Do you know how to decipher the ingredients label on your moisturiser? Or whether you should be using retinol? Or what the difference is between AHAs and BHA? Relax and let the Vogue Skincare Alphabet break it down. What is it? BHA, also known as salicylic acid, is beta hydroxy acid - a derivative of aspirin. What is it used for? Salicylic acid has several uses - it's the key active in Pepto-Bismol - but in skincare it is mainly used to fight acne, thanks ...