Aloe Veritas

Aloe vera seems to have evolved right alongside the human species. Like man, it thrives in tropical, warm, dry climates. Quite advantageous for our ancestors, as it is a part of many ancient civilizations medicine cabinetsfrom Egypt to Greece, Arabia and Spain. Today, people around the globe consider it part of their medicinal heritage, including China, India, Japan, Russia, the Caribbean, Jamaica and the United States.

"Aloe vera is one of the ingredients that has stood the test of time," said Santiago Rodriguez, Ph.D., CEO, Lorand Laboratories LLC. "There is anecdotal information about use of aloe for thousands of years. Recently, a multitude of peer-reviewed scientific studies give solid support to the anecdotal evidence about the biological activities of Aloe vera both when taken internally or when used orally, making it a very attractive functional ingredient."

Modern consumers dont have to go to a naturopath or medicine man to obtain Aloe vera . In fact, its most likely featured in products found in the small toiletry section of the nearest gas station. Its found everywhere from shaving creams to lotions, cosmetics, soaps, facial and toilet tissues, and sunburn creams. The refrigerated and home cleaning sections also feature Aloe vera with drinks and household cleaners, respectively. And then there are the aloe capsules and juices found in the supplement aisle.

In 2009, SPINS listed Aloe vera first in its five top-selling herbal supplements, and SPINS data from 2010 shows aloe selling $11,695,785 in the natural channel, excluding Whole Foods Market, which was a 6.7-percent increase from 2009.

With good reason, as Aloe vera gel contains many active constituents, including amino acids, vitamins, minerals, sterols, enzymes and polysaccharides. All of the ingredients in Aloe vera  are combined and balanced perfectly in nature to provide a soothing tonic for the body's systems, noted Marina Linsley, marketing director, NP Nutra.

Bill Pine, vice president, Improve USA Inc., agreed and added, Aloe works well with the bodys innate immune system to aid in a defense to protect us from the invasion of what is out there. It is becoming a goal for consumers to try to keep themselves well instead of waiting until they become ill and then going to the doctor. Aloe can assist in this goal.

The plant is also forgiving as it prefers solid sun and can withstand being watered infrequently. Freezing destroys Aloe vera crops only about once every 20 years, which results in a shortage where the bad weather hits. Because Aloe vera is grown in many areas of the globe, a freeze has never eliminated the entire crop, but it has caused rises in global costs.

For modern-day natural product purposes, its important to distinguish the different types of aloe and processing methods. While there are more than 400 known aloe species, Aloe vera , the common name for the species Aloe vera  (L.) Burm f. (or aloe barbadensis) is the primary species used in the majority of products. Aloe arborescens is popular among gardeners, but is rarely used in finished goods

Aloe ferox, also known at aloe capensis, is also not used in natural products too often, but it is approved by many pharmacopeias throughout the world and by FDA as an over-the-counter (OTC) laxative. This aloe type is the primary source of bitter aloes, a strong laxative found in the yellow-brown sap.

Its also important to differentiate between the different parts of the Aloe vera plant used in products, as each component offers different effects in the human body.

The bitter, yellow-brownish, sap-like material found in between the inner leaf and the rind is known as aloe latex and is used primarily in crude drugs. Aloe latex contains anthraquinones, which cause a laxative effect in humans. The anthraquinone aloin is particularly known for its strong laxative effects.

To get to the inner leaf juice (aka aloe gel) without the latex, the plant can be stripped of the outer rind either by hand (known as filleting) or by machine, and then, the latex is rinsed away. The remaining material is then ground or crushed into juice. It used to be a mark of poor filleting if the filleter cut into the leafs parenchyma, which is the inside of the green leaf material, said Mark Blumenthal, founder and executive director of the American Botanical Council (ABC). If you dig too deep, and you get into the latex, which is found in much lower quantities per weight in the Aloe vera /aloe barbadenous than you would find from aloe ferox/aloe capensis for the drug laxative, you will still get some of these anthraquinones in the gel, and therefore, you may have more of a laxative effect than you would normally.

Whole-leaf aloe is obtained by grinding the entire aloe leaf, then removing the rind material and aloe latex via filtration. A good filtration process removes the aloe latex down to 10 ppm or less in orally administered finished products and 50 ppm or less in cosmetic applications. A lot of the industry has gone to whole-leaf Aloe vera gel, Blumenthal noted. Its more efficient and cost effective than manually pressing it out. This whole leaf mash may also have some of the anthraquinones in it.

As ubiquitous as Aloe vera products are, many confuse and combine the properties of the different species of aloe and components of Aloe vera  used. It doesnt help that most pharmacopeias refer to aloe latex simply as aloe or aloe juice. Everyone in the aloe chain, from regulators to manufacturers and consumers, has been mistaken when it comes to aloe preparations.

We have long been aware of the prevalence of adulterated Aloe vera gel commercial products, said Robert A. Sinnott, Ph.D., MNS, co-CEO and chief science officer of Mannatech. Such products have typically been found to contain little (or no) Aloe vera gel, do not have the expected sugar profiles or are contaminated with aloe latex. Aloe latex, the bitter yellow sap from the outer skin of the leaf, contains hydroxyanthracene derivatives, including aloins, and is an OTC laxative drug. Numerous organizations that express concerns about the safety of Aloe vera gel intake often err by including effects of whole-leaf products known to contain aloin.

The International Aloe Science Council (IASC) holds the position that Aloe vera products meant for consumption should have an aloin content of 10 mg/L or less, and companies should be able to provide that information to consumers upon request.

Besides for mixing up the types used, some get further confounded because some manufacturers fairy dust products with Aloe vera so efficacious doses are not present. To combat this issue, IASC established a certification program in the 1980s. The IASC program verifies products contain a string of sugars called acemannan, or beta 1-4 acetylated glucomanan, among other components. Acemannan is naturally occurring in the plant and is measured by IASC using a nuclear magnetic resonance (NMR) method.

All of Improve USA Inc.s aloe has been certified by IASC for purity, according to Pine. We hope most [manufacturers] will use enough aloe in the finished product to actually do the consumer some good. Products that contain a level of aloe that will deliver a benefit will see consumers coming back for more.

According to Rodriguez, Lorand Labs' flagship ingredient BiAloe Aloe vera powder is processed via a proprietary process that ensures  high acemannan content in a soluble form. "Our product has the highest immune-modulatory acemannan content, the highest bioavailable acemannan content and the highest total acemannan content," he said. "The reason we focus so much on the acemannan content of our aloe is because according to the published literature, most of the benefits of including aloe in the diet are due to this very important natural component of Aloe vera." 

Skin Health

If a product has enough acemannan and other healthy aloe components, and contains a minimal amount of aloe latex, it potentially has the power to deliver beneficial effects. Most recognizable are its skin benefits. Aloe vera is calming and moisturizing for the skin, and cumulative evidence supports its use for helping the body to heal small wounds and burns, Linsley said. In fact, a compound present in Aloe vera called acemannan can assist the immune system by boosting the amount of T-lymphocyte cells in the body.

A Brazilian study of 20 women found freeze-dried Aloe vera extract was an effective ingredient for improving skin hydration and suggested it may be used in moisturizing cosmetic formulations and also as a complement in the treatment of dry skin.¹

Expanding beyond dry skin, a 40-study review of dermatology-oriented in vitro and in vivo experiments and clinical trials of Aloe vera  determined oral administration of Aloe vera  in mice is effective on wound healing, can decrease the number and size of papillomas, and reduce the incidence of tumors and leishmania parasitemia by more than 90 percent in the liver, spleen and bone marrow.² The Iranian researchers reported Aloe vera  can be effective for genital herpes, psoriasis, human papilloma virus, seborrheic dermatitis, aphthous stomatitis, xerosis, lichen planus, frostbite, burn, wound healing and inflammation. However, they noted evidence does not support the topical application of Aloe vera  as an effective prevention for radiation-induced injuries and has no sunburn or suntan protection.

Post surgery, aloe can also offer relief. A 2010 study from Iran assessed the effects of Aloe vera  cream in reducing postoperative and post-defecation pain, and its promotion of wound healing after hemorrhoid-removal surgery.³ Researchers found, using a prospective, randomized, double blind, placebo-controlled trial with 49 patients, those in the topical aloe cream group (n=24) had significantly less postoperative pain at 12, 24 and 28 hours, and two weeks after surgery compared to placebo (n=25). Aloe cream reduced the pain after defecation in 24 and 48 hours post surgery (P<0.001). Wound healing at the end of the second postoperative week was significantly greater in the aloe group compared with the placebo group (P<0.001).

Both topical and oral treatments with Aloe vera  were found to have a positive influence on the synthesis of glycosaminoglycans, which maintain and support collagen and elastin, and thereby beneficially modulate wound healing.⁴ A review of clinical trials for burn healing examined Aloe vera s effects in four studies with a total of 371 patients.⁵ The Thai researchers reported the average difference in healing time of the Aloe vera  groups was 8.79 days shorter than those in the control groups (P=0.006).

Aloe vera has also been tested in its ability to help specific skin ailments, such as psoriasis and erythema (reddening of the skin). A randomized, double blind, placebo-controlled Danish trial that included 41 patients reported Aloe vera  gels effects on stable plaque psoriasis was modest and not better than placebo.⁶ However, they noted the high response rate of placebo indicated a possible effect in its own right, which would make the Aloe vera  gel treatment appear less effective. The plant fared better in a German study of 40 volunteers, which found Aloe vera gel (97.5 percent) significantly reduced UV-induced erythema after 48 hours, and was superior to the 1-percent hydrocortisone in the placebo gel.⁷

GI Health

As noted earlier, research has long found aloe ferox produces a laxative effect, and recent research is still examining this outcome. In 2010, an extract of aloe ferox Mill showed improved intestinal motility, increased fecal volume and normalized body weight in constipated rats with a 200-mg/kg dose showing the best efficacy.⁸ These results compared favorably to a standard laxative on various aspects of constipation, according to the researchers at the University of Fort Hare, South Africa.

But Aloe vera also benefits the gastrointestinal (GI) tract with its wound-healing properties, if one considers GI disturbances as wounds. Ingestion of Aloe vera  can be of benefit to the GI system, promoting healthy digestion and bowel function, Linsley said. It encourages the release of digestive enzymes when the stomach is full, and as an alkalizer, it may prevent excessive acid in the digestive process.

 Sinnott said Mannatech has presented numerous posters about Aloe vera gel at scientific meetings, including studies reporting the prebiotic effects of Aloe vera  gel and its digestion by enzymes produced by human intestinal microbiota. We have been investigating the prebiotic properties of our Ambrotose products, which we believe are associated with their effects on GI health, he said.

GI benefits have been reported from non-branded Aloe vera as well. Thai researchers found rats with ulcers that were treated with Aloe vera had lower tumor necrosis factor alpha (TNF-alpha) levels, which signifies less inflammation.⁹ Further, animals in the Aloe vera  grouphad smaller ulcer sizes compared to the ulcer group without treatment.

Moving along to other GI issues, a 2004 study from London concluded oral Aloe vera  taken for four weeks produced clinical remission, improvement and response in nine (30 percent), 11 (37 percent) and 14 (47 percent), respectively, of 30 ulcerative colitis patients given Aloe vera , compared with one (7 percent, P=0.09), one (7 percent, P= ]0.06) and two (14 percent, P<0.05), respectively, of 14 patients taking placebo.¹⁰ Further, the Simple Clinical Colitis Activity Index and histological scores decreased significantly during treatment with Aloe vera  (P=0.01 and P=0.03, respectively), but not with placebo.

While another London study found no evidence Aloe vera benefits patients with irritable bowel syndrome (IBS), the researchers said they could not rule out the possibility that improvement occurred in patients with diarrhea or alternating IBS while taking Aloe vera.¹¹

Aloe vera can also assist the GI tract in absorbing nutrients. A 2010 UC Davis Medical Center, Sacramento, CA, reported aloe gel prepared using the filleting method significantly increased the bioavailability of vitamin C four, six, eight and 24 hours after supplementation, and aloe whole leaf gel increased vitamin Cs bioavailability eight and 24 hours after supplementing compared to baseline and placebo.¹² The researchers also examined both forms effects on plasma vitamin B12 after supplementing and found both aloes significantly increased serum levels at one and two hours compared to baseline and placebo. An earlier study reported both types of aloe improved the absorption of vitamins C and E.¹³

Diabetes

One 2003 study found Aloe vera  can affect both intercellular communication and proliferation of diabetic fibroblasts in vitro, which means it may improve wound healing in those with diabetes,¹⁴ but it can help diabetes patients in more ways than skin health.

While not Aloe vera , aloe excelsa powder produced a dose-dependent reduction in blood glucose levels of diabetic rats.¹⁵

Aloe vera s benefits on diabetes are also shown in scientific studies. For instance, a 2006 Japanese study concluded Aloe vera  gel and phytosterols derived from Aloe vera  gel have a long-term blood glucose level control effect and would be useful for the treatment of type 2 diabetes after the researchers evaluated the anti-hyperglycemic effect of Aloe vera  gel and isolated a number of compounds from the gel, specifically lophenol, 24-methyl-lophenol, 24-ethyl-lophenol, cycloartanol and 24-methylene-cycloartanol.¹⁶ After administration of the five phytosterols for 28 days in mice, fasting blood glucose levels decreased to approximately 64 percent, 28 percent, 47 percent, 51 percent and 55 percent of control levels, respectively.

And, oral administration of 300 mg/kgbw/d of ethanolic extract from Aloe vera  leaf gel to diabetic rats for a period of 21 days significantly restored the alterations in phosphatases and lysosomal hydrolases enzymes activity to near normalcy, comparable with the pharmaceutical drug glibenclamide.¹⁷

Cancer

While few products in the natural arena tout cancer-abating abilities, Aloe vera  has been shown to help reduce tumors and increase lifespan in cancer patients. Back in 1991, Texan researchers noted after 12 weeks, 71 percent of cats that had leukemia and were treated with acemannan were alive and in good health.¹⁸ Normally, the researchers pointed out, 40 percent of cats with feline leukemia are dead within four weeks and 70 percent within eight weeks of the onset of clinical symptoms.

In a 2007 Turkish study, the main lectin present in Aloe vera leaf pulp extract (Aloctin I) decreased the tumor markers serum sialic acid and TNF-alpha levels in mice.¹⁹

Getting out of the cat-and-mouse game, Aloe vera has benefitted human cancer patients as well. A clinical study administered aloe and melatonin to patients with advanced solid tumors for whom no effective standard anticancer therapies are available.²⁰ The study included 50 patients suffering from lung cancer, GI tract tumors, breast cancer or brain glioblastoma, who were treated with melatonin alone (20 mg/d orally in the dark period) or melatonin plus Aloe vera tincture (1 ml twice/d). The percentage of non-progressing patients was significantly higher in the group treated with melatonin plus aloe than in the melatonin-only group (14/24 vs. 7/26, P<0.05). The percentage of one-year survival was significantly higher in patients treated with melatonin plus aloe (9/24 vs. 4/26, P<0.05).

And, aloe emodin, a natural compound from the root and rhizome of Rheum palmatum, inhibited the growth of human cervical cancer cells, HeLa, in a dose-dependent manner at concentrations ranging between 2.5 and 40 micromol/L, increased alkaline phosphatase activity, inhibited expression of proliferating cell nuclear antigen expression, and suppressed the expression of PKCalpha and c-myc, all of which reduce cancer cells.²¹

Like cancer, no cure has been discovered for genital herpes, a simplex virus infection, but it is one of the most common sexually transmitted infections (STIs) worldwide. Thankfully, Aloe vera can play a role in healing outbreak sores. Clinical results from a 2007 study suggested a hydrophilic cream with 0.5-percent Aloe vera  extract is more efficacious than placebo, thus supporting the benefits of Aloe vera  therapy as an alternative, reliable and effective treatment to cure the first episodes of genital herpes in men.²² The group treated with Aloe vera  extract cream had both significantly shorter mean time to healing than the placebo group (4.9 days vs. 12 days; P<0.001) and a higher number of healed patients (20/30 (66.7 percent) vs. 2/30 (6.7 percent); P<0.001).

Regulation and Formulation

With all these health benefits being revealed in a lab setting, Western governments are increasingly allowing Aloe vera to be included in foods and supplements with health claims. In 2008, Aloe vera Group, a Copenhagen, Denmark-based manufacturer of Aloe vera  products, was granted a Natural Products Number (NPN) by Canadian Health Authorities, which allows the company to make label claims that its aloe gel product is effective for treating sunburn, minor burns and cuts, and assists in wound healing. In addition to the Canadian NPN, the company earned approval in European markets, including the Nordic Swan Mark, the Scandinavian eco-label and medical-grade GMP (good manufacturing practice) certification and approval by Danish Health Authorities.

Two years later, in April 2010, an Aloe vera product (Qmatrix® from Aloecorp Inc.) was affirmed GRAS (generally recognized as safe) for use in foods, beverages and supplements in the United States.

Patrick Anderson, western regional sales manager, and David Nelson, international sales manager, Terry Labs, noted cGMPs (current good manufacturing practices), which are FDA required as of last year, have helped the industry by mandating a system that requires vendors to test for identification of products. This helps to eliminate adulteration within the industry, they said.

More governments are OKing aloe, but that doesnt mean this green plant has only smooth sailing in the future. The biggest issue on regulation of aloe may be coming down the pike because of an upcoming report, which Im not sure has been finalized, from the National Toxicology Program (NTP), Blumenthal noted.

NTP, an interagency program with the objective of evaluating substances of possible public health concern, has been conducting a two-year study on an ingredient identified as nondecolorized whole leaf extract of aloe barbadensis Miller In a position paper, IASC said it obtained a sample specimen of the Aloe vera material used in the NTP rodent-feeding studies, and a preliminary chemical analysis showed an aloin content high above IASCs current policy limit of 10 mg/L, according to Devon Powell, executive director of the IASC. Initial reports from the IASC's analysis of the NTP material indicates that the material studied is vastly different than the ingredient sold in products available in the marketplace, in particular in regards to the aloin content, which the NTP has indicated is a likely constituent of concern.

The results of the NTP two-year oral consumption study are expected to be released sometime in 2011, and, according to IASC, the results dont look good for the aloe industry. The IASC has been informed of the high probability the study will conclude that there is clear evidence of carcinogenic activity in test animals, the paper noted. However, IASC urged manufacturers to make sure to inform their consumers of the difference between the ingredient used in the NTP study and those found in their products.

If a substance that is used as an herbal ingredient or dietary supplement gets a negative or less than stellar safety evaluation, it can be problematic for that product with respect to regulation and its position in the market, public-relationship wise, Blumenthal added.

Ingredient suppliers can validate their Aloe vera products to product manufacturers, regulatory agents and consumers by practicing strict processing methods, and ensuring the right kind of aloe is used and in the right dosages.

Sinnott noted Mannatech submitted its Aloe vera gel powders to an independent laboratory for chemical analyses and also conducts product ingredient analyses in house. All of our suppliers are approved through a vendor-qualification process. This includes supplier questionnaires, on-site audits and certificate of analysis (C of A) verification on initial lots. Each subsequent lot is evaluated upon receipt. He added an independent laboratory recently tested Mannatechs Aloe vera gel to make sure it was aloin-free. This laboratory, which was able to detect aloin at levels as low as 0.6 ppm, was not able to detect it in any of our products, he said.

Starting close to the field, Anderson and Nelson said, Stabilization of gels within two hours from harvest to finish raw materials determines the efficacy, quality and integrity of Aloe vera . Terry Labs goes one step further by not adding enzymes to our product, and we also use no heat to concentrate the Aloe vera liquids. We concentrate our liquids using reverse osmosis, which does not require heat.

Processing techniques can also make aloe easier to handle. As Linsley noted, Dehydration is very popular because it provides a very convenient form of Aloe vera with a lot of flexibility for delivery. It's a stable product that is cheap to transport, rehydrates well and is perfect for formulations requiring strict liquid control.

Even with the possible negative press, safe and convenient processing practices will ensure quality Aloe vera products will be available to interested consumers for years to come. The future for Aloe vera is strong because its always been here as a strong medicinal plant, Blumenthal predicted. It has a great deal of cultural receptivity. Its always going to be a part of the fabric of the herbal communitydietary supplements as well as cosmetics and other external products. In addition, specific technologically advanced aloe-base formulations will continue to be used in the natural products industry.

And Linsley duly added, Aloe vera has well and truly earned its position in the marketplace, particularly in personal care products where it is almost ubiquitous because of its well-known benefits for skin and hair. I see it gaining more market share, particularly in functional foods and drinks and supplements, especially as more research emerges.

Its up to product manufacturers to highlight new research to consumers, as well as let them know the differences in the types and processing techniques of Aloe ver , so they can differentiate the products they buy. Still, even with bad press, Aloe vera is sure to continue its popularity. After all, how could all of our ancestors have been wrong?

References are on the next page...

References for "Aloe Veritas"

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2.       Feily A, Namazi MR. Aloe vera in dermatology: a brief review. G Ital Dermatol Venereol. 2009 Feb;144(1):85-91.

3.       Eshghi F., et al. Effects of Aloe vera cream on posthemorrhoidectomy pain and wound healing: results of a randomized, blind, placebo-control study. J Altern Complement Med. 2010 Jun;16(6):647-50.

4.       Chithra P, Sajithlal GB, Chandrakasan G. Influence of Aloe vera on the glycosaminoglycans in the matrix of healing dermal wounds in rats. J Ethnopharmacol. 1998 Jan;59(3):179-86.

5.       Syed TA et al. Management of psoriasis with Aloe vera extract in a hydrophilic cream: a placebo-controlled, double-blind study. Trop Med Int Health. 1996 Aug;1(4):505-9.

6.       Paulsen E, Korsholm L, Brandrup F. A double-blind, placebo-controlled study of a commercial Aloe vera gel in the treatment of slight to moderate psoriasis vulgaris. J Eur Acad Dermatol Venereol. 2005 May;19(3):326-31.

7.       Reuter J, et al. Investigation of the anti-inflammatory potential of Aloe vera gel (97.5%) in the ultraviolet erythema test. Skin Pharmacol Physiol. 2008;21(2):106-10.

8.       Wintola OA, Sunmonu TO, Afolayan AJ. The effect of Aloe ferox Mill. in the treatment of loperamide-induced constipation in Wistar rats. BMC Gastroenterol. 2010 Aug 19;10:95.

9.       Eamlamnam K et al. Effects of Aloe vera and sucralfate on gastric microcirculatory changes, cytokine levels and gastric ulcer healing in rats. World J Gastroenterol. 2006 Apr 7;12(13):2034-9.

10.   Langmead L. Randomized, double-blind, placebo-controlled trial of oral aloe vera gel for active ulcerative colitis. Ailment Pharmacol Ther. 2004;19(7):739-47.

11.   Davis K. Randomised double-blind placebo-controlled trial of aloe vera for irritable bowel syndrome. Int J Clin Pract. 2006;60(9):1080-6.

12.   Yun, J, et al.  A Randomized Placebo-Controlled Crossover trial of Aloe Vera on Bioavailability of Vitamins C and B12 Blood Glucose, and Lipid Profile in Healthy Human Subjects. J Dietary Suppl2010; 7(2):145-153

13.   Vinson JA, Al Kharrat H, Andreoli L. Effect of Aloe vera preparations on the human bioavailability of vitamins C and E. Phytomedicine. 2005 Nov;12(10):760-5.

14.   Abdullah KM et al. Effects of Aloe vera on gap junctional intercellular communication and proliferation of human diabetic and nondiabetic skin fibroblasts. J Altern Complement Med. 2003 Oct;9(5):711-8.

15.   Gundidza M. Anti-diabetic activity of aloe excelsa. Cen Afr J Med. 2005;51(11-12):115-20.

16.   Tanaka M. Identification of five phytosterols from aloe vera gel as anti-diabetic compounds. Biol Pharm Bull. 2006;29(7):1418-22.

17.   Rajasekaran S. Effect of aloe vera lead gel extract on membrane bound phosphatases and lysosmal hydrolases in rats with streptozotocin diabetes. Pharmazie. 2007;62(3):221-5.

18.   Sheets MA. Studies of the effect of acemannan (tradename) on retrosirius infections; clinical stabilization of feline leukemia virus-infected cats. Mol Biother. 1991;3(1):41-5.

19.   Akev N. Tumour preventive effect of Aloe vera leaf pulp lectin (Aloctin I) on Ehrlich ascites tumours in mice. Phytother Res. 2007;21(11):1070-75.

20.   Lissoni P. Biotherapy with the pineal immunomodulating hormone melatonin versus melatonin plus aloe vera in intreatable advanced solid neoplasms. Nat Immun. 1998;16(1):27-33.

21.   Guo JM. Anti-cancer effect of aloe-emodin on cervical cancer cells involves G2/M arrest and induction of differentiation. Acta Pharmacol Sin. 2007;28(12):1991-5.

22.   Syed, T. et al. Management of genital herpes in men with 0.5% Aloe vera extract in a hydrophilic cream: a placebo-controlled double-blind study. J Dermatolog Treat. 2007;8(2):99-102