Aloe Vera

Aloe vera (L.) Burm.f. belongs to Asphodelaceae, in the order Asparagales, according to Kew’s Plants of the World Online (POWO). Some sources, including LiverTox, still place aloes in the lily family, and some papers and the industry’s own council use Xanthorrhoeaceae, so labels and studies disagree. Linnaeus first described the plant in 1753 as a variety, Aloe perfoliata var. vera, and it was raised to a species in Flora Indica in 1768. In the same year Philip Miller published the name Aloe barbadensis. POWO treats that name as one of 17 synonyms of Aloe vera, but it lives on in commerce, in the European pharmacy name Barbados aloes, and in the German name Curaçao-Aloe. The International Aloe Science Council (IASC), the industry’s trade body, notes that aloe vera is one of roughly 400 or more Aloe species and the one most used in consumer products, and that CITES, the treaty on trade in endangered species, lists every other aloe species but not aloe vera. NCCIH also lists Aloe arborescens and Aloe africana among the plants sold as aloe, so a product’s species matters.

POWO describes a short-stemmed, shrubby aloe that suckers freely and forms dense clumps. The leaves are succulent and erect in a dense rosette, grayish green, up to about 50 cm long, sometimes flecked with white, with pinkish margins carrying many small spines. Yellow, tubular flowers up to 3 cm long, with the anthers and stigma protruding, are borne in cylindrical racemes on a branched stalk up to 90 cm tall. The Missouri Botanical Garden notes that only mature plants flower, typically in summer, and that potted plants bloom only in sunny, near-ideal conditions, which is why many windowsill aloes never do. The wild plant grows in desert and dry shrubland, and NCCIH notes that aloe is grown in subtropical regions worldwide, including the southern border areas of Texas, New Mexico, Arizona, and California. The IASC lists commercial plantations in the United States, Central and South America, China, India, Africa, the Caribbean, Australia, and the Asian tropics.

The leaf is where gel and latex part company. EMA’s assessment report explains that pharmaceutical aloes is made by cutting the leaf across near its base and tilting it so that the juice held in specialized pericyclic cells, and sometimes the neighboring tissue, drains out over about six hours; the juice is then dried, with or without heat. The gel is a colorless mucilage from the large parenchyma cells in the center of the leaf, harvested by filleting away the green outer layers, and EMA notes that whether the gel is free of anthranoids depends on whether the cells beneath the rind are also removed. The IASC describes the latex as a bitter, yellow-brown to reddish substance found between the rind and the inner leaf. So a kitchen leaf, sliced and squeezed, delivers some of each.

Chemically, the two layers have little in common. EMA lists the active constituents of Barbados aloes as anthrone C-glycosides: aloin A and aloin B, together called barbaloin, plus hydroxyaloins and their esters, small amounts of the free compounds aloe-emodin and chrysophanol, and chromones called aloeresins. The European Pharmacopoeia requires Barbados aloes, the dried juice of Aloe barbadensis, to contain at least 28% hydroxyanthracene derivatives calculated as barbaloin, and Cape aloes, made mainly from Aloe ferox, at least 18%. The gel is mostly water with polysaccharides. The IASC uses acemannan, an acetylated glucomannan, as the chemical marker of genuine aloe vera and says products without it should not be called aloe vera. LiverTox counts more than 75 identified substances in aloe products, from vitamins, enzymes, and minerals to sugars, amino acids, and salicylic acid.

Aloe is among the oldest documented medicinal plants, though old sources rarely say which part of the leaf they meant. NCCIH notes that aloe was used in ancient Greece, Rome, Babylonia, and China, mainly for skin conditions, and was thought to promote wound healing and even prevent premature graying. EMA’s assessment report, drawing on a 1938 German text by Madaus, says the ancient Egyptians used aloe for battle wounds and infections and the early Greeks for blisters, burns, leg ulcers, and bowel and stomach complaints. It also repeats a legend that Aristotle persuaded Alexander the Great to conquer the island of Socotra to secure enough aloe to heal his soldiers’ wounds; EMA presents this as legend, not history. The Greek physician Dioscorides, writing between about 50 and 70 AD, described aloe as a purgative for the stomach and bowels and a remedy for jaundice, and said that applied outwardly it healed wounds, ulcers, and eye complaints, eased headache when rubbed on the forehead with vinegar and rose oil, and slowed hair loss when mixed with wine. EMA, citing Madaus, records aloe in use in England by the tenth century.

By the early twentieth century, Western pharmacy knew aloe mainly as a purgative. EMA quotes the British Pharmaceutical Codex of 1911, which gave a dose of 1 to 3 decigrams (2 to 5 grains) and noted that, because aloe congests the pelvis, it was also given with iron to bring on absent periods. The Dispensatory of the United States of 1918 called it a cathartic and recorded that it had once been almost universally believed to act on the womb, but judged it extremely doubtful that aloe did anything to the pelvic organs beyond its laxative effect. EMA’s assessors agreed, finding no plausible pharmacological basis for traditional uses in coughing up blood, jaundice, or gout. The dried latex also had a place in folk medicine for diabetes: EMA notes it is one of several traditional diabetes remedies in the Arabian Peninsula. Meanwhile the gel found a modern career in cosmetics, skin products, and drinks, and the IASC has run a certification seal since the 1980s, partly because adulteration and misbranding were common enough to need one.

Regulators began to restrict aloe laxatives in the 1990s. EMA reports that, prompted by laboratory signs of genotoxicity and a 1993 German endoscopy study linking pigmented colons with adenomas, Germany in 1996 limited the dose and duration of anthranoid laxatives and excluded children, pregnant women, and nursing mothers from aloe products. In June 1998 the FDA reclassified aloe, cascara sagrada, senna, and bisacodyl as needing more data and asked for studies of genotoxicity and cancer. It received data on senna and bisacodyl, but none on aloe or cascara. Its final rule, published on 9 May 2002 and effective 5 November 2002, declared aloe, aloe extract, and aloe flower extract not generally recognized as safe and effective for over-the-counter laxative use. FDA counted about 15 laxative products containing aloe at the time, which had to be reformulated or withdrawn. In Europe, EMA’s herbal committee adopted its first aloe monograph in 2006 and a revised one on 22 November 2016, keeping well-established use for short-term occasional constipation.

Attention then turned to whole-leaf products. The NTP published its two-year rat and mouse study in 2013, and IARC evaluated aloe the same year, classifying whole-leaf extract of aloe vera in Group 2B in Volume 108 of its monographs. In the European Union, the European Food Safety Authority (EFSA) concluded in 2017 that hydroxyanthracene derivatives should be regarded as genotoxic and carcinogenic unless shown otherwise, and Commission Regulation (EU) 2021/468 then banned aloe-emodin, emodin, and preparations from the leaf of Aloe species containing hydroxyanthracene derivatives from foods. An aloe drinks company challenged the ban, and on 13 November 2024 the EU General Court annulled the aloe-leaf entry, finding that the Commission could not prohibit these preparations regardless of how much of the compounds they contained. The Commission has appealed to the Court of Justice, so the legal position in the EU may still change. A darker chapter: MSKCC records that aloe injected as an alternative cancer treatment has caused several deaths.

Aloe latex works like senna, as a prodrug switched on by gut bacteria. EMA explains that aloins and related glycosides pass unabsorbed through the stomach and small intestine into the large intestine, where bacterial enzymes (EMA names a strain of Eubacterium) convert them into the active compound aloe-emodin-9-anthrone. That metabolite acts in two ways. It stimulates the muscle of the colon, speeding transit, and it changes fluid handling, blocking the absorption of water, sodium, and chloride, loosening the tight junctions between lining cells, and drawing water and salts into the bowel. The result, after the time needed to reach and activate in the colon, is a bowel movement six to twelve hours after a dose, which is why EMA advises taking aloes at night. Some aloe-emodin is absorbed: EMA cites animal studies in which at least 20–25% of an oral dose entered the body, though it is quickly converted to rhein and other metabolites. Metabolites can turn urine yellow or red-brown, which is harmless. EMA’s assessors acknowledge that adequate clinical trials of aloe are not available; its laxative effect is inferred from pharmacology, clinical experience, and data on related laxatives such as senna.

The same chemistry raises the long-term questions. EMA reports that four to thirteen months of anthranoid laxative use leads to pseudomelanosis coli, in which immune cells in the colon lining store a brown pigment and the bowel wall looks brown to black at colonoscopy; it is found in 62% of chronic users of these laxatives against 12–31% of people with chronic constipation, and fades six to twelve months after stopping. EMA’s monograph says several hydroxyanthracene derivatives were mutagenic and genotoxic in test-tube systems but that this was not proven in living animals. EFSA took a stricter view. As summarized in the 2024 General Court judgment, it concluded that emodin and aloe-emodin are genotoxic in vitro, that aloe-emodin was genotoxic in mice, and that aloe extracts depleted of hydroxyanthracenes still contained some other genotoxic component. NCCIH likewise notes laboratory hints that even decolorized extract might damage DNA, while a 2023 review of food-grade drinks with no more than 10 parts per million of aloin concluded that they were not genotoxic.

The gel works differently, and far less is proven. It is largely water held in a matrix of polysaccharides, of which acemannan is the main carbohydrate fraction, and on skin it feels cool and moist. Laboratory studies summarized by Memorial Sloan Kettering Cancer Center (MSKCC) suggest more specific effects: aloe oligosaccharides reduced the immune-suppressing signals that skin cells release after ultraviolet exposure, an aloe polysaccharide curbed the overgrowth of skin cells driven by the inflammatory messenger TNF-alpha in a psoriasis model, a polymer fraction protected the stomach lining from alcohol damage in animals, and acemannan stimulated immune cells in culture. These findings may help explain some clinical signals for burns, mouth sores, and gut symptoms, but they come from cells and animals. MSKCC also notes that aloe juice inhibited the drug-metabolizing enzymes CYP3A4 and CYP2D6 in the laboratory, with unknown clinical relevance.

Burns are the best-studied use of the gel, and the results are encouraging but soft. Maenthaisong and colleagues (Burns 2007) found four controlled studies with 371 patients; pooled, burns treated with aloe healed 8.79 days sooner than controls, but the products and outcome measures differed so much that the authors would only say aloe might be effective for first- and second-degree burns and called for better trials. Dat and colleagues’ Cochrane review (2012) of seven trials with 347 participants found that aloe mucilage did not heal burns significantly better than silver sulfadiazine cream, a standard burn treatment, and judged all the trials at high risk of bias. MSKCC summarizes a randomized study in which topical aloe outperformed silver sulfadiazine for second-degree burns, and NCCIH concludes that topical gel may speed burn healing and reduce burn pain. Applying cool gel to sunburn is a widespread home use, but the trials concern minor to partial-thickness burns in general. A sensible reading: for a small, superficial burn that has first been cooled under running water, gel is a reasonable soothing option; for anything larger or deeper, it is not a treatment.

Other skin and mouth uses rest on small trials. The Cochrane review found faster healing with aloe after hemorrhoid surgery but no difference after skin biopsies or in pressure ulcers, and in one trial of surgical wounds left to heal open, aloe delayed healing by about 30 days. NCCIH notes that two small studies suggest aloe gel, combined with other treatment, may improve acne, and that a small amount of research suggests help for genital herpes, psoriasis, oral submucous fibrosis, radiation skin damage, and mouth sores from dental appliances. MSKCC finds the radiation dermatitis trials mixed, but reports preliminary benefit against mouth sores caused by chemotherapy and radiotherapy and an aloe mouthwash that reduced plaque and gum inflammation about as well as chlorhexidine. For oral lichen planus, an immune condition of the mouth lining, Ali and Wahbi (Oral Diseases 2017) reviewed five trials and found weak evidence that aloe beats placebo and performs comparably to the steroid triamcinolone, though their pooled analyses were heterogeneous and, taken together, favored the comparison treatments; corticosteroids remain the standard.

Occasional constipation is the use regulators accept, and only for latex-derived aloes. EMA’s monograph allows a standardized dried aloe juice extract for short-term use in adults and adolescents over 12, at a dose supplying 10–30 mg of hydroxyanthracene derivatives, calculated as aloin, once at night, using the smallest dose that produces a comfortable soft-formed motion. It is not to be used for more than a week, two or three doses are usually enough, and EMA says it should be used only if a change of diet or a bulk-forming fiber has not worked. That acceptance rests on long marketing history and class effects shared with senna rather than on aloe trials, which EMA says are not available. In the United States, aloe can no longer be sold as an over-the-counter laxative ingredient, although LiverTox notes that extracts of the leaf-rind latex are still used in dietary supplements and, in small amounts, as a food flavoring. Better-studied options for constipation include fiber, senna, and prescription laxatives.

For the gut more broadly, oral gel products have a few promising small trials. Hong and colleagues (Journal of Neurogastroenterology and Motility 2018) pooled three placebo-controlled trials with 151 people with irritable bowel syndrome (IBS) and found modestly greater symptom improvement with aloe, a standardized mean difference of 0.41, with responders 1.69 times as likely as on placebo and no aloe-related adverse events; three small trials are a thin base, and NCCIH still says there is not enough reliable information on aloe for IBS or ulcerative colitis. For gastroesophageal reflux disease (GERD), Panahi and colleagues (Journal of Traditional Chinese Medicine 2015) randomized 79 people to an aloe syrup standardized to 5 mg of polysaccharide per milliliter (10 mL a day), omeprazole, or ranitidine for four weeks. Aloe reduced the frequency of all eight reflux symptoms measured, with no adverse events forcing withdrawal, but this was a pilot study with no placebo group. Neither IBS nor reflux has standardized aloe dosing, and persistent symptoms deserve a medical assessment.

Blood sugar is the most-studied oral use. NCCIH says a small amount of research suggests oral aloe may reduce blood sugar and HbA1c, a measure of average glucose, in people with diabetes, and that a specific gel product taken for eight weeks modestly reduced weight and fat mass in adults with overweight or obesity who had diabetes or prediabetes. Suksomboon and colleagues (Journal of Clinical Pharmacy and Therapeutics 2016) pooled eight trials with 470 patients. In prediabetes, aloe lowered fasting glucose slightly (by 0.22 mmol/L, about 4 mg/dL) without changing HbA1c; in type 2 diabetes, fasting glucose fell marginally and HbA1c fell by 11 mmol/mol, roughly one percentage point. The authors stressed high heterogeneity and limited evidence, and asked for well-powered trials of standardized products. Aloe is not a substitute for diabetes medicines, and anyone on them should check with a clinician first because glucose could fall further. Claims that aloe treats cancer are unsupported: MSKCC states that aloe is not an effective cancer treatment and that injected aloe has killed patients.

For skin use, a fresh leaf or a commercial gel are the usual choices. EMA describes how the bitter latex drains from a cut leaf held at a slant, and filleting off the green rind leaves the clear inner gel; the IASC notes that inner-leaf juice is made the same way, with the latex rinsed away. At home, that means cutting a mature outer leaf, letting the yellow sap run off, rinsing, and scooping or slicing out the clear gel for minor burns, sunburn, or dry skin. Test it on a small patch first, because burning, itching, and rashes occasionally occur. Commercial skin products vary in how much aloe they contain; for cosmetics, the IASC cites an industry limit of 50 parts per million of aloin set by the Cosmetic Ingredient Review. Cool a burn under running water first, keep gel off deep, blistered, or infected wounds, and stop if the skin becomes more red or painful. Clinical trials used a range of creams, gels, and dressings, so no single concentration is established.

Oral products are where labels matter most. The IASC describes two ways of making aloe juice. Inner-leaf juice comes from the gel after the rind is removed and the latex rinsed away. Whole-leaf juice comes from grinding entire leaves, treating the slurry with enzymes, and filtering it, usually through charcoal, to remove the latex; this decolorized or purified whole-leaf juice is a different material from the non-decolorized extract that caused tumors in rats. The IASC limit for aloin in products intended to be swallowed is under 10 parts per million, and its certification program tests products for aloin and for acemannan, the marker of real aloe. NCCIH notes that studies suggest oral aloe gel is safe in the short term, up to 42 days. Trial products varied widely, from a standardized syrup taken at 10 mL a day in the reflux study to specific gel products in diabetes research, and there is no standard oral dose. A label that says only “aloe,” or gives no aloin content, does not tell you which product you are buying.

Laxative preparations are a separate category. EMA’s monograph covers a dry extract standardized to 28.6–36.6% hydroxyanthracene derivatives, given to supply 10–30 mg a night for no more than a week, at the smallest effective dose. Because these products are not available as over-the-counter laxatives in the United States, people there are more likely to meet aloe latex in dietary supplements, which LiverTox notes can contain extracts of the leaf-rind latex, and where the anthranoid content may not be stated. Do not combine aloe latex with senna, cascara, frangula, rhubarb root, or bisacodyl; stacking stimulant laxatives multiplies cramping, diarrhea, and potassium loss. Do not raise the dose because one did not work by evening, since the effect takes six to twelve hours. If you need a laxative every day, EMA advises looking for the cause of the constipation. If one is needed at all, a bulk-forming fiber such as psyllium, or a well-characterized laxative chosen with a pharmacist, is usually a better first step than raw aloe.