Humans have used galls for various purposes for a long time.

Humans have used galls for various purposes for a long time. Aside from their bizarre appearance, galls also concentrate plant resources and chemical compounds in ways that benefit not only the gall-inducing organisms but also humans. For example, oak galls induced by wasps contain high concentration of tannic acid, which has been used in the production of inks (famously iron gall ink), textile dyes, and leather tanning. Galls have also been used medicinally since ancient times because they were believed to have healing properties, and research suggests there are indeed chemical compounds underlying some of those traditional uses.

(need more research...)