In a controlled human study (Industrial Bio-Test Laboratories, Inc. 1973), 52 subjects received a series of nine dermal applications of antimony trioxide over a 3-wk period. The antimony trioxide was applied for 24 hr; the dose was not reported. Two wk after the series of applications, a single dose of antimony trioxide was applied. After each application, skin reactions were evaluated. No skin reactions were observed over the course of the study, suggesting that antimony trioxide is neither a skin irritant nor a sensitizer.

Dermal exposure to antimony trioxide generally did not cause dermatitis in tested animals. Only mild skin irritation was observed even after repeated or prolonged exposure to large quantities of antimony trioxide (2–25 g antimony trioxide/kg) in rabbits (Gross et al. 1955a; Ebbens 1972). Skin edema was reported in one study in which antimony trioxide was applied to rabbits in corn oil (8 g antimony trioxide/kg for 24 hr) (Myers et al. 1978). However, that study is limited in that there was no solvent control group, and data on severity and number of animals responding was lacking. In a study by Haskell Laboratory (Haskell Laboratory 1970a), a suspension of 12, 31, or 61 mg antimony trioxide/kg in a fat/acetone/dioxane mixture was applied to intact shaved skin (all doses) or abraded skin (31-mg/kg group only) of 10 albino guinea pigs. The exposure duration was not reported. Irritation was not seen in any of the treated animals. In another study by Haskell Laboratory (1970b), 24 or 49 mg/kg antimony trioxide (suspended in a similar mixture as above) was applied to the intact shaved skin of guinea pigs. One day after the treatment, mild erythema was observed in 2/10 and 5/10 animals treated with 24 mg antimony trioxide/kg and 49 mg antimony trioxide/kg, respectively. All of the responses had disappeared 2 d after the initial dosing.

As mentioned under the Irritation section, no skin reactions were observed in the controlled human study conducted by Industrial Bio-Test Laboratories, Inc. (1973), indicating that antimony trioxide is not a skin sensitizer.

Haskell Laboratory (1970a, b) treated groups of five guinea pigs with nine dermal applications of 31 mg antimony trioxide/kg (25%) or 49 mg antimony trioxide/kg (50%) in a fat/acetone/dioxane mixture on shaved and abraded skin, or four intradermal injections of 1 mg antimony trioxide in either acetonedimethyl phthalate or propylene glycol solutions, over the course of 3 wk. After a 2-wk rest period, each group of animals received challenge applications of the suspensions on both intact and abraded skin. Sensitization was not observed in any of the test animals.