Aloe Vera Gel - Research
Uses described in pharmacopoeias and in traditional systems of medicine
Aloe Vera Gel is widely used for the external treatment of minor wounds and inflammatory skin disorders (1, 14–17). The gel is used in the treatment of minor skin irritations, including burns, bruises, and abrasions (1, 14, 18). The gel is further used in the cosmetics industry as a hydrating ingredient in liquids, creams, sun lotions, shaving creams, lip balms, healing ointments, and face packs (1).
Aloe Vera Gel has been traditionally used as a natural remedy for burns (18, 19). Aloe Vera Gel has been effectively used in the treatment of first- and second-degree thermal burns and radiation burns. Both thermal and radiation burns healed faster with less necrosis when treated with preparations containing Aloe Vera Gel (18, 19). In most cases the gel must be freshly prepared because of its sensitivity to enzymatic, oxidative, or microbial degradation. Aloe Vera Gel is not approved as an internal medication, and internal administration of the gel has not been shown to exert any consistent therapeutic effect.
Uses described in folk medicine, not supported by experimental or clinical data
The treatment of acne, haemorrhoids, psoriasis, anaemia, glaucoma, petit ulcer, tuberculosis, blindness, seborrhoeic dermatitis, and fungal infections (2, 6, 19).
Pharmacology - Wound healing
Clinical investigations suggest that Aloe Vera Gel preparations accelerate wound healing (14, 18). In vivo studies have demonstrated that Aloe Vera Gel promotes wound healing by directly stimulating the activity of macrophages and fibroblasts (14). Fibroblast activation by Aloe Vera Gel has been reported to increase both collagen and proteoglycan synthesis, thereby promoting tissue repair (14). Some of the active principles appear to be polysaccharides composed of several monosaccharides, predominantly mannose. It has been suggested that mannose 6-phosphate, the principal sugar component of Aloe Vera Gel, may be partly responsible for the wound healing properties of the gel (14). Mannose 6-phosphate can bind to the growth factor receptors on the surface of the fibroblasts and thereby enhance their activity (14, 15).
Furthermore, acemannan, a complex carbohydrate isolated from Aloe leaves, has been shown to accelerate wound healing and reduce radiationinduced skin reactions (20, 21). The mechanism of action of acemannan appears to be twofold. First, acemannan is a potent macrophage-activating agent and therefore may stimulate the release of fibrogenic cytokines (21, 22). Second, growth factors may directly bind to acemannan, promoting their stability and prolonging their stimulation of granulation tissue (20).
The therapeutic effects of Aloe Vera Gel also include prevention of progressive dermal ischaemia caused by burns, frostbite, electrical injury and intraarterial drug abuse. In vivo analysis of these injuries demonstrates that Aloe Vera Gel acts as an inhibitor of thromboxane A2, a mediator of progressive tissue damage (14, 17). Several other mechanisms have been proposed to explain the activity of Aloe Vera Gel, including stimulation of the complement linked to polysaccharides, as well as the hydrating, insulating, and protective properties of the gel (1).
Because many of the active ingredients appear to deteriorate on storage, the use of fresh gel is recommended. Studies of the growth of normal human cells in vitro demonstrated that cell growth and attachment were promoted by exposure to fresh Aloe vera leaves, whereas a stabilized Aloe Vera Gel preparation was shown to be cytotoxic to both normal and tumour cells. The cytotoxic effects of the stabilized gel were thought to be due to the addition of other substances to the gel during processing (23).
The anti-inflammatory activity of Aloe Vera Gel has been revealed by a number of in vitro and in vivo studies (14, 17, 24, 25). Fresh Aloe Vera Gel significantly reduced acute inflammation in rats (carrageenin-induced paw oedema), although no effect on chronic inflammation was observed (25). Aloe Vera Gel appears to exert its anti-inflammatory activity through bradykinase activity (24) and thromboxane B2 and prostaglandin F2 inhibition (18, 26). Furthermore, three plant sterols in Aloe Vera Gel reduced inflammation by up to 37% in croton oil-induced oedema in mice (15). Lupeol, one of the sterol compounds found in Aloe vera, was the most active and reduced inflammation in a dosedependent manner (15). These data suggest that specific plant sterols may also contribute to the anti-inflammatory activity of Aloe Vera Gel.
Aloe Vera Gel has been used for the treatment of radiation burns (27–30). Healing of radiation ulcers was observed in two patients treated with Aloe vera cream (27), although the fresh gel was more effective than the cream (29, 30). Complete healing was observed, after treatment with fresh Aloe Vera Gel, in two patients with radiation burns (30). Twenty-seven patients with partialthickness burns were treated with Aloe Vera Gel in a placebo-controlled study (31). The Aloe Vera Gel-treated lesions healed faster (11.8 days) than the burns treated with petroleum jelly gauze (18.2 days), a difference that is statistically significant (t-test, P < 0.002).
Aloe Vera Gel is contraindicated in cases of known allergy to plants in the Liliaceae.
1. Bruneton J. Pharmacognosy, phytochemistry, medicinal plants. Paris, Lavoisier, 1995.
2. Grindlay D, Reynolds T. The Aloe vera phenomenon: a review of the properties and modern uses of the leaf parenchyma gel. Journal of ethnopharmacology, 1986, 16:117– 151.
14. Davis RH et al. Anti-inflammatory and wound healing of growth substance in Aloe vera. Journal of the American Pediatric Medical Association, 1994, 84:77–81.
15. Davis RH et al. Aloe vera, hydrocortisone, and sterol influence on wound tensile strength and anti-inflammation. Journal of the American Pediatric Medical Association, 1994, 84:614–621.
17. McCauley R. Frostbite-methods to minimize tissue loss. Postgraduate medicine, 1990, 88:67–70.
18. Shelton RM. Aloe vera, its chemical and therapeutic properties. International journal of dermatology, 1991, 30:679–683.
19. Haller JS. A drug for all seasons, medical and pharmacological history of aloe. Bulletin of New York Academy of Medicine, 1990, 66:647–659.
20. Tizard AU et al. Effects of acemannan, a complex carbohydrate, on wound healing in young and aged rats. Wounds, a compendium of clinical research and practice, 1995, 6:201–209.
21. Roberts DB, Travis EL. Acemannan-containing wound dressing gels reduce radiation-induced skin reactions in C3H mice. International journal of radiation oncology, biology and physiology, 1995, 15:1047–1052.
22. Karaca K, Sharma JM, Norgren R. Nitric oxide production by chicken macrophages activated by acemannan, a complex carbohydrate extracted from Aloe vera. International journal of immunopharmacology, 1995, 17:183–188.
23. Winters WD, Benavides R, Clouse WJ. Effects of aloe extracts on human normal and tumor cells in vitro. Economic botany, 1981, 35:89–95.
24. Fujita K, Teradaira R. Bradykininase activity of aloe extract. Biochemical pharmacology, 1976, 25:205.
25. Udupa SI, Udupa AL, Kulkarni DR. Anti-inflammatory and wound healing properties of Aloe vera. Fitoterapia, 1994, 65:141–145.
26. Robson MC, Heggers J, Hagstrom WJ. Myth, magic, witchcraft or fact? Aloe vera revisited. Journal of burn care and rehabilitation, 1982, 3:157–162.
27. Collin C. Roentgen dermatitis treated with fresh whole leaf of Aloe vera. American journal of roentgen, 1935, 33:396–397.
28. Wright CS. Aloe vera in the treatment of roentgen ulcers and telangiectasis. Journal of the American Medical Association, 1936, 106:1363–1364.
29. Rattner H. Roentgen ray dermatitis with ulcers. Archives of dermatology and syphilogy, 1936, 33:593–594.
30. Loveman AB. Leaf of Aloe vera in treatment of roentgen ray ulcers. Archives of dermatology and syphilogy, 1937, 36:838–843.
31. Visuthikosol V et al. Effect of Aloe vera gel on healing of burn wounds: a clinical and histological study. Journal of the Medical Association of Thailand, 1995, 78:403–409.
Source: WHO Monographs Vol 1, 1999 -2010