1

Hormonal disease

2

Inflammatory disease

3

Disease of defective follicularization

4

Propionibacterium acnes infection

5

Associated with topical exposure to halogens or oils. 

6

Oral or intravenous intake of medications (e.g. lithium)

7

Related to excess sebum production and oily skin

8

Caused by topical or oral corticosteroids

9

Disease of auto-immunity

10

Toll like receptor 2 up-regulation related acne