adverse effects of microneedling include post-inflammatory hyperpigmentation and tram track scarring (described as discrete slightly raised scars in a linear distribution similar to a tram track). The latter is thought to be primarily attributable to improper technique by the practitioner, including the use of excessive pressure or inappropriately large needles. Subcision is useful for the treatment of superficial atrophic acne scars and involves the use of a small needle to loosen the fibrotic adhesions that result in the depressed appearance of the scar. Chemical peels can be used to reduce the appearance of acne scars. Mild peels include those using glycolic acid, lactic acid, salicylic acid, Jessner's solution, or a lower concentration (20%) of trichloroacetic acid. These peels only affect the epidermal layer of the skin and can be useful in the treatment of superficial acne scars as well as skin pigmentation changes from inflammatory acne. Higher concentrations of trichloroacetic acid (30–40%) are considered to be medium-strength peels and affect the skin as deep as the papillary dermis. Formulations of trichloroacetic acid concentrated to 50% or more are considered to be deep chemical peels. Medium-strength and deep-strength chemical peels are more effective for deeper atrophic scars but are more likely to cause side effects such as skin pigmentation changes, infection, and small white superficial cysts known as milia. Alternative medicine Researchers are investigating complementary therapies as treatment for people with acne. Low-quality evidence suggests topical application of tea tree oil or bee venom may reduce the total number of skin lesions in those with acne. Tea tree oil appears to be approximately as effective as benzoyl peroxide or salicylic acid but is associated with allergic contact dermatitis. Proposed mechanisms for tea tree oil's anti-acne effects include antibacterial action against C. acnes and anti-inflammatory properties. Numerous other plant-derived therapies have demonstrated positive effects against acne (e.g., basil oil; oligosaccharides from seaweed; however, few well-done studies have examined their use for this purpose. There is a lack of high-quality evidence for the use of acupuncture, herbal medicine, or cupping therapy for acne. Self-care Many over-the-counter treatments in many forms are available, which are often known as cosmeceuticals. Certain types of makeup may be useful to mask acne. In those with oily skin, a water-based product is often preferred. Prognosis Acne usually improves around the age of 20 but may persist into adulthood. Permanent physical scarring may occur. Rare complications from acne or