Gallnut green, also known as nutgalls or oak galls, refers to abnormal growths found on various species of oak trees (Quercus spp.). These formations are induced by certain insects, such as gall wasps or gallflies, which lay their eggs in the bark of oak trees. The tree reacts to the presence of the insect’s egg by forming a tumor-like swelling, which eventually hardens and turns woody, protecting the growing larvae inside.

Gallnuts have been historically used for various purposes. One of their significant applications is in the production of ink and dye. The tannic acid present in gallnuts reacts with iron salts to create a chemical reaction, resulting in a dark, permanent ink. Historically, this ink was widely used for writing and drawing, especially in ancient manuscripts.

1. Tanning leather: The high tannin content in gall nuts makes them useful for tanning leather.
2. Natural dye: They are an essential ingredient in making oak gall ink and can also be combined with iron to produce gray, purple and black shades on textile fibers.Traditional medicine: Gall nuts have been mainly used in traditional medicines including oriental, Chinese Kampo and Ayurveda medicine more than 1000 years.Ink production: Gall nuts were historically used to produce iron gall ink, a type of ink used for writing and art.
3. Pharmaceuticals: infectoria gall nuts are believed to have antiviral, antibacterial, antifungal and antiparasitic properties. They can be used in the treatment of nosocomial infections, periodontitis and tooth decay

These uses highlight the versatility of gall nuts and their value in various industries and applications.