Azelaic acid has been shown to be effective for mild to moderate acne when applied topically at a 20% concentration.[66][129] Treatment twice daily for six months is necessary, and is as effective as topical benzoyl peroxide 5%, isotretinoin 0.05%, and erythromycin 2%.[130] Azelaic acid is thought to be an effective acne treatment due to its ability to reduce skin cell accumulation in the follicle, and its antibacterial and anti-inflammatory properties.[66] It has a slight skin-lightening effect due to its ability to inhibit melanin synthesis, and is therefore useful in treating of individuals with acne who are also affected by postinflammatory hyperpigmentation.[1] Azelaic acid may cause skin irritation but is otherwise very safe.[131] It is less effective and more expensive than retinoids.[1]
Considerations: Benzoyl peroxide is able to produce complete clearing of acne only when used in an adequate dosage and within a properly applied benzoyl peroxide regimen. Some dryness, redness, and itchiness is to be expected in the first few weeks of use.6 Scientists call this initial period the "hardening effect" of benzoyl peroxide. About 1-3% of people are allergic to benzoyl peroxide and experience an inflammation of the skin or severe crusting.3This should not be confused with the "hardening effect" of benzoyl peroxide. Benzoyl peroxide, like any other peroxide, can bleach hair and fabric.1
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.