The minimum lethal oral dose of dimethicone 200 (50 cs), dimethicone 550 (75 cs), dimethicone in rats ^L1770.

A 76-week dietary toxicity study of a silicone antifoam compound (94% polydimethylsiloxane silicone oil and 6% silicone dioxide) was performed in mice. Three groups were given diet containing 0, 0.25%, or 2.5% of the test article. The dose levels in the treatment groups were estimated to be 580 and 5800 mg/kg/day. Mortality was increased in the 5800 mg/kg/day females. No target organs of toxicity were observed. The no-effect dose was 580 mg/kg/day. This study is of limited usefulness for assessing the toxicity of dimethicones, due to the small number of organs/tissues that were examined ^L1770.

In one clinical study, 145 subjects were treated with either NYDA (dimethicone )or with a permethrin-based lice product. The number of subjects experiencing any adverse events was similar in both groups. In the NYDA group, 29 adverse events were reported in 25 subjects. All except two adverse events were categorized as being unrelated to the lice treatment (e.g., superficial wound after a fall, otitis externa following swimming in a pool). Two patients in the NYDA group experienced ocular irritation after treatment when the product entered the eyes. The irritation resolved spontaneously in both cases after rinsing the eyes with clean water ^L1774.