Many herbs have a long history of use and of claimed health benefits. However, some herbs have caused health problems for users. This fact sheet contains points you should consider for your safety if you use, or are thinking about using, herbs for health purposes. It does not discuss whether herbs work for specific diseases and conditions.

What You Should Know:

Are herbal health products and supplements safe because they're natural?

Not necessarily. Don't think that herbal health products and supplements are safer than medicines just because they occur in nature or come from plants. After all, many plants are poisonous! Although herbal products and supplements are advertised as ?natural,? they aren't necessarily natural to the human body.

Unlike prescription and over-the-counter (OTC) medicines, herbal products and supplements don't have to be tested to prove they work well and are safe before they're sold. Also, they may not be pure. They might contain other ingredients, such as plant pollen, that could make you sick. Sometimes they contain drugs that aren't listed on the label, such as steroids or estrogens. Some of these products may even contain toxic (poisonous) substances, such as arsenic, mercury, lead and pesticides.

What types of herbal products and supplements are available?

Hundreds of herbal products and supplements are available. They are advertised to treat just about any symptom. However, trustworthy evidence usually doesn't exist to support these advertising claims.

Some of the most popular herbal products and supplements include chondroitin sulfate, echinacea, ephedra (also called ma huang), garlic, ginkgo biloba, ginseng, glucosamine, kava, melatonin, phytoestrogens (such as black cohosh, dong quai and soy), saw palmetto and St. John's wort.

Do any health problems increase the danger of taking herbal products and supplements?

Yes. Herbal products and supplements may not be safe if you have certain health problems. You also may be at increased risk of problems from these products if you are elderly. Talk to your doctor before taking herbal products if you have any of the following health problems:

Blood clotting problems

Cancer

Diabetes

An enlarged prostate gland

Epilepsy

Glaucoma

Heart disease

High blood pressure

Immune system problems

Psychiatric problems

Parkinson's disease

Liver problems

Stroke

Thyroid problems

If you are going to have surgery, be sure to tell your doctor if you use herbal products. Herbal products can cause problems with surgery, including bleeding and problems with anesthesia. Stop using herbal products at least 2 weeks before surgery, or sooner if your doctor recommends it.

What are possible side effects of herbal products and supplements?

Many herbal products can cause side effects. Download the PDF file below for some examples of problems that may be caused by herbal products.

Can herbal health products or supplements change the way prescription or OTC drugs work?

Yes. Herbal health products or supplements can affect the way the body processes drugs. When this happens, your medicine may not work the way it should. For example, St. John's wort reduces the amount of certain drugs absorbed by the body. This may mean the drugs aren't absorbed at high enough levels to help the conditions for which they are prescribed. This can cause serious problems.

You should be especially cautious about using herbal health products or supplements if you take a drug in one of the following categories:

Drugs to treat depression, anxiety or other psychiatric problems

Anti-seizure drugs

Blood thinners

Blood pressure medicine

Heart medicine

Drugs to treat diabetes

Cancer drugs

If you take any of these drugs, talk to your doctor before taking any type of herbal product or supplement.

Can herbal health products and supplements cause other problems?

Yes. Herbal products and supplements may have other effects that aren't listed in the box above.

About Dietary Supplements

Dietary supplements were defined in a law passed by Congress in 1994. A dietary supplement must meet all of the following conditions:

It is a product (other than tobacco) intended to supplement the diet, which contains one or more of the following: vitamins; minerals; herbs or other botanicals; amino acids; or any combination of the above ingredients.

It is intended to be taken in tablet, capsule, powder, softgel, gelcap, or liquid form.

It is not represented for use as a conventional food or as a sole item of a meal or the diet.

It is labeled as being a dietary supplement.

It's important to know that just because an herbal supplement is labeled "natural" does not mean it is safe or without any harmful effects. For example, the herbs kava and comfrey have been linked to serious liver damage.

Herbal supplements can act in the same way as drugs. Therefore, they can cause medical problems if not used correctly or if taken in large amounts. In some cases, people have experienced negative effects even though they followed the instructions on a supplement label. Women who are pregnant or nursing should be especially cautious about using herbal supplements, since these products can act like drugs. This caution also applies to treating children with herbal supplements.

It is important to consult your health care provider before using an herbal supplement, especially if you are taking any medications (whether prescription or over-the-counter). Some herbal supplements are known to interact with medications in ways that cause health problems. Even if your provider does not know about a particular supplement, he can access the latest medical guidance on its uses, risks, and interactions.