The use of natural herbal extracts in topical medications, for common illnesses, has risen dramatically. One reason could be the introduction, about 40 years ago, of the concept of ‘hypoallergens’ for people with poor tolerance to cosmetics. The fallout was the promotion of plant and herbal extracts, as safe products. This caught the popular imagination and even the most skeptical were not left unaffected.

Despite such beliefs, herbal extracts must be seen as a potential source of allergens. Patients often neglect to mention the use of herbal extracts in their medical histories during contact dermatitis evaluations. Dermatologists, therefore, need to be aware of the likely outcomes of the use of herbal extracts in cosmetics.

Allergic contact dermatitis to individual extracts

ALOE: Aloe belongs to a family of mainly African plants of the genus aloe and has been used to treat skin diseases since ancient times. There is, unfortunately, very little research literature on aloe. It is now an ingredient in many cosmetics. Contact dermatitis and urticaria have been reported after application of aloe leaf extract in some people.

ARNICA FLOWERS: These belong to the genus of the Asteracae family. Arnica montana has been used for centuries in cosmetics and to treat sprains, wounds and other injuries. Many cases of contact dermatitis have been reported due to arnica applications. Arnica tincture has been reported to cause bulbous dermatitis after treatment of knee injury, and mild skin trauma. A case of allergic contact dermatitis has been reported from sunflower with cross sensitivity to arnica.

CENTELLA ASIATICA: Centella asiatica is an herbaceous of the Apiaciae family and is known to help heal wounds. Vesicular contact dermatitis on the legs, thighs, face and trunk has been reported from the use of creams containing this ingredient. Contact dermatitis to C asiatica has also been reported in treatment of scars and morphea.

CUCUMBER: This is a widely cultivated plant. A 50 year old cook was reported with hand dermatitis which spread to the face, from handling pickles. Skin tests revealed positive reaction to cucumber.

GINKO BILOBA: This is a deciduous, dioecious native Chinese tree with fan shaped leaves, fleshy yellow seeds and bad odor. Till now, no contact dermatitis cases have been reported from using preparations containing G biloba ingredients. This may be because cosmetics do not contain the plant’s fruit pulp, known to be the only part having allergens. Studies suggest that G biboa may actually be able to reduce allergic contact hypersensitivity reactions.

LAVENDER OIL: Lavender oil is extracted, for its fragrance, from the purplish flowers of lavender, which belongs to a family of aromatic Old World plants of the genus Lavandul. Two contact dermatitis cases have been reported from use of lavender oil. One was due to sleeping on lavender-scented pillows. The other was a case of acute facial dermatitis in a physiotherapist, due to application of lavender scented gel. Patch testing showed positive reaction to lavender. Fragrances and therapy oils containing lavender have been reported to cause contact dermatitis.

PEPPERMINT: Peppermint oil is obtained from the mentha piperita plant, a member of the Lamiaciae family. Its flowers yield a pungent oil. This oil is distilled with steam from the flowering plant, rectified by distillation but the menthol in it is not extracted. Peppermint is used to flavor tooth pastes, candies, gums and mouth sprays for its cooling effect. It contains at least 45% menthol. Contact reactions to peppermint result in burning mouth, recurrent mouth ulcerations and lichenoid reactions in the mouth. Peppermint oil has also been reported to cause contact dermatitis in fragrances and occupational contact dermatitis in food handlers.

SAGE: Sage belongs to the family of plants, known as, salvia and is used as a cooking herb. There are a few reported cases of contact dermatitis associated with sage.

STINGING NETTLE AND CHAMOMILE: These are used commonly in physiotherapy. Nettles have stinging hairs which cause skin irritation on contact. Nettle hairs contain histamine and actylcholine which can cause these skin reactions. Chamomiles are an aromatic perennial herb. Chamomile compresses cause contact dermatitis, aggravate existing eczematous dermatitis, and also causes photo allergic and airborne contact dermatitis. Chmomile is one of them ost common herbs to cause dermatitis.

TEA TREE OIL: This oil is obtained from the leaves of a tea tree called, Melaleuca alternifolia. The oil has been used to treat many diseases including infections and psoriasis. Many cases of contact dermatitis to tree oil have been reported.

No reported cases of contact dermatitis

Mention must also be made of plants and herbs about which there are no reports of contact dermatitis. These include Angelica root, bladderwrack, catnip, comfrey leaf, coriander, green tea, hops, licorice roots and marigold. However, further investigations are needed to confirm their lack of allergenicity, as current testing methods may be flawed.