Warnings about Herbs

Some herbs can indeed have side-effects, and here are a bunch of them.

Like any drug, herbal treatments can have side effects, and this page is an effort to list such warnings. These warnings apply to any use of these herbs, not just in the treatment of psoriasis. Further research into these warnings may or may not be forthcoming (this list is very incomplete), since this information is already widely available. Note that these warnings are presented here not to portray herbs and herbal treatments as bad or deadly, only so that people can make better, more informed choices about their health care. Not knowing about these warnings is just as bad as not knowing about the possible side-effects of mainstream drugs.
See also Quackwatch.


Agrimony may cause sun-sensitivity in some users.


Balm is also known as bee balm, common balm, cure-all, lemon balm, melissa, oswego tea, and/orsweet balm. Do not use if you have thyroid problems.


Do not use bergamot oil when exposing skin to the sunlight.

Burdock Root

Burdock Root is very similar in appearance to Deadly Nightshade — there have been cases of atropine poisoning from commercially available Burdock Root products that had been contaminated with Deadly Nightshade. Burdock Root may irritate the skin.


Cajeput oil can possibly cause skin inflammation. Avoid using on the facial area (especially in infants and small children).


Calendula leaves and the dried flowers can be made into a salve for use on wounds. If you are allergic to plants in the daisy family, calendula may cause an allergic reaction. According to one homeopathy Web siteBroken Link, calendula should not be used for psoriasis.


Cedarwood oil can be used as a topical for warts or in steam inhalation for bronchitis. The essential oil should never be ingested, and pregnant women might want to avoid its use altogether.


Comfrey is used as an astringent, an anodyne, and emollient. Topical formulations of comfrey should only be applied to intact skin.


Dandelion is used as a skin disease remedy (how vague can it get?) and as a diuretic. Avoid use if you have blockage or inflammation of the intestine. Also, dermatitis can occur (rarely, though) in some individuals. Wash dandelion carefully if you pick your own.


Echinacea acts as a stimulant for the immune system. Because psoriasis involves an errant immune system, echinacea might actually worsen the disease. See also the Healthcare Reality CheckBroken Link article on this herb.


Large doses of Goldenseal can be toxic. Signs of overdose include vomiting, breathing difficulty and slowing of the heartbeat. Topical applications may cause skin irritation.

Hawthorn Berries

Hawthorn Berries are often used as a vasodilator. If effective as such, make sure to speak with your doctor prior to use, as it could possibly lead to problems in those people with high or low blood pressure (or other blood circulation problems). Also, this effect can lead to already-inflammed skin looking more deeply red, as the capillaries expand.


Horsetail contains small amounts of nicotine; it could possibly cause nicotine poisoning if large amounts are taken internally. It works as a diuretic also; be sure to drink plenty of liquids if using this (or any other) diuretic. Do not use if you have a thiamin deficiency.


Lavender may cause skin irritation or allergic reactions in some users.


Licorice can pose many health hazards. In doses as low as 100 milligrams daily, swelling of the face and or other parts of the body can occur.

As few as 50 milligrams a day can result in a condition called hypokalemia, an abnormally low blood concentration of potassium. This condition can be life-threatening.

Do not use licorice if you are pregnant or nursing; or if you have high blood pressure, glaucoma, diabetes, kidney disease, or liver disease; if you are using hormonal therapy or digitalis; or if you have had a stroke or heart attack.

Marshmallow Root

Marshmallow Root is often used as a cough suppressant; it contains mucilage. Handling the leaves may irritate the skin.


Nettle can nausea or a feeling of burning on the skin. Do not use while pregnant; in lab tests, nettle has caused uterine contractions in rabbits.


Chinese healers sometimes recommend oregano for itchy skin. Traditionally, oregano has been used to induce menstruation so pregnant women may want to avoid using it.


Pansy (Viola Tricolor) contains salicylic acid (up to 0.3%), which is often used to remove scales in psoriasis, and can enhance the efficacy of other topical treatments. Use of Pansy (as with any salicylic acid product) could possibly lead to dryness or irritation of the skin.

Passion Flower

Passion Flower should be avoided while pregnant. Passion Flower contains compounds which may affect the uterus.

Poplar Bud

Poplar bud’s active ingredient is salicylic acid. This can cause skin irritations. See the warnings for Pansy. Poplar Bud also contains zinc.

Red Clover

Red Clover contains substances that are similar to estrogen. Woman using oral contraceptives, as well as pregnant women, might want to avoid using Red Clover.

Red Rasberry Leaf

Red Raspberry Leaf — Some herbalists recommend avoiding raspberry leaf preparations early in pregnancy. Others advise against its use after the seventh month of pregnancy. Based on these conflicting (and possibly anecdotal) reports, it might be best if the use of red raspberry leaf was avoided altogether during pregnancy.


Sage is used (among other things) as an addition to moisterizers because of its “healing and soothing properties,” but the volatile oil in sage contains a high concentration of a toxic chemical called thujone. Do not ingest purified sage oil — it is toxic. Sage tea can irritate the mouth and lips. Also, because sage may have some estrogen-like effects, pregnant women might want to avoid it.


A 1942 study indicated sarsaparilla might be effective in the treatment of psoriasis. Unfortunately, the study was “open,” and so both the researchers and test subjects knew who was receiving the sarsaparilla and who was receiving the placebo — the test results were likely biased. More recent studies show that sarsaparilla can reduce inflammation by about 25% overno treatment whatsoever, which means it is possible that it can act as a symptom reducer for psoriasis, but much better drugs exist for the reduction of inflammation.

Sarsaparilla contains saponins, which have laxative and diuretic properties. Saponins may intensify the absorption of other medications being taken.

Shepard’s Purse

Shepard’s Purse may induce miscarriage — pregnant women might want to avoid its use.


Thyme is used as an anti-fungal and a skin-soother (a “counterirritant”?). Do not ingest pure thyme oil — it is toxic. Thyme may suppress thyroid function. It could possibly alter a womans menstrual cycle; pregnant women may want to avoid using it. Topical applications of thyme might irritate sensitive skin.

White Oak Bark

White Oak Bark is not recommended for use on damaged skin (such as weeping eczema). Also, “Commission E” monographs note that Oak Bark may reduce or inhibit the absorption of other drugs.


Yarrow may cause skin irritation. Do not use if you are being treated for blood pressure problems or are using anticoagulents. Do not use if pregnant; Yarrow contains trace amounts of thujone, and might possibly cause miscarriage.


The American Pharmaceutical Association Practical Guide to Natural Medicines by Andrea Peirce, published by The Stonesong Press/William Morrow and Co., New York, 1999.

Healing Plants: A Medicinal Guide to North American Plants and Herbs published by The Lyon’s Press, 1998.

The Herb Book by John Lust, published by Bantam Books, 1974.

Home Herbal by Penelope Ody, published by Dorling Kindersley, London, 1995.

The PDR Family Guide to Natural Medicines & Healing Therapies published by Medical Economics Co., Inc., 1999.

Understanding Your Health by Wayne A. Payne Ed.D. and Dale B. Hahn, Ph.D., published by WCB McGraw Hill, 1998.

With the Grain by Ellen Hodgson Brown, published by Carroll and Graf Publishers, Inc., 1990.

Linda M. contributed these warnings. Some additions from Dave W.