What is Tannic Acid?

Felicia Dye

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.

Tannic acid is used in wood stain.
Tannic acid is used in wood stain.

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.

Some wines absorb tannins from the oak barrels they are aged in.
Some wines absorb tannins from the oak barrels they are aged in.

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.

After an animal hide has been scraped clean, tannic acids are used to preserve it, resulting in leather.
After an animal hide has been scraped clean, tannic acids are used to preserve it, resulting in leather.

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.

Tannic acid is naturally present in sequoia wood.
Tannic acid is naturally present in sequoia wood.

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.

Tannic acid can be used to treat diarrhea.
Tannic acid can be used to treat diarrhea.

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Discussion Comments


Do herbal teas have tannin acid?


@Mor - I wonder if they ever tried to get tannins from the redwoods back in the days when they still cut them down regularly? I don't think tannic acid is used in the commercial tanning of leather these days, but back then it probably was.

Actually I think these days most tannic acid uses are medical. I know they used to use it to treat burn victims. I've also heard that you can use cold tea bags to stop bleeding in your mouth (after going to the dentist for example) because of the tannic acid in the tea.

It's one of those remedies that's pretty good as a home remedy, but in general there are other things discovered by modern technology that will do better if you get them from the doctor.


One of the things I remember from my visit to the Redwoods in California was the guide explaining that high levels of tannins in the wood of the redwoods is what keeps them from burning in forest fires.

They have forest fires often, sometimes even started deliberately, because the fires burn away all the undergrowth and fallen leaves and leave te redwoods intact (because of the tannins).

If they don't have regular fires, the undergrowth and fallen leaves build up to the point where, when they do have a fire, the fire gets so hot that the tannins aren't enough to stop it and the trees die.


I believe that tannic acid is the reason that some rivers and streams have a dark red or golden color rather than being colorless. They are often called "black" or "red" rivers. It happens when there are certain kinds of trees along the river and, in particular, after it's been raining, but often those rivers are red all the time.

That's possibly how people figured out that you can tan leather with tannic acid, because of the fact that it is often found in certain waters.

I also think that sometimes it's caused low iron levels in groups of people, because they drink from that stream and don't realize that the levels of acid are interfering with their ability to absorb iron.

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