What Is Horsetail Tea? Cola de Caballo Benefits & Uses

May 24, 2026

Walk through any mercado in Lima or Cusco and you'll spot bundles of a strange, jointed green stalk tied up with string. Vendors call it cola de caballo, horse's tail, because that is exactly what it looks like. It is horsetail (Equisetum arvense), and Peruvians have brewed it for generations to flush the kidneys and, more recently, to grow stronger hair and nails.

Here is the honest version of what this plant is, what the research actually says, and a few reasons you might want to be careful with it.

A plant older than the dinosaurs

Horsetail is one of the oldest plants still growing on Earth. Its ancestors stood as tall as trees around 350 million years ago, long before the first dinosaurs showed up. The version we drink today is short and weedy, growing along riverbanks and damp Andean fields. What makes it interesting is not its age, though. It is the mineral content.

Horsetail is unusually high in silica, the same compound found in sand and quartz. Most plants do not store much of it, but this one does, which is why the dried stalks feel slightly gritty between your fingers. Silica, and the silicon behind it, plays a role in how the body builds collagen, the protein that holds skin, hair, nails, and connective tissue together. That is the main reason cola de caballo ended up in so many Peruvian hair rinses and skin tonics.

What people drink it for

Two traditions dominate. The first is kidney and urinary support. Across the Peruvian highlands, cola de caballo has long been the tea you reach for when you want to limpiar los rinones, clean the kidneys. It works as a mild diuretic, which simply means it makes you urinate more. One small clinical study from 2014 found that a horsetail extract raised urine output about as much as a common prescription diuretic, without throwing off electrolyte balance over the short test period. That is one study with a few dozen people, so treat it as a promising hint rather than settled fact.

The second tradition is beauty from the inside out. Because of the silica, people drink it or rinse with it hoping for thicker hair and harder nails. The evidence here is thinner. A handful of small studies on silicon supplements suggest a modest benefit for hair strength and bone density, but most of that work used concentrated silicon, not a cup of tea. So the tradition is old and the logic is reasonable, yet nobody should expect a miracle from a teabag.

Other common uses in Peru include rinsing minor scrapes and easing the puffiness that comes with water retention. These lean almost entirely on folk practice.

How Peruvians brew it

The classic method is simple. Pour about 250 ml of just-boiled water over one teabag or a small handful of the dried herb, cover it, and let it steep for 10 minutes. Covering matters, since some of the active compounds escape with the steam. Most people drink one to two cups a day, usually away from meals. For a hair rinse, brew a stronger batch, let it cool, and pour it over clean hair as a final rinse.

A quick word on flavor. Cola de caballo is grassy and a little flat on its own. Many Peruvians brighten it with a squeeze of lemon or blend it with other herbs. If you like a mineral-rich, earthy cup, you will get along with it fine.

The cautions worth taking seriously

This is where horsetail earns a longer warning label than most teas, and we would rather be straight with you about it.

Raw horsetail contains an enzyme called thiaminase that breaks down vitamin B1 (thiamine). Proper drying and brewing with hot water deactivates most of it, which is why traditional preparations always heat the herb. Even so, drinking large amounts for weeks on end could in theory chip away at your B1 levels, so this is not a tea to sip all day, every day, for months.

A few more points. Horsetail acts as a diuretic, so pairing it with prescription water pills can stack the effect and drop your potassium too low. People with kidney disease, heart conditions, or low potassium should check with a doctor first. It also contains trace amounts of nicotine, one reason it is not recommended during pregnancy or breastfeeding, or for young children. Sourcing matters too. A close relative, marsh horsetail (Equisetum palustre), is toxic and can contaminate carelessly harvested batches, so buy from a seller who knows the difference between the two species.

None of this means cola de caballo is dangerous in normal amounts. Generations of Andean families have used it without any trouble. It just means this is a herb to respect, to use in short cycles rather than constantly, and to skip if you fall into one of the groups above. We are not doctors, so when in doubt, ask yours.

Where it fits

If you are drawn to horsetail for kidney and urinary support, it sits naturally alongside the rest of our Kidney & Urinary Health collection, including the blended Rinosan tea that combines several traditional Peruvian kidney herbs. If you are after the mineral angle for hair and skin, mineral-rich nettle (ortiga) tea is another Andean favorite worth trying next to it.

Our horsetail comes from the Peruvian highlands and is packed as plain teabags, the same cola de caballo you would find in a Lima herbolario, just easier to brew at home.