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Volume 34, Issue 4, Page 32 (April 2003)
Aloe vera Linne, commonly known as aloe vera, is the most potent of the more than 200 aloe species and one of the most widely used herbal products throughout the world.
The aloe vera plant (“aloe” derived from the Arabic “alloeh,” meaning “bitter and shiny substance,” and “vera” from the Latin word for “truth”) is a member of the lily family and native to North Africa and the Arabian peninsula. It thrives in warm, dry climates, but can survive high temperatures and even humid conditions as long as its roots are not submerged in water.
Through human trade and migration, this dynamic plant became known and widely used to cure burns and wounds throughout ancient civilizations in Persia, Egypt, elsewhere in Africa, Greece, Rome, India, and China. Aloe vera appears in the folklore of Japan, the Philippines, and Hawaii. The Spanish used it and brought it to South America and parts of the Caribbean such as Aruba, Curaçao, and Barbados (from which the alternate nomenclature Aloe barbadensis Miller is derived).
Besides using aloe to treat burns (including sunburns) and wounds, various cultures have applied aloe to abrasions, insect bites, cuts, blisters, and frostbite. Aloe is reputed to have potent antiinflammatory and antimicrobial effects, and the fresh or dehydrated whole aloe leaf is sold for the treatment of radiation injuries, ulcers, burns, eczema, and psoriasis. Other anecdotal indications may include seborrhea, acne, androgenetic alopecia, and shingles (herpes zoster).
Aloe is believed to balance the pH of the skin and is used in hundreds of medicines and over-the-counter (OTC) products such as shampoos, soaps, shaving creams, deodorants, sunscreens, moisturizers, and other skin creams to soothe, heal, and protect the skin.
The gel and juice of the aloe vera plant have been used for widely varied purposes. The yellow juice from the outer margins of the leaf, for example, is the traditional source for a laxative.
However, the Food and Drug Administration issued a statement last year identifying laxative aloe ingredients (aloe extract and aloe flower extract) in OTC drug products as misbranded and not generally safe and effective (Fed. Regist. 67:31125-27, 2002).
From wound healing to antitumor potential. Rich in glucomannans and other polysaccharides, the gel and sap from the inner core of the full leaf confer healing qualities and pose no risk. Aloe is known to lessen the itching and inflammation associated with minor wounds. The gel is also believed to be effective in eliminating the yeasts, fungi, and bacteria that infiltrate and inhabit wounds, and to accelerate collagen production.
Research in recent years has determined that aloe contains three agents with significant antitumor potential: emodin, mannose, and lectin. While the use of aloe vera has not achieved unqualified acceptance from the medical establishment, components of the plant are under serious scientific investigation.
In fact, the medical establishment recognizes the use of aloe vera in treating radiation and stasis ulcers and has acknowledged the antibacterial and antifungal effects of aloe vera components (J. Am. Acad. Dermatol. 18[4, pt. 1]:714-20, 1988). Aloe is also indicated for the treatment of frostbite. The vasoconstrictive effects of thromboxane have been shown to improve with the application of aloe vera cream (Postgrad. Med. 88:67-68, 73-77, 1990; Arch. Otolaryngol. Head Neck Surg. 121:678-80, 1995).
Further, aloe vera is recognized as one of the many herbal products to contain pharmacologically active ingredients with the potential to enhance wound healing (Arch. Facial Plast. Surg. 3:127-32, 2001). Such ingredients include salicylates and a carboxypeptidase that inactivates bradykinin in vitro (J. Am. Acad. Dermatol. 18[4, pt. 1]:714-20, 1988).
Aloe is rarely, if ever, mentioned among the wide array of products composing the dermatologic armamentarium for psoriasis. There is some evidence suggesting its usefulness, however. Researchers performed a double-blind, placebo-controlled examination of aloe vera extract 0.5% in a hydrophilic cream for the treatment of psoriasis vulgaris (Trop. Med. Int. Health 1:505-09, 1996). Psoriatic plaques cleared in only 2 of 30 subjects on placebo, while 25 of 30 patients in the aloe group showed clearing.
Inflammation remains a major indication for aloe products. Research has established the antiinflammatory effects of aloe vera gel extracts, which may also confer inhibitory activity, via cyclooxygenase, on the arachidonic acid pathway (J. Ethnopharmacol. 55:69-75, 1996). Immunomodulatory properties of the gel polysaccharides, particularly the acetylated mannans (now a proprietary compound under several patents), have been reported (J. Ethnopharmacol. 68[1-3]:3-37, 1999).
A few recent studies buttress the long-standing anecdotal evidence in support of aloe in the treatment of wounds. An investigation using rats showed that full-thickness wounds treated with aloe vera exhibited elevated biosynthesis of collagen and its degradation, suggesting that aloe vera affected the wound healing process by enhancing collagen turnover in the wounded tissue (Indian J. Exp. Biol. 36:896-901, 1998). In another study using rats, aloe vera exhibited both antiinflammatory and wound healing activity when applied to second-degree burns (J. Med. Assoc. Thai. 83:417-25, 2000).
Similar effects have been seen in studies with humans. Researchers observed that the partial thickness burn wounds of 27 patients treated with aloe vera gel exhibited early epithelialization and faster healing time than the area treated with petroleum jelly gauze. Some patients reported mild discomfort (J. Med. Assoc. Thai. 78:403-09, 1995).
Aloe emodin has emerged as the focus of much research involving aloe vera's capacity for cancer inhibition. Aloe emodin, a hydroxyanthraquinone naturally present in aloe vera leaves, has been noted for its strong inhibition of Merkel cell carcinoma proliferation, but has been found to be nontoxic to normal cells (Am. J. Dermatopathol. 24:17-22, 2002). The antineuroectodermal tumor activity of aloe emodin has been found in vitro and in vivo and may represent a significant new direction for antitumor drugs, according to some researchers (Cancer Res. 60:2800-04, 2000).
Aloe's anticarcinogenic potential may spring from active constituents found to have immunomodulating activity. These small molecular weight compounds prevent UVB-induced immune suppression in the skin by repairing UVB-induced damages on epidermal Langerhans' cells (Immunopharmacology 37[2-3]:153-62, 1997; Int. J. Immunopharmacol. 21:303-10, 1999).
These substances may also play a role in natural cancer therapy. For patients with advanced solid tumors and for whom no other standard therapies are deemed appropriate, investigators have identified some therapeutic benefits from natural cancer therapy with melatonin plus aloe vera extracts, including disease stabilization and survival. (Nat. Immun. 16:27-33, 1998). Also, a combination of vitamin C and aloe vera gel extract supplementation was found to be effective in reducing the severity of chemical hepatocarcinogenesis in a study using Sprague-Dawley rats (Nutrition 14[11-12]:846-52, 1998).
Following an exhaustive literature search of controlled clinical trials on aloe, some researchers expressed skepticism regarding aloe's far-ranging curative reputation.
Results suggest that topical application of aloe vera may be effective for genital herpes and psoriasis, but its effectiveness in wound healing promotion remains unproved, and its use does not prevent radiation-induced injuries (Br. J. Gen. Pract. 49:823-28, 1999).
Although the use of topical aloe vera products is recognized as safe, with reports of truly adverse reactions extremely rare, there are reports of dermatologic side effects (Br. J. Dermatol. 143:923-29, 2000). Mild discomfort has been linked to aloe use in some patients. Specifically, products containing aloe vera (as well as vitamin E) as the major active ingredient are contraindicated in the immediate weeks after surgery for patients undergoing dermabrasion or chemical peels due to a high incidence of contact dermatitis (Cutis 47:193-96, 1991). Application of aloe gel is not contraindicated in women who are pregnant or lactating, but no standards regarding a maximum treatment period have been established.
Product choices challenge consumers. Known traditionally for its soothing and multifaceted capacity to treat a wide variety of skin lesions, aloe vera's use as an active ingredient has exploded in the lucrative field of cosmetics and cosmeceuticals.
Alpha hydroxy acids and aloe are the natural products and extracts used most often in skin care formulations. Hundreds of such products have flooded the market since the mid-1990s.
Aloe vera is even included in a new protective garment. Quantum Labs Inc. received FDA approval in April 2002 for its SoftSkin aloe vera gel-coated glove with vitamin E.
The broad array of processed and commercially available aloe products is known to contain several ingredients, but little is known regarding the stability of the active ingredients.
Some such products have so little aloe or have a compound that is so diluted or unstable as to render no therapeutic effects. Products that list “aloe vera extract” tend to be more dilute, while those listing “aloe gel” are more likely to be effective. The lack of effective regulation of these products, however, makes purchasing them a significant challenge for consumers.
Of course, the practice of cutting the leaves of the plant and directly applying the gel to the skin is widely and anecdotally reported to be effective in the healing of burns, scars, and rashes. Also, some companies offer products that they claim are 100% pure.
Through special heating and cooling processes intended to extend shelf life while retaining therapeutic properties, Roots Herbal Industries and Exports produces 100% Pure Aloe Vera Gel (100 mL, $9.99) from organically grown, pure, green aloe leaves. Aubrey Organics also provides its 100% Pure and Certified Organic Aloe Vera Gel (4 ounces, $6.75) with a small amount of the company's citrus seed extract preservative (which includes vitamins A, C, and E).
Promising results, clinical questions. The use of aloe vera is being promoted for a seemingly limitless variety of conditions. Often, patients know more than doctors about the alleged benefits. Topical products that contain aloe vera appear to be safe, but there is a dearth of published research establishing efficacy.
Aloe appears to have great potential for a wide range of medical applications. The use of aloe in a plethora of OTC topical products, though, is likely yet another attempt by manufacturers to capitalize on deeply entrenched cultural knowledge and more casual popular awareness regarding the benefits of the aloe plant.
While I think the risk of using such products is low, I would like to see randomized, double-blind, case-control studies to quantify any benefits of aloe as a primary active ingredient. Such work is clearly warranted by current findings, especially when noting the cogent evidence on natural or less dilute forms of the plant.
Clinical effectiveness has not yet been sufficiently defined in spite of some promising results.
Dr. Leslie S. Baumann is director of cosmetic dermatology at the University of Miami. To respond to this column, or to suggest topics for future columns, write to Dr. Baumann at our editorial offices via e-mail at email@example.com.
© 2003 International Medical News Group. Published by Elsevier Inc. All rights reserved.