Effects of chitin and chitosan particles on BALB/c mice by oral and parenteral administration.

Chitin and chitosan were administered orally and parenterally into mice and their toxicity was investigated. When 5 mg of chitin were injected intraperitoneally every 2 weeks over a 12-week period, the mice were apparently normal, but histologically, many macrophages with hyperplasia were observed in the mesenterium and foreign-body giant-cell-type polykaryocytes were observed in the spleen. The polykaryocytes were also observed in the spleen of the mice injected subcutaneously with 5 mg of chitin, but no other changes were observed. When 5 mg of chitosan were injected intraperitoneally, the body weights of the mice decreased significantly and inactivity was observed in the fifth week. Histologically, many macrophages with hyperplasia were observed in the mesenterium. Subcutaneous injection of 5 mg of chitosan did not evoke the general and cellular abnormalities. Oral administration of 5% chitosan via a casein diet caused mouse body weights to decrease and also decreased the number of Bifidobacterium and Lactobacillus in normal flora of the intestinal tract. These results indicate that special care should be taken in the clinical use of chitin and chitosan over a long time period.