Smegma is a substance that forms in the sex organs of mammals. It is made of epithelial cells, skin cells, and moisture. It is found around the foreskin of the penis in males, or in the folds of skin around the vulva in females. In males, the smegma acts like a lubricant which makes sexual intercourse easier. It can be white through to yellow in colour. Smegma does not cause any harm, and normal washing will keep it under control; in fact too much washing may cause other problems.