The research purpose was to experimentally investigate the effect of allicin administration on the levels of main type 1 diabetes (IDDM) autoantibodies which are anti-islet cell antibodies (ICA) with an attempt to find a relation between this immunological effect and histological and/or biochemical findings. We have evaluated, with the help of ELISA kits, the levels of ICA and serum insulin in male Sprague-Dawley rats with Streptozotocin-induced IDDM in addition to pancreatic histological findings. The four groups (6 rats each) under study received or not different intraperitoneal doses of allicin for a period of 30 days. Daily intraperitoneal administration of allicin (either at as low dose of 8 mg/kg or high dose of 16 mg/kg) for up to 30 days to type 1 diabetic rats effectively reduces levels of anti-islet cell antibodies and in addition, reduced the level of insulin due to damaged Langerhans islet cell was significantly increased in the serum due to a repairing tissue process in pancreatic tissues. These experimental results suggest that allicin treatment has a therapeutic protective effect against autoimmune reactions occurring in IDDM. The data may provide new strategies for using allicin to be recommended as an excellent candidate in the clinical management, control, and prevention of IDDM.