Horsetail
OTHER NAME(S): Equisetum arvense, field horsetail, horsetail
Overview
Horsetail is a type of fern called Equisetum arvense. It is available in teas and dietary supplements, which are often taken to increase silicon levels and to help with kidney and bladder problems. Horsetail is also sometimes applied to the skin to help with healing. However, its benefits for any use are not well defined. When taken by mouth, horsetail may cause an upset stomach or an increased need to pee. When applied to the skin, it may cause a rash or swelling. Before using horsetail, make sure to tell your health care provider about any health conditions you have or medicines you are taking.
Uses
What is horsetail used for?
Horsetail (Equisetum arvense) is commonly used for kidney and bladder problems and as a source of silicon. It is also sometimes applied to the skin to improve healing. However, the benefits of horsetail for any use are not well defined.
Note: The FDA has not reviewed horsetail for safety and effectiveness. Learn more about dietary supplements here.
How does horsetail work (mechanism of action)?
Horsetail is a type of fern called Equisetum arvense. It contains large amounts of certain vitamins and minerals, including potassium and silicon. The parts of the plant that grow above the ground, such as the leaves and stems, are used to make teas and dietary supplements.
Dietary supplements that contain horsetail are often used to help with kidney or bladder problems. This comes from the idea that horsetail can work as a diuretic, increasing the amount of urine (pee) you make and removing extra water and sodium from your body. Some small studies suggest that horsetail may increase the amount of urine you make by a small amount. But it is unlikely to work as well as a prescription diuretic, and more research is needed to understand its effects. It is not clear if horsetail is useful for any kidney or bladder problems.
Horsetail products are sometimes marketed as a source of silicon (or silica), an element that is naturally found in many foods. Taking silicon by mouth is thought to help improve the health of the bones, skin, hair, and nails. But there may not be enough silicon in horsetail to increase levels in your body, and it is also not entirely clear how your body uses silicon. Most people get enough silicon from their diets, and the effects of taking more are not well defined.
The leaves and stems from horsetail are also sometimes made into juices and certain types of pastes (poultices) that are applied to the skin to help with healing. However, their benefits for this use are not well defined.
Herbal products, such as horsetail, naturally contain many chemicals. The amounts of each chemical in a specific horsetail product may vary. Some, none, or all of these chemicals may have effects on the body. These effects may change depending on how much of each chemical is found in the product you are using.
How should I store horsetail?
You should store horsetail according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.
Side Effects
What are the most common side effects of horsetail?
The most common side effects of horsetail are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.
- Increased need to pee (when taken by mouth)
- Rash or swelling (when applied to the skin)
- Upset stomach (when taken by mouth)
There may be other side effects of horsetail that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.
What are the serious side effects of horsetail?
While less common, the most serious side effects of horsetail are described below, along with what to do if they happen.
Severe Allergic Reactions. Horsetail may cause allergic reactions, which can be serious. Stop using horsetail and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching or skin rash
- Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
Precautions
Who should not use horsetail?
Allergies to Ingredients. People who are allergic to any of the following should not use horsetail.
- Equisetum arvense
- Horsetail
- Silicon
- Any of the ingredients in the specific product
Your pharmacist can tell you all of the ingredients in the specific horsetail products they stock.
What should I know about horsetail before using it?
Horsetail products that are applied to the skin are usually homemade. Horsetail is also available as a tea and a dietary supplement. It cannot be marketed to treat or cure a disease.
Read and follow the directions on the specific product you are using, or use it as recommended by your health care provider.
Keep horsetail out of the reach of children.
Herbal products, such as horsetail, naturally contain many chemicals. The amount of each chemical in a specific horsetail product can change for many reasons, including the area where the plant was grown, the weather during growth, the time of year when it was harvested, and the way that the plant was processed after it was harvested. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.
Horsetail is available in many forms, including dried and ground powder, liquid extract, tea, or capsule. Each of these forms may contain different amounts of the chemicals that are naturally found in the plant.
The FDA has not tested horsetail products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.
What should I tell my health care provider before using horsetail?
Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if horsetail is right for you.
In particular, make sure that you discuss any of the following.
Current and Past Health Conditions.Tell your health care provider if you have any of the following before taking horsetail by mouth.
- An electrolyte imbalance, including low sodium levels
- Dehydration
- Heart failure
- Kidney or liver problems
- Low-sodium diet
Other Medicines and Supplements.Horsetail may interact with other medicines and supplements. Before taking horsetail, tell your health care provider about any prescription or OTC medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.
Pregnancy. It is not known if or how horsetail could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.
Breastfeeding. It is not known if horsetail passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.
Interactions
Does horsetail interact with foods or drinks?
There are no known interactions between horsetail and foods or drinks.
It is unknown if drinking alcohol will affect horsetail.
Does horsetail interact with medicines (drug interactions)?
Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.
In particular, make sure that you discuss if you are using any of the following before taking horsetail.
- A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
- A medicine for HIV or AIDS
- Lithium, which is a medicine for certain mental health conditions
The interactions between horsetail and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with horsetail is incomplete. Always check with your health care provider before taking horsetail with any medicines.
Dosing
What should I do if I accidentally use too much horsetail?
If you or someone else has used too much horsetail, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.
Read the product label closely and speak with a health care provider about how to take horsetail safely. Do not take double or extra doses, even if you miss a dose.
References
- Canadian Journal of Hospital Pharmacy: “Hyponatremia secondary to decreased oral intake and SIADH and possibly exacerbated by horsetail (Equisetum arvense).”
- European Medicines Agency: “Equiseti herba - herbal medicinal product,” “Final assessment report on Equisetum arvense L., herba.”
- Journal of the International Association of Providers of AIDS Care: “Possible drug-herb interaction between herbal supplement containing horsetail (Equisetum arvense) and antiretroviral drugs.”
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]: “Horsetail.”
- Medical Sciences: “Evaluation of the clinical efficacy of a novel palmitoylethanolamide- Equisetum arvense supplement for the management of chronic pain: findings from a prospective clinical trial.”
- Planta Medica: “Silicon resorption from Equisetum arvense tea – a randomized, three-armed pilot study.”
- Scientific Reports: “Relative absorption of silicon from different formulations of dietary supplements: a pilot randomized, double-blind, crossover post-prandial study.”