J. Graf, MD

Department of Dermatology, New York University Medical Center, New York, USA



ABSTRACT

Herbs have been used in clinical medicine for thousands of years. However, it is only in recent times that we have been able to employ scientific methods to prove the efficacy of many of these herbs and to give us a better understanding of their mechanisms of action. This article will focus on the use of herbs in various dermatological conditions characterized by inflammation and pruritus. Topical preparations of many of these herbs are more commonplace in Europe. However, their availability is increasing in the US. As this is occurring we are witnessing a growing marriage between alternative and traditional medicines.



Key Words:

herbs, anti-inflammatory, astringent, antipruritic

The process of inflammation involves the release of vasoactive mediators and chemotactic factors such as histamine, leukotrienes, proinflammatory prostaglandins and lymphokines. These substances are responsible for the capillary dilation and increase in permeability, resulting in swollen, inflamed tissues.

Turmeric

Many herbs have demonstrated anti-inflammatory activity. Turmeric (Curcuma longa), the major ingredient of curry powder and prepared mustard, has a long history in both Chinese and Ayurvedic (Indian) medicine as an anti-inflammatory agent. The volatile oil fraction of turmeric has demonstrated potent antiinflammatory activity in a variety of experimental animal models, while curcumin, the yellow pigment of turmeric is even more potent in acute inflammation1. When used orally, curcumin inhibits leukotriene formation, inhibits platelet aggregation and stabilizes neutrophilic lysosomal membranes, thus inhibiting inflammation at the cellular level2. Curcumin is reported to possess greater anti-inflammatory activity than ibuprofen3. At low levels, curcumin is a prostaglandin inhibitor, while at higher levels it stimulates the adrenal glands to secrete cortisone4. Formulation difficulties due to the yellow color of curcumin has made topical use slow in coming. However, recent developments in technology may change that. The standard oral dose of curcumin is 250-400 mg, three times a day.

Licorice root

Licorice root (Glycyrrhiza glabra) has been used for centuries to treat inflammatory and viral diseases. The active part of the root contains glycyrrhizin, (a triterpene saponin), at concentrations ranging from 7-10%. It is converted to glycyrrehetic acid (GA) in the body. This herb has been used extensively in Europe as an anti-inflammatory agent, and in Japan as an antiviral agent with success in treating chronic hepatitis. It has been shown to inhibit the activity of proinflammatory prostaglandins and leuktrienes, and appears to have a cortisone-like effect making it useful as an anti-inflammatory5,6. In one study the effects of topical corticosteroids were significantly enhanced by the addition of 2% GA7. Another study reported that the use of topical ointments containing active isomers of GA exerted anti-inflammatory activity in a number of subacute and chronic dermatoses8. When compared, topical corticosteroids were superior in the treatment of acute atopic dermatitis. However, GA was superior when treating chronic conditions such as contact dermatitis, seborrheic dermatitis, psoriasis and other conditions characterized by inflammation and pruritus8. Although topical preparations are not available in the US, compresses can be prepared by adding 3 gm (1 tsp) of the extract in 150 ml of water. Orally, the dosage depends on the form in which it is taken. In powdered root form, the dose is 1-4 gm daily. In fluid extract form, the dose is 1 tsp before meals and as a solid extract, the dose is 1/2 tsp before meals. Generally speaking, although herbs have far fewer side effects, they do exist and caution must be exercised in patients with hypertension when using oral licorice root. Elevations in blood pressure have been reported. Much smaller doses, or none at all, should be used for patients with cardiac or renal histories.

Bromelain

Bromelain, a mixture of proteolytic enzymes from the stem of the pineapple plant, has demonstrated anti-inflammatory activity in a wide variety of conditions. It appears to inhibit the production of pro-inflammatory prostaglandins, induce production of antiinflammatory Series 1 prostaglandins, and reduce capillary permeability9. Bromelain is quite useful postoperatively as an agent to speed healing and reduce postsurgical pain and swelling.

Willow bark

Willow bark (Salix alba) contains salicin, known for its antipyretic and pain relieving activity since ancient times. Available in many forms, willow bark extract can be found in many topical and oral products primarily in health food stores.

Witch hazel

Witch hazel (Hamamelis virginiana) has been used for centuries by Native North American tribes to soothe inflamed skin. Much of the anti-inflammatory properties of witch hazel extracts can be explained by the presence of astringent tannins, which enhance the soothing effects10. However, it is important to note that commercially available witch hazel extract does not contain tannins because they are lost in the distillation process. Nonetheless, it is still believed to be soothing when applied to inflamed skin.

Herb Dosage Side effects Turmeric, Indian saffron (Curcuma longa) 250-400 mg, 3 times/day None known18 Licorice root (Glycyrrhiza glabra) 1-4 gm daily Elevated blood pressure

30-40gm/day for extended periods can lead to electrolyte imbalances18 Bromelain, Pineapple (Ananas comosus) 80-320 mg, 2-3 times/day for 8-10 days19 Ethyl acrylate, an aromatic component of the juice can produce dermal sensitization

Occasional gastric disturbances or diarrhea19 White willow bark (Salix alba) To make a tea: 1-2 tsp of powdered bark steeped in 1 cup boiling water for 8 hours19 Can cause Reye’s syndrome in children < 16 years with a viral illness 19

Can cause GI irritation when taken internally19 Witch hazel (Hamamelis virginiana) External decoction: 2-3 gm fine cut powdered bark in 150 ml water19 For external use only. If taken internally, GI and hepatic damage can occur18 Chamomile (Matricaria recutita and Chamaemelum nobile) 3 gm whole flower head, 3-4 times/day, between meals19 None known19 Yarrow (Achillea millefolium) External: 100 gm/20 l hot water for sitz bath19 Contact dermatitis18 Oak bark (Quercus alba) 3 gm/day of cut herb. For rinses, compresses and gargles: 20gm/l water19 None known19 Walnut leaf (Juglans regia) 2-3 gm dried leaf/100ml water19 None known19 Fenugreek (Trigonella foenum-graecum) Internal: 6 gm/day

External: 50 gm powdered seed/l hot water for poultice19 Excess dosage may cause hypoglycemia18

Repeated external applications can cause undesirable

skin reactions19

Chamomile

Chamomile refers to two distinct plants. Matricaria recutita is known as German or Hungarian chamomile, and Chamaemelum nobile is known as Roman or English chamomile. Although the plants are not identical, they are used for the same types of conditions. The active constituents of chamomile include the terpenoids (bisabolol, matricin, chamazulene) and flavenoids (apigenin, luteolin)11. Studies have documented the antiinflammatory and soothing effects of creams containing chamomile in patients with various inflammatory dermatoses12. It is often used in a variety of cosmetic products and as soothing compresses.

Yarrow

Yarrow (Achillea millefolium), contains anti-inflammatory ingredients including chamazulene. Known for its antiinflammatory and anti-pruritic activity, it is used externally in the form of compresses and bath additives.

Oak bark

Oak bark (Quercus alba) contains a mixture of tannins including catechins, oligomeric proanthrocyanidins and ellagitannins. Due to their astringent, vasoconstrictive and cooling properties they make excellent soothing compresses.

Aloe Vera

The use of aloe as a medicinal can be traced back to 333 BC, and there are over 180 aloe species identified. It is widely used for the treatment of burns and wounds. The active component is a polysaccharide that forms a protective and soothing coating when applied to the skin. The ability of aloe to accelerate wound healing was demonstrated in a study with patients who had fullface dermabrasion20. Aloe vera was also found to be effective in the treatment of psoriasis21 and it has been used as a biologically active vehicle for certain ingredients.

Calendula

Calendula (Calendula officinalis), derived from the marigold plant, is quite widely used in topical skin and hair preparations as a soothing ingredient. Its anti-inflammatory effects are a result of triterpene flavonoids and saponins22. It has been used topically as an antiseptic agent and applied to poorly healing wounds.

Capsaicin

Capsaicin inhibits substance P, a peptide transmitter involved in pain transmission, cutaneous vasodilation, and the inflammatory process. Capsaicin has also been found to be effective in the treatment of plaque-type psoriasis23,24. It is worth noting that the first few applications of topical capsaicin often result in burning and stinging. These symptoms diminish with continued use. However, in both studies noted, the dropout rate was significant due to these reactions.

Other anti-inflammatory herbs

Walnut leaf (Juglans regia), extracted from the dried leaves of the English walnut, contains ellagitannins, whose astringent properties can be soothing to weeping lesions when used as compresses. There are many other topically applied antiinflammatory herbs that are used mostly in Europe and Asia, such as mallow (Malva sylvestris), wild pansy (Viola tricolor), and fenugreek seeds (Trigonella foenum-graecum) that contain several anti-inflammatory saponins.

Bioflavenoids

The bioflavenoids, including quercetin and hesperidin, inhibit histamine release and mast cell degranulation, and support capillary integrity13,14. Quercetin (found in high levels in onions) inhibits phospholipase A2 and lipoxygenase enzymes. This results in the inhibition of proinflammatory prostaglandins and leukotrienes.

Essential fatty acids

The essential fatty acids are those fatty acids that are not synthesized or are poorly synthesized by humans. Historically, a diet rich in land animal fats results in much higher levels of arachidonic acid with a concomitant increase in proinflammatory prostaglandin synthesis. Conversely, a diet rich in fish will have the opposite effect, increasing anti-inflammatory prostaglandins. Several studies demonstrate marked clinical improvement in atopic patients using dietary supplementation with either eicosapentanoic acid (EPA), or gamma-linoleic acid (GLA)15,16,17. The most effective fatty acids include EPA, docosahexanoic acid (DHA) from fish oils, and GLA from plant oils such as borage, black currant, and evening primrose, since they bypass the desaturation enzyme steps. It generally takes several months of fatty acid supplementation before improvement is noted. There are anecdotal reports about the application of evening primrose oil to chapped, irritated skin, leading to clinical improvement and healing.

Conclusion

As our familiarity with herbal ingredients increases and we employ our known scientific methodology to study them physiologically, our ability to treat patients satisfactorily, with fewer side effects will be enhanced. Many more herbs are being studied for their therapeutic as well as preventative roles in traditional medicine, thus narrowing a gap that has been present for many years.

References