Horsetail Herb Loose Leaf

Horsetail comes with real cautions, so these are the questions our naturopaths ask in store. They matter more than anything we could tell you about what it's for.

A good fit if

• You're an adult buying it for yourself, and you've read the label of the product you're holding
• You want a short course, not something to take every day
• You're buying a proper tea or extract from a reputable brand, not raw, unheated plant powder
• You're happy to bring your medicine list to us before you start

Check with us first if

• You take prescription medicine of any kind. We didn't find any interaction studies for horsetail, so that question is unanswered rather than cleared.
• You want to take it for more than a few weeks. Traditional European use is for two to four weeks at a time, not as an everyday supplement.
• You're buying raw, unheated horsetail powder. The raw plant contains an enzyme called thiaminase. Heating to 80°C switches it off, standard extracts show no measurable activity, and no thiamine deficiency has been reported in traditional European use.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Pregnancy and breastfeeding. There's no safety data, and European guidance doesn't recommend it.
• Children under 12. It isn't recommended by mouth or on the skin; from 12 up, adult dosing applies.
• Severe heart or kidney disease. Don't take it if you've been told to restrict fluids.
• Problems with how your kidneys handle potassium. Don't take it, because of the risk of high potassium (hyperkalaemia).
• A known sensitivity to horsetail. Case reports include rash, swelling of the hands or face, and one case of cough, breathing difficulty and itching.
• Raw, unheated horsetail powder. It contains a thiaminase enzyme (which breaks down thiamine) that's switched off at 80°C. Standard water or 30% ethanol extracts showed no measurable activity, and no deficiency has been reported in traditional use.
• Long-term use. Silicates have been linked to digestive problems, especially with long-term use.
• How long to take it. Traditional use is documented for two to four weeks; see a doctor if symptoms last more than one week.
• Prescription medicines. We found no interaction study for horsetail, so this is unanswered rather than cleared.