A tannin is an astringent chemical derived from plants. Tannic acid is one type of tannin that has a fairly weak acidity. In some trees, this chemical may act as protection against pests and fires, and it is believed that humans can benefit from the antibacterial, antifungal, and antioxidant properties of the substance. It is also used for industrial purposes, such as leather production and wood staining.
This substance is usually found as a yellow, white, or light brown powder that tends to easily dissolve in water. It generally does not have a smell, but the taste is one that can cause a person to pucker.
Since it will cause constipation in humans, tannic acid can be used to treat diarrhea. It can also be used to reduce the swelling of hemorrhoids and control internal bleeding. Externally, tannin can be added to creams and salves to help combat muscle and joint problems and to help heal wounds. It may also be used for antifungal treatment of the feet, toenails, or fingernails.
People are warned not to consume large amounts of tannic acid, and it should not be consumed on a regular basis. Although it can be helpful in many ways, tannin may also have adverse effects.
One disadvantage is that it is believed to interfere with iron absorption. Iron is a mineral essential to maintaining proper human health, particularly with building strong red blood cells. Tannic acide may also have a negative effect on the digestive process. Use of this substance has been associated with severe liver and kidney damage.
These negative symptoms are associated with using the substance in its pure form or in ways that are not recommended by medical experts. People are not regarded as being at risk of adverse effects with normal usage and consumption. For example, tannins may be absorbed into wine from the oak barrels it is stored in, and are not widely believed to cause many serious side effects for most people.
Tannic acid is naturally present in some types of wood such as oak and sequoia. It is sometimes used to pretreat other types of wood that need to be stained. This substance is also commonly used to tan animal skin to produce leather, and it is often stated that tanning was the first use that humans made of it.