Aloe Vera

Table of Contents

1. What Aloe Vera Is
2. Topical Uses (Skin)
3. Oral Use & the Latex Problem
4. How People Use It
5. Safety & Cautions
6. The Bottom Line
7. Key Research Papers
8. Connections
9. Featured Videos

What Aloe Vera Is

Aloe vera (botanical name Aloe barbadensis Miller) is a succulent plant with thick, spiky leaves that store a jelly-like fluid. Cut a leaf open and you'll find two distinct materials — and telling them apart is the single most important thing to understand about aloe.

• The inner-leaf gel. This is the clear, almost colorless jelly in the center of the leaf. It is mostly water, plus polysaccharides and other compounds. This is what goes into skin lotions, after-sun gels, and "aloe vera gel" drinks. On its own it is generally gentle.
• The latex (also called the sap or "aloe juice" in the old sense). This is a bitter, yellow liquid found in a thin layer just beneath the green leaf skin. It is rich in compounds called anthraquinones — chiefly aloin — which act as powerful stimulant laxatives. The latex is responsible for most of aloe's safety problems when taken by mouth.

"Whole-leaf" products contain both. When a leaf is ground up whole, the gel and the latex end up mixed together, so the product carries the latex's anthraquinones. By contrast, products labeled "inner-leaf," "decolorized," or "purified" are processed (often filtered through activated charcoal) to strip out most of the aloin. The difference is large: one analysis found roughly 100 times more aloin in non-decolorized whole-leaf extract than in decolorized extract. As you'll see, that processing step is central to how risky an oral aloe product is.

Topical Uses (Skin)

Putting aloe gel on the skin is where the plant earns its reputation. The evidence here is modest and somewhat mixed — most studies are small and not high quality — but the uses are plausible, the gel is inexpensive, and the risk is low. That combination is why it remains a common home remedy for minor skin troubles.

Minor burns and sunburn

This is aloe's best-supported use. A systematic review of controlled trials concluded that topical aloe vera may help first- and second-degree burns heal faster, though the authors stressed that the underlying trials were small and of generally poor quality, so the finding should be treated with caution. For a minor kitchen burn or an uncomfortable sunburn, people describe a cool aloe gel as soothing.

Wound healing

Aloe is often promoted to speed wound healing, and there's some supportive laboratory and traditional-use rationale. But the honest picture is that the evidence for serious or surgical wounds is weak — some studies have even suggested aloe could slow healing of certain surgical wounds. For everyday scrapes and minor irritation it is generally fine; it is not a substitute for proper medical wound care.

Moisturizing and psoriasis

Aloe gel is widely used as a light, non-greasy moisturizer, and many people find it calming for dry or irritated skin. There is also some evidence that topical aloe preparations can help psoriasis plaques, though results across studies are inconsistent. As with its other skin uses, aloe is a gentle soother that may help rather than a proven treatment.

Bottom line for the skin: aloe gel is a low-risk topical soother — most used for minor burns, sunburn, and dry or irritated skin — and the evidence behind it is modest.

Oral Use & the Latex Problem

Taking aloe by mouth is a completely different question from rubbing it on your skin, and this is the section to read carefully. The concerns here are real and are backed by regulators and toxicology studies — not internet rumor.

Aloe latex is a stimulant laxative — and the U.S. Food and Drug Administration pulled it

The anthraquinones in aloe latex (mainly aloin) are strong stimulant laxatives: they irritate the lining of the gut to force a bowel movement. For decades, aloe was an ingredient in over-the-counter laxatives. That ended in 2002, when the U.S. Food and Drug Administration ruled that aloe (and a related ingredient, cascara sagrada) was not generally recognized as safe and effective for over-the-counter (OTC) laxative use. The reason is telling: the U.S. Food and Drug Administration (FDA) had asked manufacturers to provide safety data — including studies on cancer risk and genetic damage — and the companies did not supply it. Rather than a clean bill of health, aloe laxatives left the market because their safety was never demonstrated.

A cancer signal in animal studies

The safety questions are not merely theoretical. The U.S. National Toxicology Program ran a two-year study in which rats drank water containing non-decolorized whole-leaf aloe vera extract. The result was "clear evidence of carcinogenic activity": the rats developed tumors of the large intestine (cecum and colon), progressing from tissue overgrowth to adenomas and carcinomas. On the strength of this and similar animal data, the International Agency for Research on Cancer (IARC) classifies whole-leaf extract of aloe vera as "possibly carcinogenic to humans" (Group 2B). There is not enough human data to know the risk in people, but a "clear evidence" animal carcinogenicity finding is a serious flag — and it points specifically at the aloin-containing whole-leaf and latex products, not the purified gel.

Where decolorized gel fits in

The animal cancer signal tracks with the anthraquinone (aloin) content, which is why decolorized / purified inner-leaf gel — with the aloin largely removed — is considered lower risk than whole-leaf or latex products. Lower risk is not no risk: in laboratory tests described in Guo and Mei’s 2016 toxicity review, the decolorized extract still caused mutations in mouse cells, and the authors concluded that aloe’s genetic toxicity “may not be eradicated completely” by removing the anthraquinones. The long-term safety of even oral gel is not fully established.

What oral gel has actually been studied for

Oral aloe gel (not latex) has been tested for metabolic conditions. For blood sugar, a 2016 systematic review and meta-analysis of 8 trials (470 patients) found that in people with prediabetes aloe improved fasting glucose but had no effect on hemoglobin A1c (HbA1c); in type 2 diabetes it improved HbA1c, while the improvement in fasting glucose was only marginal. Results varied widely between trials, so the authors called for high-quality, well-powered trials using standardized preparations. Some of those same studies also reported small improvements in cholesterol and triglycerides. The overall evidence is limited and mixed: aloe gel is not a proven treatment for diabetes or high cholesterol, and it is not a replacement for prescribed medication.

The bottom line on oral aloe: the U.S. Food and Drug Administration’s 2002 final rule found aloe not generally recognized as safe and effective as an over-the-counter laxative, because no safety data were submitted for it; non-decolorized whole-leaf extract caused large-intestine tumors in rats in the National Toxicology Program study; the International Agency for Research on Cancer lists whole-leaf extract as possibly carcinogenic to humans (Group 2B); and the long-term safety of swallowing even the gel has not been established.

How People Use It

On the skin (the low-risk option)

• Fresh gel: People slice open a leaf, scoop out the clear inner gel, and spread a thin layer on intact skin — a sunburn, a minor burn after it has cooled, or a patch of dry skin. The yellow layer just under the rind is the latex described above, which is why the gel is taken from the center of the leaf.
• Store-bought gel: products differ in how much aloe they contain (aloe high on the ingredient list means more of it) and in added fragrance or alcohol, which can sting and irritate. People reapply it as needed for comfort.
• Aloe is a home remedy for minor issues. Deep, large, or infected burns and wounds are injuries that hospitals treat; aloe is not a treatment for them.

By mouth: what the rules and research say

• Products labeled "inner-leaf," "decolorized," or "purified" have had most of the aloin filtered out (about 100 times less than in non-decolorized whole-leaf extract); "whole-leaf" products and aloe latex have not. Filtering does not remove every concern — see “Where decolorized gel fits in” above.
• Aloe latex as a laxative: the European Medicines Agency’s 2016 herbal monograph on aloe states that aloe laxatives are not to be used for more than 1 week, and warns that long-term use of stimulant laxatives can impair the function of the bowel and lead to dependence on laxatives. Aloe latex also carries the cancer and electrolyte concerns described above. Gentler, better-studied options exist for constipation.
• Swallowed aloe can add to the blood-sugar-lowering effect of diabetes medicines, and the potassium loss from aloe latex is a danger with diuretics (“water pills”) and digoxin (see the interaction list below). Guo and Mei’s 2016 toxicity review links swallowing aloe preparations with diarrhea, low potassium (hypokalemia), dark staining of the colon lining (pseudomelanosis coli) and kidney failure.

Safety & Cautions

Topical gel

Aloe gel on the skin is generally well tolerated. The main issue is an occasional allergic skin reaction (redness, itching, rash). Some people do a quick patch test — a dab on the inner forearm, checked a day later — before spreading it over a large area, particularly those with sensitive skin or known plant allergies.

Oral latex and whole-leaf

This is where the real cautions live:

• Immediate effects: cramping, abdominal pain, and diarrhea. Repeated use can cause loss of electrolytes — especially potassium — and harmless-but-telling dark pigmentation of the colon lining (pseudomelanosis coli).
• Pregnancy and breastfeeding: the European Medicines Agency’s 2016 aloe monograph lists pregnancy and breastfeeding as contraindications (situations in which the medicine is not to be used). Its strong laxative action could stimulate the uterus and raise the risk of premature labor or miscarriage, and anthraquinones may pass into breast milk and cause diarrhea in a nursing infant.
• Children: the same monograph lists children under 12 years of age as a contraindication.
• Bowel conditions: the monograph also lists as contraindications a blocked or narrowed bowel, appendicitis, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, abdominal pain of unknown cause, and severe dehydration.
• The cancer concern from animal studies applies to ingested whole-leaf / non-decolorized aloe, not to gel used on the skin.

Medication interactions (oral aloe)

• Diuretics ("water pills"): combining them with aloe latex can drop potassium dangerously low, because both can deplete potassium.
• Digoxin (a heart medicine): low potassium from aloe latex can make digoxin more dangerous; the European Medicines Agency monograph notes that low potassium strengthens the action of heart glycosides such as digoxin.
• Other oral medications: aloe latex speeds things through the gut and may reduce how well other medicines are absorbed, lowering their effect.
• Diabetes medicines: oral aloe gel may add to their blood-sugar-lowering effect, raising the risk of hypoglycemia (low blood sugar).
• Other stimulant laxatives: stacking them with aloe latex worsens diarrhea and potassium loss.

The Bottom Line

Aloe is two stories in one plant. As a topical gel for minor burns, sunburn, and dry or irritated skin, it is a widely used, low-risk home remedy — modest evidence, easy to use, and gentle, with an occasional skin allergy as the main reported problem. Oral aloe is a different story. The latex is a harsh stimulant laxative that the U.S. Food and Drug Administration removed from over-the-counter products for lack of safety data, and ingested whole-leaf aloe carries a real cancer signal from animal studies (International Agency for Research on Cancer Group 2B). Most of the support for aloe concerns the gel on the skin. For aloe by mouth, the European Medicines Agency limits aloe laxatives to 1 week and lists pregnancy, breastfeeding, children under 12 and several bowel conditions as contraindications, and even decolorized extract has shown genetic toxicity in laboratory tests.

Key Research Papers

1. Maenthaisong R, Chaiyakunapruk N, Niruntraporn S, Kongkaew C. The efficacy of aloe vera used for burn wound healing: a systematic review. Burns. 2007;33(6):713–718. — Pooled controlled trials suggest topical aloe may shorten healing of first- and second-degree burns, but the trials were small and low-quality, so the conclusion is tentative. — doi:10.1016/j.burns.2006.10.384
2. Surjushe A, Vasani R, Saple DG. Aloe vera: a short review. Indian J Dermatol. 2008;53(4):163–166. — A dermatology overview of aloe's skin uses that emphasizes promising traditional applications alongside a real shortage of controlled efficacy data. — doi:10.4103/0019-5154.44785
3. Boudreau MD, Mellick PW, Olson GR, et al. Clear evidence of carcinogenic activity by a whole-leaf extract of Aloe barbadensis Miller (aloe vera) in F344/N rats. Toxicol Sci. 2013;131(1):26–39. — The National Toxicology Program study showing that non-decolorized whole-leaf aloe in drinking water caused large-intestine tumors in rats ("clear evidence of carcinogenic activity"). — doi:10.1093/toxsci/kfs275
4. Suksomboon N, Poolsup N, Punthanitisarn S. Effect of Aloe vera on glycaemic control in prediabetes and type 2 diabetes: a systematic review and meta-analysis. J Clin Pharm Ther. 2016;41(2):180–188. — In prediabetes oral aloe improved fasting glucose with no effect on HbA1c; in type 2 diabetes it improved HbA1c, with only a marginal fasting-glucose effect. Results were heterogeneous, so the authors called for better trials. — doi:10.1111/jcpt.12382
5. Guo X, Mei N. Aloe vera: a review of toxicity and adverse clinical effects. J Environ Sci Health C. 2016;34(2):77–96. — A safety-focused review documenting the ~100-fold higher aloin in non-decolorized whole-leaf extract, the laxative and electrolyte effects of oral latex, and the colon-tumor findings. — doi:10.1080/10590501.2016.1166826

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Connections

• All Herbs
• Aloe Vera History
• Aloe Vera Benefits
• Wound Healing — aloe's evidence graded within the full repair guide
• Manuka Honey
• Tea Tree
• Turmeric
• Conditions on this site that reference this page: Psoriasis · Gum Disease · ENT (Ear, Nose & Throat) · Prediabetes · Endocrinology · Crohn's Disease · Gastroesophageal Reflux Disease (GERD) · Microscopic Colitis

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