When you take shower, you should wash your hair first. Some people clean the body first, then the hair. In this case, the dirty things and shampoo will leave on your body, especially your back. Also, after physical exercise, you must take bath immediately. If you use hair spray, please use a cloth/towel covering your neck and body. These are my experience. I shared with my friends who had the same problem. The pimple left them.
If you have allergy, you could try QV or SebaMed. Do not use the kid line of QV. My kids and I got rash after using it.