Eliminate a big part of the Root Cause: Stop eating refined sugars, grains, milk and dairy products.
Recently, studies have underscored the role of diet in the formation of acne, especially high glycemic index food in combination with milk protein consumption. Simply put, the endocrinological changes that take place during puberty make us more susceptible to acne and the hormones in milk in combination with high glycemic index foods amplify these changes. From :
“The influence of diet on the induction and aggravation of acne has been a matter of intense debate over the last few years. The pioneering observation by Cordain et al. (1), who demonstrated that acne is a disease of Western civilization and is absent in populations consuming Palaeolithic diets without refined sugars, grains, milk and dairy products, resulted in a paradigm change.”
“We have to appreciate that milk is a species-specific endocrine signalling system that activates a central signalling node in cellular metabolism for stimulation of growth and cell proliferation…”
“The endocrinological changes in milk signalling are thus comparable to the endocrinology of puberty.”
“Acne should be regarded as a … disease of civilization, like obesity, type 2 diabetes and cancer induced by Western diet.”
So there you have it. Change to a diet free of high glycemic foods, grain, or milk and (assuming you don’t have some underlying medical condition that is causing acne) the acne may clear up if these recent studies are correct.
Heal the existing lesions
Wash your face in the morning and evening with mild soap and warm water. Don’t scrub your skin or wash too hard. And don’t pick or squeeze your pimples; this will only make them worse. 
Use an over-the-counter benzoyl peroxide as a first attempt twice per day, as it is the least expensive of the effective treatments.  Some common benzoyl peroxide acne products include Clearasil, Oxy 5 and Neutrogena, but there are many others. The concentration of peroxide doesn’t seem to matter as far as effectiveness, but the higher concentration products will tend to cause more problems with skin irritation, burning, itching and even swelling, so go with the 2.5% concentration. After a week or two, your skin will develop a tolerance, and you can go to a higher concentration if you desire.
For slightly better (albeit more expensive) results, try a combination therapy of an over-the-counter strength topical retinoid at night and benzoyl peroxide during the day. Topical retinoids help make benzoyl peroxide more effective, but they are chemically unstable in sunlight as well as with peroxide and should only be used at night. Retinoids can also irritate the skin so start with a low dose product such as Green Cream – Level 3, for example. 
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Less effective treatments include salicylic acid and resorcinol, among others. However, a mixture of benzoyl peroxide and salicylic acid may produce better results than benzoyl peroxide by itself, but only initially.  This can be accomplished by using salicylic acid cleansing pads followed by application of a benzoyl peroxide cream. You don’t want to go wild, though, mixing ingredients yourself and smearing it on your face, or you could irritate your skin.
There is no quick fix for acne available, and no improvement may be seen for six weeks or even longer (8 – 12 weeks) especially if you continue to eat a high-glycemic load diet and consume milk products. The goal is to prevent new lesions; the current lesions must heal by themselves. Be aware that lack of compliance with the treatment is the greatest cause of treatment failure. 
You may want to take the nutritional supplement lactoferrin twice a day as this has been associated with a reduced number of lesions in one uncontrolled study. 
Expensive acne treatment “systems” with a cleanser, exfoliator, toner, repairing and revitalizing solutions, etc., typically found on the internet, look attractive to acne sufferers, but usually don’t work any faster than benzoyl peroxide and salicylic acid. You might do just as well with Zest soap and some pads and cream. The rational behind the expensive treatments is not that they work faster or are more effective but that they are formulated to be less likely to dry out your skin.
Is benzoyl peroxide safe? Benzoyl peroxide has been used to treat acne for over 40 years and there have been no reports of adverse affects that could be related to skin cancer. Two controlled studies on humans have been done, and no relationship was found between benzoyl peroxide and skin cancer. In 16 studies of rodents with benzoyl peroxide applied to the skin, no correlation was found. In one case, benzoyl peroxide in acetone was applied to the skin of mice for 1 year and an increase in skin cancer was reported, but the control group of the study was too small to determine if the results were significant or just due to random chance. In six other similar studies, no increase was found. 
Historically, treatments for acne containing sulfur have been used for thousands of years, and they still are, but there are a couple of side effects: a bad smell and skin discoloration.
Sunlight is known to improve acne, presumably due to the antibacterial effect of ultraviolet light, but it can’t be used as a long-term treatment because of the likelihood of skin damage. 
Tea tree oil in the form of a 5% gel was found in one study to be roughly equivalent to benzoyl peroxide in treating acne. It was somewhat slower to act but skin discomfort was reported far less frequently than for peroxide. 
For more advanced acne, it’s best to seek treatment from a dermatologist to avoid scarring or other permanent damage. There are a variety of prescription treatments, including antibiotics, that are more effective than over-the-counter drugs for more entrenched acne but which require a professional to administer because of possible side effects or the potential for abuse.  And ask your doctor for a referral to see a dietitian.
Once your acne clears up, you will need to continue your diet and your once per day washing and probably dilute peroxide application to prevent new lesions from forming. If you want, you can save some money by diluting your peroxide product by 50% with water.
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 What Can I Do About Pimples?, Patient Handout, American Academy of Family Physicians, 2000 Jan 15; 61(2):366.
 S. Feldman, R. Careccia, K. Barham, & J. Hancox, Diagnosis and Treatment of Acne, American Academy of Family Physicians, 2004 May 1; 69(9):2123-2130.
 M. Tsoukas, E. Stokar, Acne Vulgaris, New Innovations in Topical Therapies, Advance for Nurse Practitioners and Physician Assistants, November 18, 2011
 Seidler E, Kimball, M. , “Meta-analysis comparing efficacy of benzoyl peroxide, clindamycin, benzoyl peroxide with salicylic acid, and combination benzoyl peroxide/clindamycin in acne” ,Journal of American Academy of Dermatology, 20 May 2010
 E. Mueller, et al, Efficacy and tolerability of oral lactoferrin supplementation in mild to moderate acne vulgaris: an exploratory study, Informa healthcare, April 2011, Vol. 27, No. 4 , Pages 793-797
 Kraus A, Munro I, Orr J, Binder R, LeBoeuf R, Williams G.”Benzoyl peroxide: an integrated human safety assessment for carcinogenicity“, American Journal of Clinical Dermatology, 2001;2(3):135-41.
 World Health Organization Health effects of UV radiation
 K. Martin, E. Ernst, Herbal medicines for treatment of bacterial infections: a review of controlled clinical trials, Journal of Antimicrobial Chemotherapy Volume 51, Issue 2
 B. Melnik, A, Diet in Acne: Further Evidence for the Role of Nutrient Signalling in Acne Pathogenesis, Acta Derm Venereol 2012; 92