Witch hazel contains a rich mix of plant-based compounds, dominated by tannins, with smaller amounts of flavonoids, phenolic acids, and volatile oils. The commercial version you buy at a drugstore is a steam distillate of the bark and twigs of the Hamamelis virginiana plant, mixed with 14% ethanol as a preservative. But what’s in the bottle differs significantly from what’s in the raw plant, because the distillation process strips out most of the tannins that give witch hazel its therapeutic punch.
Tannins: The Primary Active Compounds
Tannins are the star ingredients in witch hazel, and they come in two main types. The first is hamamelitannin, a compound unique to witch hazel and its most characteristic ingredient. The bark contains about 4.77% hamamelitannin by weight, while the leaves contain less than 0.04%. The second type is proanthocyanidins, which are large chain-like molecules built from smaller units called catechins. These polymeric tannins are actually the most abundant compounds in the plant overall, with the building blocks including epicatechin gallate, epigallocatechin, catechin, and epicatechin.
The bark is the tannin powerhouse, containing 8 to 12% total tannins compared to 3 to 10% in the leaves. This is why commercial preparations typically use the bark and twigs rather than the leaves. Gallic acid, another tannin-related compound, makes up about 0.59% of the bark.
These tannins are what give witch hazel its astringent, skin-tightening feel. They work by binding to proteins on the skin’s surface, temporarily tightening tissue and reducing inflammation. The gallate groups attached to many of these tannins are particularly important: each one adds three hydroxyl groups that can neutralize free radicals, making heavily galloylated witch hazel fractions the strongest antioxidants and the most effective at reducing inflammation in skin cells.
Flavonoids and Phenolic Acids
Beyond tannins, witch hazel contains a range of smaller polyphenolic compounds. Among the flavonoids, the extract contains quercetin-3-O-glucoside, isorhamnetin-3-O-glucoside, and naringenin, all in small quantities. Free catechin is present at relatively high levels (about 143 micrograms per gram of extract), along with gallocatechin at about 76 micrograms per gram.
The phenolic acids include ellagic acid as the most abundant at 76 micrograms per gram, followed by 4-hydroxybenzoic acid, vanillic acid, protocatechuic acid, and ferulic acid. These compounds contribute to witch hazel’s antioxidant activity, though they’re present in much smaller amounts than the tannins. Methyl gallate, gallic acid, and a compound called pentagalloylglucose round out the hydrolyzable tannin family in the extract.
Volatile Oils and Aromatic Compounds
When witch hazel is steam-distilled, the process captures a complex mixture of volatile compounds. Researchers have identified roughly 175 individual volatile compounds from the leaves and 168 from the bark, spanning a wide range of chemical families: long-chain hydrocarbons, alcohols, aldehydes, and ketones.
The leaf distillate is rich in monoterpenoids, the lighter aromatic compounds also found in many essential oils. Linalool (the compound that gives lavender its scent) makes up 3.71% of the leaf distillate, with geraniol at 1.75% and terpineol at 1.06%. The bark distillate has a different aromatic profile, dominated by heavier sesquiterpenoids (15.35% of the volatile fraction) including compounds like trans-nerolidol and alpha-eudesmol. The bark distillate also contains notable amounts of phenylpropanoids such as estragole, anethole, and eugenol (the compound responsible for the smell of cloves), plus a significant 1.89% linalool oxide.
These volatile compounds give witch hazel its distinctive herbal smell but contribute relatively little to its skin-care effects compared to the tannins.
What’s in the Drugstore Bottle
The witch hazel you buy at a pharmacy is quite different from a raw bark extract. To meet United States Pharmacopeia (USP) standards, the product must be 86% witch hazel distillate (produced through a closed steam distillation of bark and twigs) and 14% pure ethyl alcohol. That alcohol serves as a preservative and mild antiseptic.
Here’s the critical distinction: the distillation process captures the volatile aromatic compounds and water-soluble molecules but leaves nearly all the tannins behind. The European Medicines Agency has noted that tannins are “almost absent” in distillates. This means the drugstore product contains mostly water, alcohol, and volatile oils, but very little of the tannin content that drives the anti-inflammatory and astringent effects studied in research on witch hazel extracts.
If you want the full tannin content, look for products labeled as witch hazel extract rather than witch hazel distillate. Extracts are made by soaking the bark in a solvent, which pulls out the tannins, flavonoids, and phenolic acids that distillation misses. Some products also come in alcohol-free formulations, replacing the ethanol with other preservatives, which can be less drying on sensitive skin.
How These Ingredients Affect Your Skin
The tannins in witch hazel extract are potent anti-inflammatory agents. In studies on human skin cells (keratinocytes), witch hazel bark extract reduced markers of inflammation and showed anti-acne effects. The mechanism ties back to galloylation: the more gallate groups a tannin carries, the better it scavenges harmful oxygen radicals. These same galloylated fractions were the most effective at protecting DNA from oxidative damage in laboratory tests.
The astringent effect you feel when applying witch hazel, that slight tightening sensation, comes from tannins cross-linking with proteins in the outermost layer of your skin. This temporarily reduces pore size and oil production, which is why witch hazel became a go-to for oily and acne-prone skin. The alcohol in the USP distillate adds to this drying effect, though it can also irritate sensitive skin with repeated use.
The volatile compounds contribute mild antimicrobial activity. Eugenol and linalool both have documented antibacterial properties, though at the concentrations present in witch hazel distillate, their contribution is modest compared to the alcohol content.