Hello and welcome to healthcaremagic One possibility that could be the reason for eruptions in your case is of pityrosporum folliculitis(caused by yeast). Pityrosporum folliculitis ITCHES a lot and is commonly seen in hot, humid weather conditions. Clinically both look the same except the itching part which is prominent in Pitryosporum folliculitis. Acne usually does nt itch or they itch only slightly. Pityrosporum Folliculitis is caused by proliferation of yeast, Malasezzia furfur. Exactly the same yeast has been implicated in the pathogenesis of dandruff/seborrheic dermatitis. The yeast can travel down the hair length to the back and chest and cause Pityrosporum Folliculitis of the back. The scalp, chest and back are rich in oil glands, therefore providing an ideal environment for the yeast to feed upon. In addition to the topical antifungal and an antidandruff shampoo, I would suggest an oral antifungal in your case e.g itraconazole 200mg once daily for a week to kill the yeast rapidly. Topiacal antifungal alone are not at all effective in Pityrosporum Folliculitis and patients need to be treated with oral antifungals. Topical antifungals can be used to prevent a relapse, rather. I hope this answers your query. regards