What causes a severe acne breakout on the chest?

You may never know. Acne often flares without explanation. Acne on the trunk usually requires at least one systemic medication. If you're a female, the oral contraceptive pill may clear you if it's right for you. Or a combination of topical benzoyl peroxide and a systemic antibiotic for a while may be all you need to get clear. Acne's not curable but eventually remits. Best wishes.

Related Questions

How do I get rid of acne scars in my forehead and pimples on my chest? I always had clear skin but for the past 4 months I've been getting breakouts

Acne scars. One important factor is prevent new scars-get your acne under control. Find a dermatologist to tackle that with you. Most treatment to improve the appearance of acne scars use special technology to remodel the skin. The device I use to treat acne scars is called ematrix--see for info: http://www.Smacboca.Com/e-matrix-sublative-rejuvenation.Html other options include fractional lasers or subscision. Read more...
Lasers and Subcision. In my hands the best way to get rid of acne scars is with a combination of lasers and a procedure called subcision to release the scar bands. Read more...

Hello sir I have these breakouts that look like pimples on my shoulders chest and upper arm. They appear suddenly and leave scars each time. There is no itchiness or any other type of irritation. They just randomly appear and go away?

See a dermatologist. Probably acne. Various treatments. Meanwhile you can try Benzoyl Peroxide 5% or 2%. Keep off colored fabrics as it will bleach out colors. Usually used at bedtime, used with white towels, white sleep wear. Read more...
Pimples on shoulders. Not enough info for example are you 15 or 50 or 75. If 15 or so would see if these are related to you menses and welcome to womanhood. They will get better as you get older. Read more...