Rash on chest is not frequent,it comes and goes. the up back of the shoulder has a thin rash/acne/blackheads frequent skin reaction.

Vague: The cited symptoms are too vague to provide for much of a response. Skin issues most often require direct observation for assessment. Past history, recent exposures, change in foods or products, etc are relevant. You are welcome to start over with a detailed description of the rash (size,shape,raised/not, color,etc) but this is likely something that will pass or need to be examined.