Gum resin is a natural secretion or exudate, often very fragrant, usually obtained by slitting the bark of certain trees. In the wild, the trees secrete the gum-oleoresin to protect themselves from parasite attacks. The use of gum-oleoresin in perfumery means incisions must be made manually on the bark of trees, usually two to three feet off the ground, as is done for myrrh, elemi, or frankincense. In the case of some species, like Balsam of Peru, collectors might climb up to 10 meters above the ground to recover the precious balm.

It might also take the form of a shrub exudate, such as labdanum gum from cistus. Labdanum is a powerfully scented gum-oleoresin that helps the plant to protect itself from moisture loss during the long summer months in southern Spain.