Side Effects of Herbal Medicine

Side effects of herbal medicine depend upon the herbs

The side effects of herbal medicine depend upon the herbal remedy, the dosage, and any pharmaceutical medications taken by the patient. Many alternate health treatments, such as adjusting the diet or taking homeopathic remedies, are quite safe. Yet some herbs are tricky and must be taken in the proper amounts for optimal health and wellbeing. Herbs, like any substance ingested in the body, are not without side effects.

Common Side Effects of Herbal Medicine

Any substance ingested into the body can cause side effects. Even food isn't entirely benign, as anyone with lactose intolerance can attest. Herbs are plant-based substances that also act like medicine upon the body. Like any medication, they may have side effects. Many side effects can occur from the interaction of herbal medicines with pharmaceutical medications.

As with all medical information, please speak with your physician or healthcare provider to discuss any specific concerns or questions regarding drug interactions.


Individuals taking St. John's wort to treat depression or anxiety may find their skin becoming more sensitive to the sun. They may burn more easily. Typically, fair-haired and light-skinned Caucasians have the highest incidence of photosensitivity, but this herbal side effect is thankfully rare. Typical cases of photosensitivity occur when people take very high doses of St. John's wort, or take it over a long period of time. If taking St. John's wort, avoid too much sun exposure.

Skin Irritation

Topical herbal antifungal and antibacterial agents such as tea tree oil and lavender may cause rashes or skin irritation, especially if used at full strength. Before using any topical herbal product, try a skin patch test. Place a small amount of the product on the inside of the elbow on one arm only. Wait a few days. If the area remains clear, proceed with using the herbal product.


Everyone's body is different, and some people are more sensitive to herbs than other people. Herbs used to treat anxiety, depression and insomnia may cause excessive daytime sleepiness in certain individuals. These herbs include chamomile, valerian and kava kava, with valerian and kava being the most likely culprits. Avoid driving or using machinery until you're sure of the effects of the herb.

Drug Interactions

Drug interactions are serious side effects of herbal medicine. Many commonly used medications interact with herbs. Herbs may amplify the effect of the medication, as in the case of sedatives, anesthetics, and blood thinners. Others may block the drug from working. This can lead to dangerous consequences.

Interaction with General Anesthesia

One of the most common side effects of herbal medicine is its interaction with pharmaceutical drugs. Of particular danger is the interaction between herbs and anesthetics. Many people undergo general anesthesia for outpatient procedures and diagnostic tests as well as major surgical procedures. Certain herbs, such as kava kava and valerian, may magnify the effect of sedatives and general anesthetics.

Patients must tell their anesthesiologist about all herbs, supplements, vitamins, pharmaceutical medications and alternative remedies they are taking to avoid dangerous drug interactions. The American Society of Anesthesiologists advises patients not to take herbal remedies two weeks prior to receiving any anesthesia because so many herbs can interact with anesthetics as well as cause other complications during surgical procedures. Many doctors also advise against taking dietary supplements prior to surgery for the same reason.

Liver Inflammation

Echinacea, one of the most popular herbs used to boost the immune system and battle colds, may also cause liver inflammation when it interacts with certain pharmaceutical compounds. Echinacea may also prevent certain medications used to treat lupus and other immune-system disorders from working.

Interactions with Anticlotting Medications

Patients taking the commonly prescribed anti-clotting medication Coumadin are advised to avoid all herbal medications unless discussed and approved by their physician. Many herbs interact negatively with Coumadin and cause unsafe reactions.

Herbs that magnify or increase the action of Coumadin include:

Some herbs prevent or block Coumadin from working. These herbs include:

  • Ginseng
  • St. John's wort

Some supplements also interact negatively with Coumadin and related anti-clotting medications. These supplements include Co-Q 10 and green tea extracts.

Be very cautious when taking any supplements with anti-clotting medications, and discuss them with your healthcare provider.

Avoid Dangerous Side Effects

Take steps to avoid dangerous side effects. Always consult with your physician or healthcare provider before taking any herbs, supplements, or alternative remedies. While many modern medical doctors may not be conversant with herbal medicine, they should be able to advise you on potential interactions, or at least access reliable sources to find out for you.

Purchase supplements and herbs from well-known companies. Never try to harvest herbs in the wild. Even the experts are occasionally fooled with disastrous consequences. Harvesting the wrong plant, using the wrong part, or preparing an incorrect dose can be dangerous or fatal. Purchasing herbal supplements from reliable manufacturers also ensures that the doses are consistent, helping you to monitor and measure the success of the herbal medication more easily.

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Side Effects of Herbal Medicine