Contact sensitization has been observed occasionally among acne patients during treatment with topical preparations of benzoyl peroxide. In the present work benzoyl peroxide was found to be a potent skin sensitizer in repeated insult patch tests. Similar results were obtained in tests with guinea pigs and human subjects and these results illustrate the value of predictive patch testing as a screening procedure for chemical agents to be distributed widely in consumer products for topical application to human skin.
Poole RL, Griffith JF, MacMillan FSK. Experimental Contact Sensitization With Benzoyl Peroxide. Arch Dermatol. 1970;102(4):400-404. doi:10.1001/archderm.1970.04000100048011