• BHAs (Salicylic Acid) Are Keratolylic so when applied to the surface break down the cells layer by layer from the outer layer in.

• During trails the AHAs glycolic acid and lactic acid increased the amount of skin cells shed daily (as would be expected with increased cell renewal), after the fourth week reduced shedding initially, then continued to do so throughout the eight week evaluation. These results may provide important clues to mechanism of action or possible long term benefits, and may contribute to its effectiveness against certain disease processes such as dandruff and psoriasis.

• It has been shown in studies that salicylic acid has a higher therapeutic index than lactic acid or glycolic acid.

Therapeutic index= increase in cell renewal divided by irritation caused.

A high therapeutic index is good because it means high cell renewal and low irritation levels.

• Recent research shows that BHAs do not have to be acidic to work. This means that they can be used in products with a pH nearer to the skin's pH of 4.5-5.5 which is not as irritation and is a benefit when used in products which are left on the skin ,e.g. leave on exfoliation boosters, overnight acne treatments. Salicylic acid is also affective at lower pH levels so can also be used in conjunction with AHA in an acidic product e.g. pH 3.4

• Unlike AHAs, Salicylic acid affects the arachidonic cascade and exhibits anti-inflammatory properties, making salicylic acid products less irritating than other hydroxy acids, even though they are more powerful. 

Salicylic acid inhibits the enzyme cyclo-oxygenase (COX2 inhibitor), so reduces the amount of inflammatory prostaglandins produced.

The anti-inflammatory effects of salicylic acid make it a preferred option for clients with acne and rosacea.

• Salicylic Acid also differs from AhAs due to its lipophilic ( oil Soluble) nature which enables it to penetrate sebaceous substance in the hair follicle and exfoliate within. (AHAs being water soluble are not as effective.)

In studies comparing a 2% salicylic acid solution vs. a 8% glycolic Acid solution, the salicylic acid significantly decreased the density of microcomedones, whereas, the glycolic acid solution did not.