Salicylic acid
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Salicylic-acid-skeletal.svg/220px-Salicylic-acid-skeletal.svg.png)
Salicylic acid is a chemical substance. It is an acid. It is the base ingredient for a drug called aspirin. It is also used as a food preservative, and to treat diseases of the skin, like acne or warts. It is also used in shampoos to treat dandruff (flaking skin on the head).