of most biochemical and haematological parameters was observed days after stoppage of the mixture or after administration of Nigella sativa oil. This study ringe bells of dangerous. The study showed also that even the permitted colourants and food preservatives when taken together or if taken in excessive quantity may be harmful. Therefore, provision should be made for quantities estimation of food additives in various food stuff.