Herbal therapy involves the use of plants or plant parts for medicinal purposes. Although many herbs have been used by various societies for hundreds of years, there is insufficient scientific evidence regarding their safety and effectiveness.

Herbs may be available as fresh, dried or liquid products. Many are available as supplements (e.g., capsule, tablet, powders). Herbs are commonly consumed as an herbal infusion (when an herb is allowed to steep in hot water, similar to tea).

There are a wide variety of herbs used for their purported effects on the body. Some common herbs include chamomile, echinacea, ginkgo biloba, ginseng, goldenseal, peppermint, St. John’s wort and valerian. Potential effects include mild sedation, increased energy and mental alertness, and immune-system stimulation.

Herbs can also produce adverse side effects that range from bothersome (e.g., nausea, abdominal discomfort) to potentially deadly (e.g., hypertension, serious liver damage). Herbs may also interfere with a wide variety of medications, medical conditions, supplements, other herbs, and foods and beverages. For example, many herbs may affect liver functioning, some may increase the risk of bleeding (especially in patients on anticoagulant medications) and others may dangerously intensify effects of certain medications (e.g., sedatives).

Consumers are advised to consult with their physician before taking any type of herb. In general, herbal therapy is not recommended for children, the elderly, and women who are pregnant or breastfeeding. The safety of many herbs for use in these circumstances has not been clearly established.

Herbs are regulated by the U.S. Food and Drug Administration (FDA) as a food, not as a drug. Thus, they do not undergo the rigorous testing and approval process that are required of medications. Manufacturers are responsible for assuring (but are not required to prove) the safety and effectiveness of their products. In addition, the quality and purity of some herbal products has been called into question.

Herbal therapy is the use of plants or plant parts for medicinal or therapeutic purposes. The flowers, fruits, leaves, root, bark, seeds and stems of a plant may be used. Different herbs are associated with a wide range of effects on the body. Some herbs have been used for hundreds of years, although scientific evidence of their efficacy and safety is rarely conclusive. Herbal therapy may also be referred to as herbal medicine, herbal remedy and phytotherapy (“plant therapy”).

Certain conventional medications make use of substances extracted from a plant. The salicylate originally used to make aspirin was extracted from the willow plant, for example. Herbal therapy, on the other hand, typically uses the plant or plant part in its whole form. Many herbs are available as supplements (e.g., capsule, tablet, powders). Some may be added to beverages or foods. Herbs may also be purchased as fresh, dried or liquid products.

Herbs may be prepared in several different ways, including:

• Herbal infusion. Hot or boiling water is poured over the fresh or dried herbs and allowed to steep. The resulting liquid is consumed as a hot or cold beverage. This is the most common method of consuming herbs. An herbal infusion is often called a tea, although this is a misnomer because it does not typically contain leaves from the tea plant.
  
  
• Herbal decoction. Similar to an infusion, except that the herbs are simmered over low heat for a longer period of time. This preparation may be useful for certain roots, barks and berries from which it may require time to extract the desired components.
  
  
• Herbal tincture. Herbs are soaked in a solution of alcohol and water. The alcohol acts as a natural preservative, and the resulting liquid contains a higher concentration of herbal components than is consumed in an infusion or decoction. Tinctures may also be stored for long periods of time in an airtight container. They may be diluted in tea, juice or water before being consumed, although small amounts (e.g., a drop or two) can be placed directly on or under the tongue.
  
  
• Herbal extract. Herbs are soaked in a liquid that removes specific components of the herb. It may be used as a liquid (similar to a tincture) or, after evaporation, in capsules or tablets.

Because herbs are not considered nutrients (and therefore not necessary for the human body to function), there are no deficiency diseases associated with herbs. No recommended daily allowance has been determined for any herb.  

Herbs contain hundreds of chemicals, each of which may have a different action in the body. All plants produce chemical compounds, including primary metabolites (e.g., sugar) and secondary metabolites (e.g., phytochemicals). The primary metabolites are essential to the plant’s growth and development, while the secondary metabolites may have protective or therapeutic functions. When humans consume plant foods, these secondary metabolites are believed to provide protection for the human body as well.

There are a wide variety of herbs used for medicinal or therapeutic purposes. Although many have been used for hundreds of years, their safety and effectiveness have not been established. In many cases, there is a lack of well-designed scientific studies that confirm the purported effects of herbs. In some cases, research has produced mixed results, confirming the effects in some studies, while revealing no effects in other studies.

Some common herbs include:

• Black cohosh. The stems and root of this plant are believed to help alleviate symptoms associated with menopause (e.g., hot flashes) and premenstrual syndrome (PMS). It has also been used for rheumatism (arthritis and muscle pain). Side effects may include headaches and abdominal discomfort.
  
  
• Chamomile. A mild herb associated with a calming effect. It is often used in an herbal infusion (steeped in hot water) and used to promote sleep and aid digestion. It is also commonly used for many ailments, including anxiety, skin infections/inflammation, infantile colic, teething pains and diaper rash.  Side effects are rare, although chamomile may reduce absorption of iron, intensify the effects of sedatives and increase the risk of bleeding if taken with anticoagulants (including aspirin).
  
  
• Echinacea. This plant is purported to stimulate immune system function and is an extremely popular herbal remedy in the United States. Echinacea is often used in an attempt to reduce the severity or duration of colds and the flu, along with other infections. However, studies on its effectiveness have had mixed results. Side effects are rare, but may include gastrointestinal complaints, skin rash, muscle aches or dizziness.
  
  
• Ginkgo biloba. The fruit and seeds of this herb are believed to have three basic functions: improving blood flow throughout the body (especially in the brain), reducing the risk of blood clots and inflammation, and providing antioxidant protection against cellular damage. Ginkgo biloba is believed to aid memory and mental alertness. It has been studied in some cases of dementia, early stage Alzheimer’s disease and leg pain associated with blocked arteries. Side effects may include increased bleeding, headaches, nausea and gastrointestinal complaints.
  
  
• Ginseng. An herb associated with boosting energy and immune-system functioning. It is commonly used to help reduce stress or fatigue. It may also have a laxative effect. Side effects may include nervousness, excitability, insomnia, increased bleeding and hypertension.
  
  
• Goldenseal. The root of this plant may be used to treat wounds, infections, colds and gastrointestinal problems. It is believed to reduce inflammation and may have a mild laxative effect. Hypertension is a possible side effect.
  
  
• Kava. A potent herb associated with stress relief, kava has been used for anxiety and muscle relaxation, tension, sleeplessness and problems with menopause. Side effects may include sleepiness and skin rash. It may exacerbate the effects of sedatives (e.g., alcohol) and may cause severe liver damage.
  
  
• Milk thistle. This plant is believed to reduce the symptoms of depression, certain liver conditions (e.g., cirrhosis, hepatitis) and gall bladder disorders. It is also used to increase breast milk production. Side effects may include stomach upset, diarrhea and bloating.
  
  
• Peppermint. A mild herb used to aid digestion. It is also used in many parts of the world to relieve cough, sore throat, headache, abdominal cramping and gas. Peppermint is popular in herbal infusions.
  
  
• Red clover. The flowering tops of this plant are believed to have an effect on menopausal symptoms, high cholesterol levels, symptoms of prostate enlargement, breast pain associated with menstrual cycles  and osteoporosis. No serious side effects have been reported with the use of red clover.
  
  
• St. John’s wort. A popular herb used in cases of mild to moderate depression, anxiety and sleep disorders. St. John’s wort may interfere with certain medications (e.g., antidepressants, birth control pills, heart/cancer/HIV medications, migraine medications, anticoagulants), making them less effective or increasing their side effects. A variety of side effects are associated with use of St. John’s wort. These include abdominal discomfort, dry mouth, fatigue, dizziness, confusion or anxiousness, skin rash, sexual dysfunction and headaches. This herb may also make a person more susceptible to sunburn (photosensitive) due to an increased sensitivity to sunlight.
  
  
• Saw palmetto. An herb used to alleviate symptoms of urinary inflammation and enlarged prostate. Side effects are not common, but may include abdominal discomfort, tender breasts and reduced sexual desire.
  
  
• Senna. Leaves of this plant are used to make a stimulant laxative. Use of senna is generally believed to be safe, although dependence may develop with long-term use.
  
  
• Valerian. The root and stems of this plant may be used as a sleep aid. It is believed to act as a mild sedative and has a distinctive unpleasant odor. Regular use for a couple weeks is required before effects may occur. It is generally believed to be safe to use for short periods of time (four to six weeks). Side effects may include headaches, dizziness, itchiness and gastrointestinal problems.

The suspected benefits of herbs may vary, depending on the herb involved. However, none of the purported health claims of herbal therapy have been conclusively proven. In many cases, there is insufficient scientific evidence to support the claims. For example, a recent and large study funded by the National Institutes of Health failed to find any link between used of black cohosh and reduction of hot flashes. Another NIH-funded study found no link between echinacea and reduced incidence of cold symptoms.

Herbs are commonly used for their purported medicinal or therapeutic value. While they are not considered drugs, they have certain chemical properties and may affect the human body in certain ways. Side effects of herbal therapy may also vary.

Herbs may also interfere with a wide variety of medications and medical conditions. For example, studies are under way to determine whether or not the use of some herbs prolongs the effects of anesthesia. Herbs may also interact poorly with  supplements, other herbs, and foods and beverages. Consumers are advised to consult with their physician before taking any type of herb.

Taking the herbs kava or valerian while consuming alcohol or taking medications that have a sedative effect may intensify the tranquilizing effects. Eating grapefruit or drinking grapefruit juice while taking herbs may cause more of certain herbs to be absorbed into the body, possibly increasing the risk of adverse side effects. 

Many herbs can interfere with liver functioning (the ability of the liver to break down substances in the body). This can lead to dangerously high concentrations of certain substances being released into the bloodstream. This may be especially problematic for patients with existing liver problems.

Herbs believed to have an effect on blood-clotting abilities (e.g., ginkgo biloba, ginseng) may cause serious side effects for patients with certain blood-related conditions (e.g., hemophilia, diabetes) or medications taken for those conditions. Some herbs (e.g., chamomile) may increase the effects of anticoagulant medications, which can increase the risk of bleeding. Other herbs (e.g., goldenseal) may act in the opposite way, counteracting the effects of these medications and increasing the risk of blood clots.

Certain herbs are known to cause problems when taken for long periods of time. For example, echinacea taken every day for more than two months may damage the liver. This risk is increased in patients taking other medications that may cause liver damage. Long-term use of ginseng may cause insomnia and skin rashes. In many cases, no information about the effects of long-term herbal use is available because studies have not been conducted.

It may be possible to overdose on certain herbs. People may mistakenly believe that more of an herb can double the herb’s effectiveness. However, taking large quantities of any substance, including herbs, can be harmful. Consumers should take no more than the recommended dosage of any medication, including herbs. Taking herbs and medications with similar effects at the same time may lead to an overdose state.

In general, herbal therapy is not recommended for children, elderly people, and women who are pregnant or breastfeeding. The safety of many herbs for use in these circumstances has not been clearly established.

People with certain medical conditions (or on certain medications) may be advised against herbal therapy. This may include patients with cancer, an enlarged prostate gland, epilepsy, glaucoma, heart disease, high blood pressure, immune-system problems, psychiatric problems, Parkinson’s disease and thyroid problems.

People with allergies should also be cautious before taking herbs. Certain plants may contain potential allergens (e.g., black cohosh contains salicylates, which may provoke an allergic reaction in people with allergies to aspirin or other salicylates). An herb may belong to a family of plants the patient is allergic to, and supplements may contain potential allergens not identified on the product label.

Many different herbs may interfere with surgery. They can cause increased bleeding, raise blood pressure, interfere with anesthesia, or adversely impact medications used during or after surgery. Consumers are advised to tell their physician, dentist or other healthcare provider about their use of herbs prior to any surgical procedure.

Herbs that may pose serious health problems include:

• Aristolochic acid. A potential carcinogen that can cause kidney damage.
  
  
• Chaparral. May cause sudden, irreversible liver damage.
  
  
• Comfrey. A possible carcinogen that may cause liver damage. The U.S. Food and Drug Administration (FDA) has recommended the removal of this product from the market.
  
  
• Ephedrine/ephedra sinica/epitonin. A stimulant that can be especially dangerous when mixed with other stimulants (e.g., caffeinated products). Possible effects range from nervousness to seizures, heart attack and death. The FDA has prohibited the sale of supplements that contain ephedra.
  
  
• Lobelia. Particularly dangerous to people with heart disease, it may cause breathing problems, low blood pressure and death.
  
  
• Germander. May cause liver disease and death.
  
  
• Magnolia-stephania preparation. May lead to kidney failure.
  
  
• Willow bark. This herb has chemical components (salicylates) that can have similar effects to aspirin. Potential adverse effects include Reye syndrome (fast-acting and potentially fatal disease in children associated with aspirin use following a viral infection) and possible allergic reactions.
  
  
• Wormwood. May cause neurological effects such as arm or leg numbness, delirium and paralysis.
  
  
• Yohimbe. May result in kidney failure, stomach problems, fatigue, seizures, paralysis and death.

Herbs are regulated by the U.S. Food and Drug Administration (FDA) as foods, not drugs. Thus, they do not have to undergo the same rigorous trials and testing as medications. In most cases, there is a lack of independent and well-designed scientific studies supporting the claims of herbal therapy. 

Herbal manufacturers are not required to prove the safety and effectiveness of their products. In addition, they are not required to report any adverse effects to the FDA. They are required to be truthful and not misleading about any claims made on the product packaging, although no FDA-approved health claims can be made about herbs. All supplements, including herbal supplements, must include a disclaimer that the product claims have not been evaluated by the FDA and that the product is not intended to diagnose, treat, cure or prevent any disease.

The quality and purity of herbal therapy products has been questioned. Herbal supplements may include contaminants (e.g., metals, microorganisms) that may not necessarily be identified on the product label, which could have adverse effects on consumers. In many cases, the specific active ingredient in herbal products is not known. Herbs may contain many different active compounds that contribute toward a potential effect on the body.

In addition, herbal supplements are not currently required to be standardized within the United States. Thus, it is not possible to ensure precise outcomes for every herbal product. Levels of active ingredients in supplements may vary significantly from batch to batch. The amount of active ingredient in a product may also differ, depending on manufacturer, product type and form (e.g., capsule, liquid). Until formal national guidelines can be established, supplements that currently indicate “standardized” on their label do not necessarily indicate product quality.

Likewise, just because an herbal therapy product is labeled as “natural” does not ensure that it is safe or effective. Certain plants may be toxic while others, when taken in large doses or over a long period of time, may have toxic effects. Dose and strength are important factors in determining a product’s safety. Consumers are advised to follow the instructions on the product package and to consult a physician or registered dietitian about use of herbs. 

Herbal supplements carrying the term USP (U.S. Pharmacopeia) have met standards for strength, purity and ability to dissolve that this organization requires. Consumers may want to choose supplements with USP on the label.

Preparing questions in advance can help patients have more meaningful discussions with health professionals regarding their conditions. Patients may wish to ask their doctor or registered dietitian the following questions related to herbal therapy:

1. How can herbal therapy benefit me?
   
   
2. What type of herbs do you recommend for me?
   
   
3. In what form should I take these herbs (e.g., supplements, herbal teas)?
   
   
4. How much of these herbs should I take on a daily or weekly basis?
   
   
5. Should I stop using the herbs when I feel better or after a set amount of time?
   
   
6. For how long is it safe to take these herbs?
   
   
7. What are the possible side effects of these herbs?
   
   
8. What changes in my condition should I report to you?  For what symptoms do I need to seek immediate medical attention?
   
   
9. Will these herbs interfere with any of my current medications or medical conditions I have?
   
   
10. Are there certain herbal product brands that are more reliable (regarding safety and effectiveness) than others? Which do you recommend?