Aloe Vera: History and Traditional Use
The plant on the windowsill has two histories, not one. For most of the last two thousand years "aloes" meant a hard, dark, intensely bitter lump — the dried yellow sap of the leaf, shipped from Socotra, Barbados and the Cape as one of the world's standard purgatives. The clear gel inside the same leaf, the substance most people now mean by aloe vera, entered medical writing only in the 1930s and became an industry after the 1970s. This article follows both stories from the plant's uncertain Arabian origins through Dioscorides and Pliny, the Arab physicians, Ayurveda and Chinese medicine, the colonial drug trade, the chemists who isolated aloin in 1851 and acemannan in the 1980s, and the regulators who from 2002 drew a sharp line between the two substances. Where a story is legend, we call it one.
Table of Contents
- Origins, Botany and the Two Names
- One Leaf, Two Medicines: Latex and Gel
- The Ancient Mediterranean: Egypt, Dioscorides and Pliny
- Socotra, the Arab Physicians and the Alexander Legend
- Kumari and Lu Hui: Aloe in Ayurveda and Chinese Medicine
- Bitter Aloes: Barbados, Curaçao and the Cape
- The Chemists: Aloin (1851) to Acemannan (1980s)
- The Gel Era: From Radiation Burns (1935) to Clinical Trials
- Regulators Draw the Line: 2002, 2013 and After
- Aloe Today: Tradition and Evidence
- Key Research Papers
- Connections
- Featured Videos
Origins, Botany and the Two Names
Aloe vera is a stemless succulent of the family Asphodelaceae — a rosette of thick, spine-edged leaves and a spike of tubular yellow flowers — one of several hundred species in an almost entirely African genus. Where this species came from is a surprisingly hard question. It grows today, apparently wild, around the Mediterranean, in the Canaries, in India and across the tropical Americas, but every one of those populations is best explained as an escape from cultivation. The plant is, in the botanist's word, a cultigen — propagated by people for so long that its original home must be inferred rather than visited.
The inference now rests on DNA. A 2015 study of the evolutionary tree of the aloes, led by botanists at Kew and in Copenhagen, placed Aloe vera's closest relatives in the Arabian Peninsula, at the northern edge of a genus that arose in southern Africa some sixteen million years ago. The same study offered an unglamorous explanation for why this one species, out of hundreds of chemically similar aloes, conquered the world: not special virtue but geography — it grew beside the oldest trade routes linking Arabia, the Red Sea and the Mediterranean, and was among the first aloes carried into cultivation.
The plant carries two scientific names. Linnaeus described it in 1753 as a variety, Aloe perfoliata var. vera. In April 1768 the Dutch botanist Nicolaas Laurens Burman raised it to a species as Aloe vera, and about ten days later Philip Miller of the Chelsea Physic Garden published the same plant as Aloe barbadensis, "the aloe of Barbados" — recording where the English drug then came from, not where the plant began. Burman's name has priority, so the correct name is Aloe vera (L.) Burm.f., but Aloe barbadensis Miller lived on in pharmacopoeias and on the American regulatory documents described later. One confusion to clear away at the start: the fragrant "aloes" of the Bible, burned alongside myrrh, is not this plant at all but agarwood, the resinous heartwood of an Asian tree.
One Leaf, Two Medicines: Latex and Gel
Nothing in aloe's history makes sense unless the two products of the leaf are kept apart. Cut a leaf across and a thin layer of bitter yellow sap beads out from a ring of vessels just beneath the green rind. This is the latex. Dried in the sun or boiled down, it sets into the dark, glassy, foul-tasting mass that pharmacists for centuries simply called aloes. Its active constituents are anthraquinones — chiefly aloin, which gut bacteria convert into a strong stimulant laxative. Every ancient and early-modern reference to "aloes" taken by mouth means this substance.
Inside that ring, filling the centre of the leaf, is a colourless, slippery jelly: the gel, or inner-leaf parenchyma. It is about 99 per cent water; the rest is mostly long-chain sugars (polysaccharides), of which the acetylated mannan later named acemannan is the best known. It is not purgative and is what is rubbed on burns and bottled as drinks and lotions today. The ancients did lay fresh leaves on wounds — Pliny says so — but the gel as an article of commerce and a subject of research is a twentieth-century creation.
The rule this article keeps returning to: latex is the old drug, taken by mouth and purgative; gel is the new one, applied to the skin and soothing. A "whole-leaf" product, in which the entire leaf is ground up, contains both — the distinction modern regulators seized upon.
The Ancient Mediterranean: Egypt, Dioscorides and Pliny
Aloe's history is often opened with the Ebers Papyrus, the Egyptian medical scroll conventionally dated to about 1550 BCE, which is said to name the plant among its several hundred remedies. Handle the claim with care: aloe appears in modern summaries of the papyrus' plant drugs, but matching ancient Egyptian plant names to modern species is uncertain and Egyptologists flag the translations as tentative. The honest statement is that aloe may be one of its plants, not that an Egyptian recipe survives.
The first Mediterranean text that unmistakably describes the plant is the De Materia Medica of Dioscorides, the Greek army physician who compiled his drug encyclopaedia in the first century CE. Aloe is absent from the earlier Hippocratic writings and from Theophrastus' botany, which suggests it reached Greek medicine late, through eastern trade. Dioscorides gives a recognisable portrait — a leaf like the squill's, thick and curving back, with short blunt thorns along the edges, a plant that "has an oppressive smell and tastes very bitter" — and says it is "abundant in India, where comes the sap," growing also in Arabia. What he prescribes is the dried juice: taken with water or honey it "stimulates the bowel," three drams alone "will purge perfectly," it "draws out bile and phlegm," and mixed with wine it is rubbed in to stop hair falling out. He adds that leaf material chopped and laid on wounds is "very good for healing" them — the one gel-like use in the ancient record. Some scholars suspect the aloe chapter was a later insertion; even so, it stood in every copy through the Middle Ages and shaped European practice for fifteen hundred years.
Pliny the Elder's Natural History, finished in 77 CE, devotes a chapter of Book 27 to "the aloe: twenty-nine remedies." He repeats the resemblance to squill, says the most esteemed aloes came from India, and confirms that fresh leaves were applied to wounds, the leaf and juice being "glutinous to a marvellous degree." His uses are Dioscorides' with additions: a purgative in pills with boiled honey or turpentine, a remedy that gently arrests bleeding from haemorrhoids, and an injection in dysentery. From these two authors aloes passed into the whole Byzantine, Arabic and Latin tradition as a standard bitter purge.
Socotra, the Arab Physicians and the Alexander Legend
For the medieval world the best aloes came from one place: Socotra, the arid island off the Horn of Africa at the mouth of the Gulf of Aden, where several aloe species (chiefly Aloe perryi, a close relative rather than Aloe vera itself) grow wild. Arabic writers made its reputation: Ibn Sina (Avicenna, 980–1037) identified the best aloe with the island, and the Andalusian botanist Ibn al-Baitar (1197–1248) ranked Socotran aloes above Yemen's. "Socotrine aloes" remained the pharmacopoeial gold standard into the nineteenth century, though by then much of what was sold under the name came from the Arabian mainland and East Africa.
Around Socotra grew the most famous story in aloe's history, and it deserves to be told as what it is. According to the legend, Aristotle urged his former pupil Alexander the Great to seize the island so that his army would have a secure supply of aloes for wounds. The tale is genuinely old — the twelfth-century geographer al-Idrisi writes that "acting on the advice of Aristotle, Alexander removed the inhabitants from their island, and established in their place a colony of Ionians, to whom he entrusted the care of cultivating aloes." But no ancient historian of Alexander mentions any such expedition, and Henry Yule, the Victorian editor of Marco Polo, judged it "probably a fable, but invented to account for facts" — the facts being that medieval Socotra really did have a Greek-speaking Christian population and really did export aloes as its chief product. The legend is an explanation dressed as history: it tells us how valuable aloes were, not what Alexander did.
European traders followed the Arabs: Samuel Purchas' 1625 collection of voyages records English merchants bargaining with the ruler of Socotra for aloes. Yet the island's trade never grew; by 1833 it exported a mere two tons, and later in the century production ceased altogether, undercut by plantations on the far side of the world.
Kumari and Lu Hui: Aloe in Ayurveda and Chinese Medicine
Dioscorides said the sap came from India, and the plant has been naturalised there so long that it is often taken for native. Botanically it is not, and the textual record agrees: aloe does not appear in the Vedas and is not prominent in the oldest Sanskrit medical compendia. It enters the Ayurvedic literature later, under the name kumari — "the maiden" — traditionally explained by its use in complaints of young women, and in Hindi as ghritkumari. In the Ayurvedic framework it is classed as cooling and bitter and is said to pacify all three doshas, the constitutional energies of that system — the categories Ayurveda itself used, recorded here as tradition rather than physiology. Its Indian uses mirror the leaf's two substances: the dried juice as a purgative and menstrual regulator, the fresh pulp for burns and non-healing sores, and fermented tonics such as kumari asava for liver and digestive complaints. Several historians think the drug reached India through Arab traders.
China received aloe by the same seaborne routes. In Chinese medicine the dried latex is lu hui (芦荡), and the name appears, in variant characters, in the materia medica of the Tang and Song periods: the Tang-era Yaoxing Lun (Treatise on the Nature of Medicines) lists it, and the Kaibao Bencao, the official pharmacopoeia compiled in 973–974, records it under further names. Chinese physicians classed it as bitter and cold and used it, in small doses, for stubborn constipation, for what that system calls "liver fire" with heat in the intestines, and for intestinal worms in children. In both India and China the substance was the imported, dried latex; the gel industry now flourishing in both countries is a twentieth-century import from the West.
Bitter Aloes: Barbados, Curaçao and the Cape
Spanish and Portuguese ships carried Aloe vera to the Americas early, and the English turned it into a plantation crop. Barbados was growing aloes within about twenty years of the English settlement of 1627, and "Barbados aloes" was on the London market by 1693, shipped, as the naturalist Samuel Dale noted in 1751, "in large gourds." The method hardly changed for three centuries: leaves were cut at the base and stood, cut end down, in a V-shaped trough so that the latex drained out over several hours; the yellow liquid was boiled down and poured into gourds or boxes to harden. This is the drug that gave the plant Miller's name barbadensis. Barbados aloes was thought harsher than Socotrine, but it was cheap and plentiful, and by the nineteenth century it was the aloes most people actually swallowed.
Two other sources completed the market. From the Dutch islands of Aruba, Bonaire and Curaçao came "Curaçao aloes," in the Dutch market by 1847 and in London from about 1876; Aruba built an economy on it, with aloe fields covering much of the island, the plant on its coat of arms, and in the early twentieth century a single island producer supplying a substantial share of the world's aloin. From South Africa came "Cape aloes," the dried bitter latex of a different species, Aloe ferox, first tapped commercially in 1761 — the technique, tradition holds, shown to a Cape farmer by an enslaved worker — and exported to Europe from the 1770s. Cape aloes remains a live industry today.
What all this trade supplied was a purgative. Aloes was among the commonest ingredients in the pills of the eighteenth and nineteenth centuries — in the "pil. aloes et myrrhae" of the British pharmacopoeias, in innumerable patent "family" pills, and, because it stimulates the pelvic organs, in preparations for suppressed menstruation, which made it a folk abortifacient and a recognised danger in pregnancy. Herbalists from Gerard to Culpeper repeated the classical uses. The drug was ordinary: a staple of every apothecary's jar, valued and disliked in equal measure.
The Chemists: Aloin (1851) to Acemannan (1980s)
The scientific chapter opens, as it does for so many old drugs, with a bitter crystal. In February 1851 the Edinburgh manufacturing chemists Thomas and Henry Smith announced in the Monthly Journal of Medical Science a "new principle in aloes, on which the cathartic properties of the drug appear to depend." They called it aloine: a neutral, deep-yellow crystalline substance, sparingly soluble in cold water and readily in hot, that produced the purgative effect of aloes in a fraction of the dose. Later chemists found that the aloin of different commercial sorts differed, and the form from Barbados aloes came to be called barbaloin; only in the twentieth century was its structure settled — a sugar bound directly to a three-ring anthraquinone skeleton — and its mechanism understood: it is inert until colon bacteria split it into a form that irritates the bowel wall into contraction and secretion. A 1987 survey found barbaloin in the latex of many but not all aloes, at widely varying concentrations.
The gel had to wait for a different chemistry. Its principal solids are polysaccharides, characterised in the 1970s and 1980s as chiefly a partially acetylated mannan — a long chain of mannose sugar units carrying acetyl groups — of which a Texas research group isolated and patented a purified fraction in 1987–1988 under the name acemannan. It became the focus of laboratory work on immune stimulation and wound healing, and in the early 1990s a veterinary preparation received a conditional US licence for fibrosarcoma in dogs and cats; the human evidence remains much thinner. Reviewers have since catalogued dozens of minor gel constituents without any one proving to be "the" active ingredient, and the most careful of them, from Grindlay and Reynolds in 1986 to Reynolds and Dweck in 1999, made the same point: the gel's composition varies enormously with the plant's age, the season and above all with processing and storage, which is why so many studies of it disagree.
The Gel Era: From Radiation Burns (1935) to Clinical Trials
The modern reputation of aloe gel can be dated with unusual precision. In 1935 two American physicians, C. E. Collins and Creston Collins, published in the American Journal of Roentgenology a two-page report titled "Roentgen dermatitis treated with fresh whole leaf of Aloe vera," describing a patient whose chronic X-ray-induced skin injury, unresponsive to conventional care, was reported to have healed under dressings of the fresh split leaf. Radiation injury was a pressing new problem, and the report was followed by a scatter of case reports and small animal studies through the 1930s and 1940s. The evidence was anecdotal, but it moved the gel from folk remedy to medical curiosity and fixed the association between aloe and burns that has persisted ever since.
Commerce caught up slowly. Fresh gel spoils within hours, and an industry could not exist until stabilising methods — pasteurisation, preservatives, freeze-drying, powders — were worked out from the 1950s onward; the Aruban producers, who had made aloin for pharmacists since the 1890s, turned to cosmetic gel in 1968, a decade before the rest of the world followed. By the 1980s aloe gel was in moisturisers, sunburn lotions, shampoos and "aloe juice" drinks, and marketing claims raced far ahead of evidence — what Grindlay and Reynolds' 1986 review called, with some exasperation, "the Aloe vera phenomenon."
Properly controlled trials began in the 1980s and 1990s, mostly small and mostly on the skin. The first systematic review of the clinical literature, by Vogler and Ernst in 1999, found ten controlled trials and concluded that oral aloe might help lower blood glucose and lipids, that topical aloe might be effective for genital herpes and psoriasis, that its effect on wound healing was unclear, and — in a pointed reversal of the 1935 story — that it was not an effective preventative for radiation-induced skin injury; "there are major caveats," the authors wrote, "associated with all of these statements." A 2007 systematic review of burns pooled four trials in 371 patients and found healing of first- and second-degree burns about nine days faster with aloe than with controls, while warning that the trials were small, used different products and were of poor quality. Ninety years after Collins and Collins, the best-supported use of the gel is still the one their report described.
Regulators Draw the Line: 2002, 2013 and After
While the gel rose, the old drug fell. Aloes latex stayed in over-the-counter laxatives well into the twentieth century, but anthraquinone laxatives as a class came under scrutiny in the 1990s over genotoxicity — the possibility of damaging DNA. In June 1998 the United States Food and Drug Administration reclassified aloe from its approved category to "more data needed" and asked manufacturers for studies of mutagenicity and carcinogenicity. None were submitted. On 9 May 2002 the FDA published a final rule declaring aloe (including aloe extract and aloe flower extract) and cascara sagrada "not generally recognized as safe and effective" as over-the-counter stimulant laxatives, effective 5 November 2002. The substance Dioscorides recommended to "purge perfectly" could no longer be sold as a non-prescription laxative in the United States — not because it had been shown to be harmful, but because nobody had shown it to be safe.
The studies the FDA had asked for were eventually done by a government laboratory. The National Toxicology Program fed a non-decolourised whole-leaf extract of Aloe barbadensis Miller — leaf including its latex, and therefore its aloin — to rats and mice in drinking water for two years. Its Technical Report 577, published in 2013 with a paper in Toxicological Sciences, reported "clear evidence of carcinogenic activity" in male and female rats, which developed adenomas and carcinomas of the large intestine, and no evidence in mice. This is animal data at high, lifelong doses, with no comparable human evidence; but it was enough for the International Agency for Research on Cancer, meeting in 2013 and publishing in 2016, to classify Aloe vera whole-leaf extract as Group 2B, "possibly carcinogenic to humans," and for California to add it to its Proposition 65 list in December 2015. Both tied the finding to the anthraquinone-bearing whole leaf: "decolourised" inner-leaf gel, filtered through charcoal to remove aloin, was outside the classification. The line between latex and gel is now written into regulation.
Europe went further and then retreated: a March 2021 European Commission ban on aloe-leaf preparations containing hydroxyanthracene derivatives in foods was annulled by the EU General Court in November 2024, which ruled that an absence of data had been treated as proof of harm. The European Medicines Agency's herbal monograph still allows dried aloe leaf juice only for short-term use in occasional constipation, and not in children under twelve. On both sides of the Atlantic the latex is a real drug, treated as one.
Aloe Today: Tradition and Evidence
Set the two histories side by side and a pattern emerges that is unusual among medicinal plants. For the latex, tradition and modern science agree completely about what it does — it is a powerful purgative, exactly as Dioscorides, Ibn Sina, the Ayurvedic and Chinese physicians and every apothecary since have said — and modern science has simply decided that such a purgative, with an unresolved cancer signal in rats, is not something to sell over the counter. The old drug was not wrong; it was retired. For the gel, tradition offered very little — a line in Pliny about fresh leaves on wounds — and the modern reputation was built almost from nothing in the ninety years after 1935, first by case reports, then by an industry, and only lately by trials, which so far support modest benefit for minor burns and superficial wounds and not much else.
What survives from the long history is worth keeping. The plant is, as the Kew phylogeny showed, the aloe of the trade routes rather than of any special virtue; its sister species carry the same chemistry. Its two names commemorate a Dutch botanist and a Caribbean plantation. Its most famous story, Alexander's conquest of Socotra, is a medieval fable that tells the truth about the drug's value. And its central lesson, repeated by every careful reviewer since 1986, is that "aloe" on a label tells you almost nothing until you know which part of the leaf, processed how, and whether it is going on the skin or into the mouth.
Key Research Papers
The list covers the studies that settled the plant's origin and trade history, the major reviews of the gel and its chemistry, the first systematic reviews of the clinical trials, and the toxicology behind the regulatory decisions on the latex. Historical primary texts (Dioscorides, Pliny, al-Idrisi, the 1851 Smith report, the 1935 Collins report) are named in the article, not cited here.
- Grace OM, Buerki S, Symonds MRE, Forest F, van Wyk AE, et al. (2015). Evolutionary history and leaf succulence as explanations for medicinal use in aloes and the global popularity of Aloe vera. BMC Evolutionary Biology. — doi:10.1186/s12862-015-0291-7
- Grace OM (2011). Current perspectives on the economic botany of the genus Aloe L. (Xanthorrhoeaceae). South African Journal of Botany. — doi:10.1016/j.sajb.2011.07.002
- Grindlay D, Reynolds T (1986). The Aloe vera phenomenon: a review of the properties and modern uses of the leaf parenchyma gel. Journal of Ethnopharmacology. — PubMed PMID: 3528673
- Reynolds T, Dweck AC (1999). Aloe vera leaf gel: a review update. Journal of Ethnopharmacology. — doi:10.1016/S0378-8741(99)00085-9
- Groom Q, Reynolds T (1987). Barbaloin in Aloe species. Planta Medica. — doi:10.1055/s-2006-962735
- Vogler BK, Ernst E (1999). Aloe vera: a systematic review of its clinical effectiveness. British Journal of General Practice. — PubMed PMID: 10885091
- Maenthaisong R, Chaiyakunapruk N, Niruntraporn S, Kongkaew C (2007). The efficacy of aloe vera used for burn wound healing: a systematic review. Burns. — doi:10.1016/j.burns.2006.10.384
- 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. — doi:10.1080/10590500600614303
- Boudreau MD, Mellick PW, Olson GR, Felton RP, Thorn BT, et al. (2013). Clear evidence of carcinogenic activity by a whole-leaf extract of Aloe barbadensis Miller (Aloe vera) in F344/N rats. Toxicological Sciences. — PubMed PMID: 22968693
- Guo X, Mei N (2016). Aloe vera: a review of toxicity and adverse clinical effects. Journal of Environmental Science and Health, Part C. — doi:10.1080/10590501.2016.1166826