Asphodelaceae

Aloe vera

Aloe vera · Barbados aloe

Mixed Caution

Part used: leaflatex
Native range: Probably the Arabian peninsula; a cultigen, spread and naturalised throughout the tropics
Morphology: A stemless succulent forming rosettes of thick grey-green toothed leaves, each containing clear inner gel and, just under the rind, a bitter yellow latex. The two are different substances with different effects.
Also known as: Aloe barbadensis

What is in it

anthraquinone glycosides aloin, barbaloin

polysaccharides acemannan

glycoproteins

Evidence

Topical gel has modest evidence in minor burns and some skin conditions, and notably failed to help radiation dermatitis in trials. Oral use for constipation works through the latex and is effective and unwise. Oral gel for diabetes and irritable bowel has small inconsistent studies.

Safety

The distinction between gel and latex is the whole safety story. The yellow latex is a stimulant laxative containing anthraquinones; it causes cramping and electrolyte loss, and prolonged use damages the bowel. Non-decolourised whole-leaf extract has been classified as possibly carcinogenic to humans by the IARC after rodent studies, and the US banned aloe as an over-the-counter laxative ingredient in 2002 for lack of safety data.

Interactions: Potassium loss compounds digoxin toxicity and diuretics; May lower blood glucose

Regulatory: Removed from over-the-counter laxatives in the US. Permitted topically and in decolourised forms as a food and listed ingredient.

How the traditions classify it

Galenic Hot and dry, and strongly purgative — the classical use is the latex, not the gel.

Ayurvedic Kumari — bitter and cooling, used for the liver and for the skin.

Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.

Historical use

Recorded in Egyptian, Greek and Islamic sources, traded as a valuable purgative drug for two thousand years. The topical use of the gel is well attested but was historically secondary to the purgative use of the latex.

Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.

Worth knowing

Aloe is two different medicines in one leaf, and almost nobody buying it knows which one they have.

The clear inner gel is mostly water and polysaccharide, is benign, and is what people picture. The bitter yellow latex sitting immediately under the rind is an anthraquinone purgative, and it is what the classical sources meant by aloes — a valuable and drastic drug, not a skin soother.

Commercial processing separates them and decolourises the product to remove the aloin. Whole-leaf preparations that skip that step are the ones the toxicology concerns attach to. Cutting a leaf at home gives you both, in unknown proportion.

Nomenclature verified against GBIF backbone taxonomy.