Hi  Acne has genetic predisposition and  is due to hormonal changes in teen agers where there is increased hormone production . seen on face , chest ,back regions . smoking aggravates acne . Lifestyle modification like  cessation of smoking , low calorie and low cholesterol diet with excess of water intake would help.. if severe topical antibiotics also retinoids under supervision will be good .. Drink excess of water to hydrate your body , add more of fruits in your diet, keep face dry, use mild soaps , always use sunscreen when you go out, ,,, consult dermatologist if persist or if any hyperpigmented spots as treatment will be based on skin type and also your skin condition.