Hydroquinone lightens the skin when applied topically by inhibiting tyrosinase, the enzyme responsible for converting the amino acid tyrosine to the skin pigment melanin, and is used to treat acne-associated postinflammatory hyperpigmentation.[35] By interfering with new production of melanin in the epidermis, hydroquinone leads to less hyperpigmentation as darkened skin cells are naturally shed over time.[35] Improvement in skin hyperpigmentation is typically seen within six months when used twice daily. Hydroquinone is ineffective for hyperpigmentation affecting deeper layers of skin such as the dermis.[35] The use of a sunscreen with SPF 15 or higher in the morning with reapplication every two hours is recommended when using hydroquinone.[35] Its application only to affected areas lowers the risk of lightening the color of normal skin but can lead to a temporary ring of lightened skin around the hyperpigmented area.[35] Hydroquinone is generally well-tolerated; side effects are typically mild (e.g., skin irritation) and occur with use of a higher than the recommended 4% concentration.[35] Most preparations contain the preservative sodium metabisulfite, which has been linked to rare cases of allergic reactions including anaphylaxis and severe asthma exacerbations in susceptible people.[35] In extremely rare cases, repeated improper topical application of high-dose hydroquinone has been associated with an accumulation of homogentisic acid in connective tissues, a condition known as exogenous ochronosis.[35]
Retinoids and retinoid-like drugs. These come as creams, gels and lotions. Retinoid drugs are derived from vitamin A and include tretinoin (Avita, Retin-A, others), adapalene (Differin) and tazarotene (Tazorac, Avage). You apply this medication in the evening, beginning with three times a week, then daily as your skin becomes used to it. It works by preventing plugging of the hair follicles.
Diet. Studies indicate that certain dietary factors, including skim milk and carbohydrate-rich foods — such as bread, bagels and chips — may worsen acne. Chocolate has long been suspected of making acne worse. A small study of 14 men with acne showed that eating chocolate was related to a worsening of symptoms. Further study is needed to examine why this happens and whether people with acne would benefit from following specific dietary restrictions.