Beware – Herbal Skin Remedies Hidden Dangers. 19 Evaluated – their Side Effects and Drug Interactions

(edited from the skintherapyletter.com article: Adverse Reactions to Herbal Therapy in Dermatology)

The use of herbal therapies is on the rise. Because of their convenient availability, some people with chronic skin disorders have attempted to take more control over their health by using herbal remedies along with or instead of conventional treatments. Some people have lost hope; standard treatments have failed to be effective for them. As a result, they seek newer therapies in an attempt to find a “cure” for their problems.

There are many herbal remedies that have scientific merit; they may be of clinical benefit and provide safe, effective and reliable alternatives to conventional medicine. However, herbal products cannot be patented.² They are intended for the self-treatment of a self-diagnosed, self limiting condition.

Although there are numerous herbal therapies that are relevant to the specialty of dermatology, many of these have not been studied in proper randomized, double-blind, placebo controlled trials. Most herbal treatments have evidence that is based on sparse anecdotal reports and word of mouth.

Many of these therapies are considered “natural” and therefore harmless. However, because of the poor regulations that exist in monitoring these drugs, adverse reactions do occur.³ Herbal therapy, therefore, should be avoided in pregnancy, infants and children because of the uncertainty of adverse reactions that could occur. Herbals that are recommended for topical use should not be ingested and vice-versa.

There is little incentive for pharmaceutical companies to investigate or standardize these preparations because it is unlikely patents would be applicable. Because of the assumed safety of natural products, many patients believe these products have “fewer” side-effects. Herbal therapies should be regarded as drugs.

Since drugs have side-effects, such events can be seen with herbals. Drug interactions although infrequent, can also occur with herbal therapies and conventional medications.^4,8 This may be due to altered absorption, distribution and/or excretion.⁶ These effects can increase or decrease the activity of the corresponding drugs and lead to unexpected adverse events or changes in drug efficacy.⁵ Some herbals may be contaminated with toxic substances or the herbal can be toxic alone. Others may have traces of potent topical steroids.⁷ This makes it even more important for an individual to consult with a doctor before taking herbal therapies in combination with other medications.

Herbal Therapies: Side-Effects and Drug Interactions

Evening Primrose Oil (EPO)(Efamol®) ^4,6,8
Used to treat: Acne, atopic dermatitis, psoriasis
Possible side-effects: Gastrointestinal upset, headaches
Drugs that shouldn’t be interacted: Phenothiazines, seizure threshold of phenobarbital, phenytoin

Aloe Vera ^4,6,8,9,16
Used to treat: Abrasions, acne, atopic dermatitis, bites, burns, dermabrasions, frostbite, poison ivy, psoriasis, sunburn
Possible side-effects: Contact dermatitis
Drugs that shouldn’t be interacted: Corticosteroids, potassium

Calendula (Calendula officionalis) ^4,8,9,16
Used to treat: Boils, burns, eczema, herpes simplex or zoster, mouth irritations, ulcers, wounds
Possible side-effects: Allergic reactions, allergic contact dermatitis

Capsaicin (Zostrix®) ^8,9,16
Used to treat: Pityriasis rubra pilaris, post herpetic neuralgia (PHN), itching associated with psoriasis and PUVA
Possible side-effects: Severe burning, intolerability, allergy
Drugs that shouldn’t be interacted: Can cross react with latex, bananas, kiwi, chestnut, avocado

Goldenseal (Hydratis canadensi) ⁴
Used to treat: Boils, hemorrhoids, tinea
Possible Side Effect: Allergic contact dermatitis

Licorice (Glycyrrhiza glabralensis or ura) ^4,6,8,16
Used to treat: Eczema, melasma, “sore mouth”
Possible side-effects: Contraindicated in hypertension, diabetes mellitus, hypokalemia, liver/kidney disorders
Drugs that shouldn’t be interacted: Cyclosporin A (CyA) , digoxin, prednisone, thiazides

Slippery Elm Bark (Ulmas fulva)
Used to treat: Abscesses, boils, herpes simplex, skin irritations, ulcers
Possible side-effects: Dermatitis. CAUTION! Oral form can induce miscarriage in pregnant women.

St. Johns Wort (Hypericum perforatum) ^4,6
Used to treat: Burns, neuralgia, wounds
Possible side-effects: Oral form can cause photosensitivity, erectile dysfunction
Drugs that shouldn’t be interacted: amitriptyline CyA , digoxin, paroxetine, HIV protease inhibitors, oral contraceptives, retrovirals

Thyme (Thymus vulgaris) ⁴
Used to treat: Combined with herbs for alopecia, halitosis, stomatitis
Possible side-effects: Essential oils can be a mucous membrane irritant

Ginkgo (Ginkgo biloba) Garlic, Ginger, Ginseng (Panax ginseng) ^4,8,17
Used to treat: Various conditions
Possible side-effects: Can cause spontaneous bleeding
Drugs that shouldn’t be interacted: Aspirin, NSAIDs, warfarin, heparin

Tea Tree Oil (Melaleuca alternifolia) ^6,8,9
Used to treat: Acne, impetigo, mouth ulcers, psoriasis, tinea (fungal) infections
Possible side-effects: Taken externally- Allergic contact dermatitis, burning, dryness, itching, ⁵ irritation, systemic allergic reactions, can cross react with colophony. Taken internally- TOXIC

Bromelain-Pineapple (Ananas comosus) ¹⁶
Used to treat: Wound healing, postsurgical pain
Possible side-effects: Allergic contact dermatitis, gastrointestinal upset, diarrhea
Drugs that shouldn’t be interacted: Ethyl acrylate

Borage Oil ¹⁵
Used to treat: Atopic dermatitis
Possible side-effects: Potential for hepatotoxicity orally, no toxicity data for topical use.

Yarrow (Achillea millefolium) ¹⁶
Used to treat: Compress for weeping lesions, itchy skin
Possible side-effects: Allergic contact dermatitis

Fenugreek (Trigonella foenum-graecum) ¹⁶
Used to treat: Compress for weeping lesions
Possible side-effects: Taken externally – Skin irritation. Taken internally – Hypoglycemia
Drugs that shouldn’t be interacted: Hypoglycemics

Chamomile (Matricaria recuita L) ^4,6,9,16,18
Used to treat: Atopic dermatitis, candida albicans, gram-positive infections
Possible side-effects: Allergic contact dermatitis, anaphylaxis
Drugs that shouldn’t be interacted: Hypersensitivity cross-reactions to ragweed, Chrysanthemums (Compositae family)

Arnica (A Montana) ^8,9
Possible side-effects: Taken externally – Allergic contact dermatitis. Taken internally – TOXIC

Horse Chestnut seed extract (Aesculus hippocastanum) 6,8
Used to treat: Chronic venous insufficiency (swelling, itching, tenderness)
Possible side-effects: Taken externally – Allergic contact dermatitis. Taken internally – Dizziness, drug induced lupus, GI upset, headache, pruritus

Zemaphyte (Chinese Herbal Therapy) ^6,10-14
Used to treat: Atopic dermatitis
Possible side-effects: Diarrhea, increased liver function tests, reversible dilated cardiomyopathy, reversible acute hepatic illness, fatal hepatic necrosis, symptomatic nephropathy & bladder carcinoma, worsening of atopic dermatitis, acute urticaria
Drugs that shouldn’t be interacted: Methotrexate

It is important for dermatologists and consumers to become aware of these adverse events and interactions in order to better educate their patients and possibly prevent potential and unexpected adverse reactions.⁸