Benzoyl peroxide is one of the most used medicines in the treatment of acne. Many acne products on the market will contain this chemical substance including creams, lotion and gels. Benzoyl peroxide helps to heal acne by killing the bacteria which is responsible for acne infection and is known as P. acnes. As this bacterium is present everyone, it starts to infect the skin which leads to acne. Some of the symptoms of this infection are redness, irritation and swelling. As the benzoyl peroxide kills the bacteria, the surplus oil secretion from the skin dries out which may lead to some frequent side effects observed for this acne treatment.  The side effects of benzoyl peroxide in the treatment of acne are the skin irritation. Depending on the person’s skin texture, the irritation may range from little to more severe. People with very sensitive skin are cautioned very strongly to use the benzoyl peroxide medicine less often and they are also recommended to use low dosage of the medication. In some cases, the medicine having high dosage of benzoyl peroxide can causes more skin irritation which leads to overly reddened or even peel off. You have to consult the doctor if you have these symptoms.