Mastic is a tree. People use the sap (resin) from the trunk to make medicine.
Mastic is used for stomach and intestinal ulcers, breathing problems, muscle aches, and bacterial and fungal infections. It is also used to improve blood circulation.
Some people apply mastic directly to the skin for cuts and as an insect repellent. In dentistry, mastic resin is used as a material for fillings. Chewing the resin releases substances that freshen the breath and tighten the gums.