Pimples occur due to blockage of oil from oil glands in the skin and it occurs under hormonal influence. Certain factors which may aggravate pimples are stress, oil based occlusive cosmetics and food items like milk and other dairy products. Pimples usually leave behind spots and chances of dark spots increase if you fiddle with them. Treatment of pimples is individualised and it is best to consult a dermatologist for treatment and be regular with it. Regards Dr Vijay Adhe Pune