Gingival melanosis (dark spots on the gums) is caused by excess melanin or contact with toxic substances.

The natural colour of the gums is a pale pink, which indicates good health. However, in some people, especially smokers and even passive smokers, there is an increase in gum pigmentation that can darken the brightness of the smile. This is caused by increased melanin secretion and the deposit of toxic substances from tobacco that stimulate benign pigmentation of the gums, known as gingival melanosis. It appears to a greater extent during the first year and usually decreases when smoking is stopped.