|Aloe vera plant with flower detail inset|
Aloe vera is a succulent plant species that is found only in cultivation, having no naturally occurring populations, although closely related aloes do occur in northern Africa. The species is frequently cited as being used in herbal medicine since the beginning of the first century AD. Extracts from A. vera are widely used in the cosmetics and alternative medicine industries, being marketed as variously having rejuvenating, healing, or soothing properties. There is, however, little scientific evidence of the effectiveness or safety of Aloe vera extracts for either cosmetic or medicinal purposes, and what positive evidence is available is frequently contradicted by other studies.
Aloe vera is a stemless or very short-stemmed succulent plant growing to 60–100 cm (24–39 in) tall, spreading by offsets. The leaves are thick and fleshy, green to grey-green, with some varieties showing white flecks on their upper and lower stem surfaces. The margin of the leaf is serrated and has small white teeth. The flowers are produced in summer on a spike up to 90 cm (35 in) tall, each flower being pendulous, with a yellow tubular corolla 2–3 cm (0.8–1.2 in) long. Like other Aloe species, Aloe vera forms arbuscular mycorrhiza, a symbiosis that allows the plant better access to mineral nutrients in soil.
Aloe vera leaves contain phytochemicals under study for possible bioactivity, such as acetylated mannans, polymannans, anthraquinone C-glycosides, anthrones, anthraquinones, such as emodin, and various lectins.
Taxonomy and etymology
The species has a number of synonyms: A. barbadensis Mill., Aloe indica Royle, Aloe perfoliata L. var. vera and A. vulgaris Lam. Common names include Chinese Aloe, Indian Aloe, True Aloe, Barbados Aloe, Burn Aloe, First Aid Plant. The species epithet vera means "true" or "genuine". Some literature identifies the white-spotted form of Aloe vera as Aloe vera var. chinensis; however, the species varies widely with regard to leaf spots and it has been suggested that the spotted form of Aloe vera may be conspecific with A. massawana. The species was first described by Carl Linnaeus in 1753 as Aloe perfoliata var. vera, and was described again in 1768 by Nicolaas Laurens Burman as Aloe vera in Flora Indica on 6 April and by Philip Miller as Aloe barbadensis some ten days after Burman in the Gardener's Dictionary.
Techniques based on DNA comparison suggest Aloe vera is relatively closely related to Aloe perryi, a species endemic to Yemen. Similar techniques, using chloroplast DNA sequence comparison and ISSR profiling have also suggested it is closely related to Aloe forbesii, Aloe inermis, Aloe scobinifolia, Aloe sinkatana, and Aloe striata. With the exception of the South African species A. striata, these Aloe species are native to Socotra (Yemen), Somalia, and Sudan. The lack of obvious natural populations of the species has led some authors to suggest Aloe vera may be of hybrid origin.
The natural range of A. vera is unclear, as the species has been widely cultivated throughout the world. Naturalised stands of the species occur in the southern half of the Arabian Peninsula, through North Africa (Morocco, Mauritania, Egypt), as well as Sudan and neighbouring countries, along with the Canary, Cape Verde, and Madeira Islands. This distribution is somewhat similar to the one of Euphorbia balsamifera, Pistacia atlantica, and a few others, suggesting that a dry sclerophyll forest once covered large areas, but has been dramatically reduced due to desertification in the Sahara, leaving these few patches isolated. Several closely related (or sometimes identical) species can be found on the two extreme sides of the Sahara: dragon trees (Dracaena) and Aeonium being two of the most representative examples.
The species was introduced to China and various parts of southern Europe in the 17th century. The species is widely naturalised elsewhere, occurring in temperate and tropical regions of Australia, Barbados, Belize, Nigeria, Paraguay and the United States The actual species' distribution has been suggested to be the result of human cultivation.
Aloe vera has been widely grown as an ornamental plant. The species is popular with modern gardeners as a putatively medicinal plant and for its interesting flowers, form, and succulence. This succulence enables the species to survive in areas of low natural rainfall, making it ideal for rockeries and other low water-use gardens. The species is hardy in zones 8–11, although it is intolerant of very heavy frost or snow. The species is relatively resistant to most insect pests, though spider mites, mealy bugs, scale insects, and aphid species may cause a decline in plant health. In pots, the species requires well-drained, sandy potting soil and bright, sunny conditions; however, Aloe plants can burn under too much sun or shrivel when the pot does not drain the rain. The use of a good-quality commercial propagation mix or packaged "cacti and succulent mix" is recommended, as they allow good drainage. Terra cotta pots are preferable as they are porous. Potted plants should be allowed to completely dry prior to rewatering. When potted, aloes become crowded with "pups" growing from the sides of the "mother plant", they should be divided and repotted to allow room for further growth and help prevent pest infestations. During winter, Aloe vera may become dormant, during which little moisture is required. In areas that receive frost or snow, the species is best kept indoors or in heated glasshouses. Large-scale agricultural production of Aloe vera is undertaken in Australia, Bangladesh, Cuba, the Dominican Republic, China, Mexico, India, Jamaica, Kenya, Tanzania and South Africa, along with the USA to supply the cosmetics industry with Aloe vera gel.
Preparations made from Aloe vera are often referred to as "aloe vera". Scientific evidence for the cosmetic and therapeutic effectiveness of aloe vera is limited and when present is frequently contradictory. Despite this, the cosmetic and alternative medicine industries regularly make claims regarding the soothing, moisturizing, and healing properties of aloe vera  commercially advertised mainly for skin conditions such as sunburns, cold sores and frostbite. Aloe vera gel is also used commercially as an ingredient in yogurts, beverages, and some desserts; although at certain doses, its toxic properties could be severe whether ingested or topically applied. The same is true for the use of aloe latex - which can also be either topically applied or ingested. Nonetheless, its power in aiding with the regulation of bowels, epilepsy, depression, diabetes, multiple sclerosis, glaucoma, and a host of other ailments remains beneficial to humans. Other uses for extracts of Aloe vera include the dilution of semen for the artificial fertilization of sheep, as a fresh food preservative, or for water conservation in small farms. It has also been suggested that biofuels could be obtained from Aloe vera seeds. Aloe is also used as a food substance, possibly for its gelling properties.
Early records of Aloe vera use appear in the Ebers Papyrus from the 16th century BC, in both Dioscorides' De Materia Medica and Pliny the Elder's Natural History written in the mid-first century AD along with the Juliana Anicia Codex produced in 512 AD. The species is used widely in the traditional herbal medicine of many countries. Aloe vera, called kathalai in Ayurvedic medicine, is used as a multipurpose skin treatment. This may be partly due to the presence of saponin, a chemical compound that acts as an antimicrobial agent.
Aloin, a compound found in the exudate of some Aloe species, was the common ingredient in over-the-counter (OTC) laxative products in the United States prior to 2003, when the Food and Drug Administration ruled that aloin was a class III ingredient, thereby banning its use. Aloe vera has potential toxicity, with side effects occurring at some dose levels both when ingested or applied topically. Although toxicity may be less when aloin is removed by processing, Aloe vera that contains aloin in excess amounts may induce side effects. A two-year National Toxicology Program (NTP) study on oral consumption of nondecolorized whole leaf extract of Aloe vera found evidence of carcinogenic activity in male and female rats. The NTP says more information is needed to determine the potential risks to humans.
Aloe vera juice is marketed to support the health of the digestive system, but there is neither scientific evidence nor regulatory approval to support this claim. The extracts and quantities typically used for such purposes appear to be dose-dependent for toxic effects.
Aloe vera is used on facial tissues where it is promoted as a moisturiser and/or anti-irritant to reduce chafing of the nose. Cosmetic companies commonly add sap or other derivatives from Aloe vera to products such as makeup, tissues, moisturizers, soaps, sunscreens, incense, shaving cream, or shampoos. A review of academic literature notes that its inclusion in many hygiene products is due to its "moisturizing emollient effect".
In 2011, the NTP carried out a series of short- and long-term carcinogenicity studies of a nondecolorized whole leaf extract of Aloe barbadensis miller (Aloe vera) in rats and mice, in which the extracts were fed to the rodents in drinking water. The studies found "clear evidence of carcinogenic activity" in the rats, but "no evidence of carcinogenic activity" in the mice. Both the mice and rats had increased amounts of noncancerous lesions in various tissues. The NTP believes further studies of oral preparations of aloe are important, as are studies of the oral exposure of humans to aloe; topical preparations are still considered safe.
Oral ingestion of Aloe vera may also cause diarrhea, which in turn can lead to electrolyte imbalance, kidney dysfunction, dry mouth, headache, and nausea, while topical application may induce contact dermatitis, erythema, or phototoxicity.
Research into medical uses
Two 2009 reviews of clinical studies determined that all were too small and faulty to allow strong conclusions to be drawn from them, but concluded, "there is some preliminary evidence to suggest that oral administration of aloe vera might be effective in reducing blood glucose in diabetic patients and in lowering blood lipid levels in hyperlipidaemia. The topical application of aloe vera does not seem to prevent radiation-induced skin damage. It might be useful as a treatment for genital herpes and psoriasis. The evidence regarding wound healing is contradictory. More and better trial data are needed to define the clinical effectiveness of this popular herbal remedy more precisely."  One of the reviews found that Aloe has not been proven to offer protection for humans from sunburn, suntan, or other damage from the sun.
A 2007 review of aloe vera's use in burns concluded, "cumulative evidence tends to support that aloe vera might be an effective interventions used in burn wound healing for ﬁrst- to second-degree burns. Further, well-designed trials with sufﬁcient details of the contents of aloe vera products should be carried out to determine the effectiveness of aloe vera. Topical application of aloe vera may also be effective for genital herpes and psoriasis.
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- Herbal medicine
- Medicinal plants
- Museo de Aloe de Lanzarote, Aloe vera museum in the Canary Islands, Spain
- Succulent plants
- Akinyele BO, Odiyi AC (2007). "Comparative study of the vegetative morphology and the existing taxonomic status of Aloe vera L.". Journal of Plant Sciences 2 (5): 558–563. doi:10.3923/jps.2007.558.563.
- Ernst E (2000). "Adverse effects of herbal drugs in dermatology". Br J Dermatol 143 (5): 923–929. doi:10.1046/j.1365-2133.2000.03822.x.
- Marshall JM (1990). "Aloe vera gel: what is the evidence?". Pharm J 244: 360–362.
- Boudreau MD, Beland FA (2006). "An Evaluation of the Biological and Toxicological Properties of Aloe Barbadensis (Miller), Aloe Vera". Journal of Environmental Science and Health Part C 24: 103–154.
- Vogler BK, Ernst E (Oct 1999). "Aloe vera: a systematic review of its clinical effectiveness". Br J Gen Pract 49 (447): 823–8. PMC 1313538. Retrieved 6 March 2013.
- Yates A. (2002) Yates Garden Guide. Harper Collins Australia
- Random House Australia Botanica's Pocket Gardening Encyclopedia for Australian Gardeners Random House Publishers, Australia
- Gong M, Wang F, Chen Y (January 2002). "[Study on application of arbuscular-mycorrhizas in growing seedings of Aloe vera]". Zhong yao cai = Zhongyaocai = Journal of Chinese medicinal materials (in Chinese) 25 (1): 1–3. PMID 12583231.
- King GK, Yates KM, Greenlee PG, et al. (1995). "The effect of Acemannan Immunostimulant in combination with surgery and radiation therapy on spontaneous canine and feline fibrosarcomas". Journal of the American Animal Hospital Association 31 (5): 439–47. PMID 8542364.
- Eshun, K.; He, Q. (2004). "Aloe Vera: A Valuable Ingredient for the Food, Pharmaceutical and Cosmetic Industries—A Review". Critical Reviews in Food Science and Nutrition 44 (2): 91–96. doi:10.1080/10408690490424694. PMID 15116756.
- "Aloe vera, African flowering plants database". Conservatoire et Jardin botaniques de la Ville de Genève. Retrieved 2008-06-20.
- "Taxon: Aloe vera (L.) Burm. f.". Germplasm Resources Information Network, United States Department of Agriculture. Retrieved 2008-07-16.
- Ombrello, T. "Aloe vera". Archived from the original on 5 July 2008. Retrieved 2008-06-21.
- Liao Z, Chen M, Tan F, Sun X, Tang K (2004). "Microprogagation of endangered Chinese aloe". Plant Cell, Tissue and Organ Culture 76 (1): 83–86.
- Jamir T. T., Sharma H. K., Dolui A. K. (1999). "Folklore medicinal plants of Nagaland, India". Fitoterapia 70 (1): 395–401. doi:10.1016/S0367-326X(99)00063-5.
- Barcroft and Myskja (2003) Aloe Vera: Nature's Silent Healer. BAAM, USA. ISBN 0-9545071-0-X
- Wang H, Li F, Wang T, et al. (September 2004). "[Determination of aloin content in callus of Aloe vera var. chinensis]". Zhong yao cai = Zhongyaocai = Journal of Chinese medicinal materials (in Chinese) 27 (9): 627–8. PMID 15704580.
- Gao W, Xiao P (November 1997). "[Peroxidase and soluble protein in the leaves of Aloe vera L. var. chinensis (Haw.)Berger]". Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica (in Chinese) 22 (11): 653–4, 702. PMID 11243179.
- Lyons G. "The Definitive Aloe vera, vera?". Huntington Botanic Gardens. Archived from the original on 25 July 2008. Retrieved 2008-07-11.
- Linnaeus, C. (1753). Species plantarum, exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas. Vol. 2 pp. [i], 561–1200, [1–30, index], [i, err.]. Holmiae [Stockholm]: Impensis Laurentii Salvii.
- Newton L. E. (1979). "In defense of the name Aloe vera". The Cactus and Succulent Journal of Great Britain 41: 29–30.
- Darokar MP, Rai R, Gupta AK, Shasany AK, Rajkumar S, Sunderasan V, Khanuja SPS (2003). "Molecular assessment of germplasm diversity in Aloe spp. using RAPD and AFLP analysis". J Med. Arom. Plant Sci. 25 (2): 354–361.
- Treutlein J., Smith G. F. S., van Wyk B. E., Wink W. (2003). "Phylogenetic relationships in Asphodelaceae (Alooideae) inferred from chloroplast DNA sequences (rbcl, matK) and from genomic finger-printing (ISSR)". Taxon 52: 193.
- Jones WD, Sacamano C. (2000) Landscape Plants for Dry Regions: More Than 600 Species from Around the World. California Bill's Automotive Publishers. USA.
- Farooqi and Sreeramu (2001) Cultivation of Medicinal and Aromatic Crops (Revised Edition). Orient Longman, India. p. 25.
- "Global Compendium of Weeds Aloe vera (Aloeaceae)". Global Compendium of Weeds. Archived from the original on 3 June 2008. Retrieved 2008-06-20.
- "BBC Gardening, Aloe vera". British Broadcasting Corporation. Retrieved 2008-07-11.
- "Pest Alert: Aloe vera aphid Aloephagus myersi Essi.". Florida Department of Agriculture and Consumer Services. Archived from the original on 12 June 2008. Retrieved 2008-07-11.
- "Kemper Center for Home Gardening: Aloe vera". Missouri Botanic Gardens, USA. Retrieved 2008-07-11.
- Coleby-Williams, J. "Fact Sheet: Aloes". Gardening Australia, Australian Broadcasting Corporation. Archived from the original on 6 July 2008. Retrieved 2008-07-08.
- "Aloe vera producer signs $3m China deal". Australian Broadcasting Corporation. Retrieved 2008-07-08.
- "More Medicinal Plants Grow in Ciego de Ávila". invasor.cu. Retrieved 2008-06-25.[dead link]
- "Korea interested in Dominican 'aloe vera'". DominicanToday.com—The Dominican Republic News Source in English. Retrieved 2008-07-19.
- Vaibhav Varma. "India experiments with farming medicinal plants". channelnewsasia.com. Retrieved 2008-06-25.
- "Harnessing the potential of our aloe". Jamaica Gleaner, jamaica-gleaner.com. Retrieved 2008-07-19.
- "Kenya: Imported Gel Hurts Aloe Vera Market". allafrica.com. Retrieved 2008-06-25.
- "US Farms, Inc. – A Different Kind of Natural Resource Company". resourceinvestor.com. Retrieved 2008-07-19.
- "RHS Plant Selector Aloe vera AGM / RHS Gardening". Apps.rhs.org.uk. Retrieved 2012-11-09.
- Langmead, L; Feakins, RM; Goldthorpe, S; et al. (April 2004). "Randomized, double-blind, placebo-controlled trial of oral aloe vera gel for active ulcerative colitis". Alimentary pharmacology & therapeutics 19 (7): 739–47. doi:10.1111/j.1365-2036.2004.01902.x. PMID 15043514.
- Kunkel. G. Plants for Human Consumption. Koeltz Scientific Books 1984 ISBN 3-87429-216-9
- Reynolds, T. (2004) Aloes: The Genus Aloe. CRC Press
- Liza Armstrong. "Clean and green". Australian Broadcasting Corporation. Archived from the original on 24 May 2008. Retrieved 2008-06-20.
- "Yagua unveils cosmeceutical beverage". Decision News Media. Retrieved 2008-06-20.
- Cosmetic Ingredient Review Expert Panel (2007). "Final report on the safety assessment of AloeAndongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice, Aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract". Int J Toxicol 26 (Suppl 2): 1–50. doi:10.1080/10915810701351186. PMID 17613130.
- "Aloe". WebMD.
- Rodriguez F, Baldassarre H, Simonetti J, Aste F, Ruttle JL (1988). "Cervical versus intrauterine insemination of ewes using fresh or frozen semen diluted with Aloe vera gel". Theriogenology 30 (5): 843–54. doi:10.1016/S0093-691X(88)80046-3. PMID 16726526.
- Serrano, M; Valverde, JM; Guillén, F; Castillo, S; Martínez-Romero, D; Valero, D (May 2006). "Use of Aloe vera gel coating preserves the functional properties of table grapes". Journal of Agricultural and Food Chemistry 54 (11): 3882–6. doi:10.1021/jf060168p. PMID 16719510.
- "Water conservation". Chennai, India: The Hindu, India. 2008-07-10. Archived from the original on 2 August 2008. Retrieved 2008-07-14.
- Shukla, S. "Aloe Vera has biodiesel potential, reveals MSU study". The Indian Express. Retrieved 2008-06-21.
- "Kathalai". Tamilnadu.com. 7 February 2013.
- Food And Drug Administration, H. H. S. (2002). "Status of certain additional over-the-counter drug category II and III active ingredients. Final rule". Federal register 67 (90): 31125–31127. PMID 12001972.
- Bottenberg MM, Wall GC, Harvey RL, Habib S (October 2007). "Oral Aloe vera-induced hepatitis". Annals of Pharmacotherapy 41 (10): 1740–3. doi:10.1345/aph.1K132. PMID 17726067.
- "Aloe Vera – Side Effects and Cautions". National Center for Complementary and Alternative Medicine. Retrieved 2011-10-07.
- Boudreau, M.D; Beland, F.A; Nichols, J.A; Pogribna, M (2011), Toxicology and carcinogenesis studies of nondecolorized whole leaf extract of Aloe Barbadensis Miller (Aloe vera) in F344/N rates and B6C3F1 mice (Drinking water study), Peer review draft NTP TR 577, National Institutes of Health, retrieved 6 March 2013 NIH publication no. 11-5919
- "NTP Speaks about Aloe Vera". Niehs.nih.gov. Retrieved 2012-11-09.
- "Aloe (Aloe vera)". MayoClinic.com. 2012-09-01. Retrieved 2012-11-09.
- K, Eshun (2004). "Aloe vera: a valuable ingredient for the food, pharmaceutical and cosmetic industries--a review". Crit Rev Food Sci Nutr 44 (2): 91–6. doi:10.1080/10408690490424694. PMID 15116756.
- Feily, A; Namazi, MR (2009). "Aloe vera in dermatology: a brief review". G Ital Dermatol Venereol 144: 84–91.
- Maenthaisong, Ratree; Chaiyakunapruk, Nathorn; Niruntraporn, Surachet; Kongkaew, Chuenjid (September 2007). "The efficacy of Aloe vera used for burn wound healing: A systematic review". Burns 33 (6): 713–718. doi:10.1016/j.burns.2006.10.384. PMID 17499928. Retrieved 5 March 2013.