What are the tannins in oak bark, and what are they for?

Tannins are a group of plant compounds with pronounced astringent properties. They are what give oak bark decoction its characteristic tart taste and the ‘tightening’ sensation on the skin or mucous membranes.

The mechanism is simple: on contact with the surface of the skin or a mucous membrane, tannins form a thin protective film. This sensation is familiar to anyone who has drunk strong tea or red wine: tannins cause that very ‘dryness’ in the mouth. In the context of external use, this effect is used when an irritated surface needs soothing or a feeling of discomfort needs easing.

Oak bark is considered one of the richest natural sources of tannins among European medicinal plants, which explains its centuries-old presence in herbal tradition for rinses, compresses and baths.

It is important to understand that this is a household plant material, not a medicine. Tannins create an astringent effect on the surface, but this does not mean treating any disease. If there is a specific health problem that requires medical intervention, oak bark will not replace a doctor's consultation.