Have acne in my chest, back and on my shoulders and arms. It causes huge and hard dark spots. I don't know why it's coming. I had this problem? from past 4 years. I don't know if I had any allergies. Duration of acne: >1 year Parts affected from acne: Chest, Back, Shoulders Appearance of acne eruptions: Painful nodules (cysts) Skin type: Oily Typical frequency of acne: All the time Treatment taken so far: None.