All acne is a disorder of what we call the pilosebaceous unit. The pilosebaceous unit consists of the hair shaft, the hair follicle, the sebaceous gland, and the erector pili muscle (which causes hair to stand on end when it contracts).

These units are found everywhere on the body except the palms, soles, top of the feet, and the lower lip. The density of these units is greatest on the face, chest, and upper neck, where acne breakouts are most likely to occur.

https://www.verywellhealth.com/pilosebaceous-unit-1068787#:~...