Salicylic acid is a ‘beta hydroxy acid’ which has the ability to break the structures between the skin cells preventing the pores from clogging with dead skin cells1. This ‘comedolytic’ or peeling effect is beneficial in acne, where clogging of the pores leads to formation of blackheads/whiteheads and spots. Salicylic acid is also known to have anti-inflammatory effects, which is beneficial in acne which is an inflammatory skin disease. Furthermore, salicylic acid decreases the sebum production of the skin. Sebum is the oily, waxy substance which clogs the pores and among other mechanisms leads to formation of spots.
In a small study with people with acne, an exfoliator with 30% salicylic acid applied every two weeks was shown to decrease sebum levels. This effect of salicylic acid was already seen after the second application. The authors suggested this to be caused by its ability to mix with lipids of the skin2.
In a 4 week study of 30 patients with mild-to-moderate acne, a 2% salicylic acid cleanser was reported to reduce the number of blackheads. After two weeks, the effect of salicylic acid was compared with benzoyl peroxide (another anti-acne ingredient), favoring salicylic acid3.
Salicylic acid is lipid-soluble and can therefore mix with the sebum in the hair follicles. People with acne tend to have a higher sebum production leading to oily skin with clogged pores. This is why salicylic acid is thought to be beneficial in acne because salicylic acid leads to decreased sebum production1.
Salicylic acids has also been reported to alleviate the possible darkness of the skin after acne, referred ‘post-inflammatory hyperpigmentation’. A study based on 44 patients with dark skin type (known to be at increased risk of developing post-inflammatory hyperpigmentation), showed to benefit from salicylic acid. After applying a 20% salicylic acid gel combined with 10% mandelic acid during six sessions, the area with hyperpigmentation decreased by 59.8%4.
Because salicylic acid is recommended in low concentrations, the side effects are limited to mild, local irritation in a minority of the acne patients1.
The concentration of an ingredient is important for its efficacy, and therefore products containing the same ingredient may not necessarily have the same effect as in the studies mentioned above.
Updated: July 2017