Benzoyl peroxide works by reducing the amount of acne-causing bacteria. It is antimicrobial. It is available in several different concentrations. It also works by drying out the skin and causing it to peel. There are many concerns about benzoyl peroxide as an acne treatment. The FDA has changed the way it views this ingredient over the years. In the 1980s it was seen as completely safe to use and classified as a category 1 ingredient. In the 1990s they changed it to a safety is unknown medicine (category 3) after animal studies linked benzoyl peroxide to tumor growth. In 2010 they renamed it a category 1 medicine after more studies. All products must now have warning stating that it should be used with sunscreen as benzoyl peroxide was found to decrease the skin’s tolerance to UV radiation.
In 2014 the FDA put out a warning for certain over-the counter topical acne products saying the “Can cause rare but serious and potentially life-threatening allergic reactions of severe irritation.” They noted that “Consumers should stop using their topical acne product and seek emergency medical attention immediately if they experience hypersensitivity reactions such as throat tightness; difficulty breathing; feeling faint; or swelling of the eyes, face, lips, or tongue. Consumers should also stop using the product if they develop hives or itching.” 
They said that they could not determine if the serious hypersensitivity reactions were triggered by the acne products’ active ingredients, benzoyl peroxide or salicylic acid, the inactive ingredients, or by a combination of both.
They further stated that “The OTC topical acne products of concern are marketed under various brand names such as Proactiv, Neutrogena, MaxClarity, Oxy, Ambi, Aveeno, Clean & Clear, and as store brands. They are available as gels, lotions, face washes, solutions, cleansing pads, toners, face scrubs, and other products.” 
Topical Retinoids are creams, lotions and gels containing derivatives of vitamin A. The different topical retinoids on the market include: retinol, tretinoin, adapalene, tazarotene, alitretinoin, and bexarotene. All of these treatments work in much the same way and have similar methods of treating acne. They can however all irritate the skin.
Topical antibiotics work by killing the bacteria on the skin. However, the bacteria may not be affected at all by the antibiotics. Also, acne bacteria is often resistant to antibiotic medicines or become resistant to the antibiotics over time. In fact, in 2016, with antibiotic resistance reaching the status of global public health crisis, it is not recommended to use topical antibiotics alone for the treatment of acne. Other side effects and risks of topical antibiotics include skin irritation. At times irritation means that you should stop using the product. Contact dermatitis (red, dry, itchy skin) can be due to skin irritation or allergy.
Oral antibiotics are used for moderate to severe acne. The oral antibiotics work by reducing bacteria and inflammation. The oral antibiotics used in the treatment of acne include tetracyclines, such as minocycline and doxycycline. There are many possible side effects caused by oral antibiotics. To begin, the bacteria may build up resistance to the antibiotics. Oral antibiotics may also cause upset stomach and dizziness. These drugs also increase your skin’s sun sensitivity, cause discoloration of developing permanent teeth and the development of a vaginal yeast infection. Children born to women who were pregnant while taking tetracyclines experienced reduced bone growth.
Hormonal / Antiandrogen Therapy
These treatments are option for women with endocrine abnormalities or difficult-to-treat acne. Hormone-based therapies including combined oral contraceptive medications and spironolactone. Contraceptives used to treat acne have higher amounts of estrogen when compared with other birth control pills. Some examples of oral contraceptives used in acne treatement are: Ortho-TriCyclin, Estro-Step, Alesse, and Yasmin. Oral contraceptive side effects include menstrual irregularities, fatigue, headache, mood changes, dizziness, breast tenderness and nausea. Once more, women over the age of 35 and women who smoke should be careful when taking these drugs, as oral contraceptives increase the risk of blood clots. Side effects increase with higher doses.
Oral Retinoids (isotretinoin)
Systemic isotretinoin is used in the treatment of severe acne. However, isotretinoin is associated with multiple adverse effects. It must, therefore, be used with appropriate caution and only in selected patients. Some of the side effects include: Teratogenicity is one of the most serious potential side effects. Fifty percent of pregnancies spontaneously abort. About half of the infants that are born have skeletal or cardiovascular deformities. You should prevent getting pregnant if you are taking isotretinoin. A strict contraception regimen must be followed. Adolescents who have been treated with isotretinoin commonly experience changes in mood including depression. Increased aggression has also been seen in some male patients and the FDA has said that clinicians should warn patients of this side effect. There is also the mucocutaneous side effect. There has been much debate as to whether liver function tests and lipids should be monitored while on therapy. Elevations in these tests occur in almost all patients and rapidly return to pretreatment levels after therapy has been stopped. There are other severe side effects that you should ask your doctor about before taking this medication. 
 Alison Laytoncorresponding, The use of isotretinoin in acne, Dermatoendocrinol. 2009 May-Jun; 1(3): 162–169.