Risk factors for the development of acne, other than genetics, have not been conclusively identified. Possible secondary contributors include hormones, infections, diet and stress. Studies investigating the impact of smoking on the incidence and severity of acne have been inconclusive.[2][37][38] Sunlight and cleanliness are not associated with acne.[14]

Accutane (isotretinoin) has a mixed reputation, but among dermatologists it’s the finisher for patients with severe acne. “If you have an acne patient that doesn’t respond to anything, [Accutane] can really be a game changer,” board-certified dermatologist Adam Friedman tells SELF. Accutane is an oral retinoid, and it has all the same benefits of a topical retinol but is even more effective.
Light therapy is a treatment method that involves delivering certain specific wavelengths of light to an area of skin affected by acne. Both regular and laser light have been used. When regular light is used immediately following the application of a sensitizing substance to the skin such as aminolevulinic acid or methyl aminolevulinate, the treatment is referred to as photodynamic therapy (PDT).[10][129] PDT has the most supporting evidence of all light therapies.[78] Many different types of nonablative lasers (i.e., lasers that do not vaporize the top layer of the skin but rather induce a physiologic response in the skin from the light) have been used to treat acne, including those that use infrared wavelengths of light. Ablative lasers (such as CO2 and fractional types) have also been used to treat active acne and its scars. When ablative lasers are used, the treatment is often referred to as laser resurfacing because, as mentioned previously, the entire upper layers of the skin are vaporized.[140] Ablative lasers are associated with higher rates of adverse effects compared with nonablative lasers, with examples being postinflammatory hyperpigmentation, persistent facial redness, and persistent pain.[8][141][142] Physiologically, certain wavelengths of light, used with or without accompanying topical chemicals, are thought to kill bacteria and decrease the size and activity of the glands that produce sebum.[129] As of 2012, evidence for various light therapies was insufficient to recommend them for routine use.[8] Disadvantages of light therapy can include its cost, the need for multiple visits, time required to complete the procedure(s), and pain associated with some of the treatment modalities.[10] Various light therapies appear to provide a short-term benefit, but data for long-term outcomes, and for outcomes in those with severe acne, are sparse;[76][143] it may have a role for individuals whose acne has been resistant to topical medications.[10] A 2016 meta-analysis was unable to conclude whether light therapies were more beneficial than placebo or no treatment, nor how long potential benefits lasted.[144] Typical side effects include skin peeling, temporary reddening of the skin, swelling, and postinflammatory hyperpigmentation.[10]
Dermabrasion is an effective therapeutic procedure for reducing the appearance of superficial atrophic scars of the boxcar and rolling varieties.[31] Ice-pick scars do not respond well to treatment with dermabrasion due to their depth.[31] The procedure is painful and has many potential side effects such as skin sensitivity to sunlight, redness, and decreased pigmentation of the skin.[31] Dermabrasion has fallen out of favor with the introduction of laser resurfacing.[31] Unlike dermabrasion, there is no evidence that microdermabrasion is an effective treatment for acne.[8]
Salicylic Acid – One of the most common topical ingredients you can find over-the-counter, salicylic acid is generally used to reduce the appearance of acne, by reducing swelling and redness. Also known as a beta-hydroxy acid, it exfoliates your skin4 and unclogs your pores, too, but it is quite strong. You’ll only be able to find this in strengths around 2%, but it can still dry and irritate your skin, especially if yours is sensitive. The safest way to use this ingredient is according to the directions!

Acne appears when a pore in our skin clogs. This clog begins with dead skin cells. Normally, dead skin cells rise to surface of the pore, and the body sheds the cells. When the body starts to make lots of sebum (see-bum), oil that keeps our skin from drying out, the dead skin cells can stick together inside the pore. Instead of rising to the surface, the cells become trapped inside the pore.