Aloe Vera: Traditional Use, Constituents and Evidence

A plant with a very long paper trail

My nan kept an aloe vera on the kitchen windowsill for decades , battered, slightly pot-bound, and almost certainly never repotted once. Every burn, every scrape, every sandfly bite that came through that kitchen got a torn leaf and a smear of gel. She called it "the burn plant." She wasn't wrong that people had been using it that way for a very long time. But the actual chemistry underneath that tradition is a lot more interesting , and a lot more complicated , than the windowsill version suggests.

Aloe barbadensis Miller (the species most of us call aloe vera) has a documented use history stretching back at least 4,000 years. Egyptian papyri reference it. The Greek physician Dioscorides catalogued it in De Materia Medica around 77 CE. Arab traders carried it east. Spanish missionaries introduced it to the Americas in the 16th century. For a succulent from the Arabian Peninsula, it got around.

What's actually inside the leaf

The leaf has two anatomically distinct zones, and this matters enormously when you're reading any research on aloe.

The inner gel; the clear, mucilaginous material, is largely water (roughly 99%), with the remaining fraction made up of polysaccharides (primarily acemannan), glycoproteins, vitamins, minerals, and a range of organic acids. Acemannan is the most studied constituent; it's a long-chain acetylated mannose polymer that shows up repeatedly in immunology and wound-healing literature.

The latex is a different matter entirely. This is the yellow-green layer just beneath the outer rind, and it's where the anthraquinone glycosides, chiefly aloin A and aloin B; sit. These are bitter, strongly laxative compounds. Aloin was historically standardised and sold as a cathartic drug. The TGA classifies products containing aloin and other anthraquinone derivatives as medicines subject to specific listing conditions under the Australian Register of Therapeutic Goods (ARTG); products intended for internal use are subject to different regulatory scrutiny than topical preparations. If you're interested in how standardised extracts work as a regulatory and formulation concept, that distinction between gel and latex illustrates it perfectly.

Beyond acemannan and aloin, the chemical inventory includes:

• Chromones, aloesin and aloeresin, associated with some of the plant's colouring and studied for antioxidant activity
• Lectins and glycoproteins (aloctin A and B)
• Phenolic compounds, including several that are shared across other botanicals in the phytomedicine canon
• Salicylic acid, present in small amounts
• Amino acids, including several the human body classes as essential, for the structural context behind why that matters, see our amino acid glossary entry
• Enzymes including bradykininase, which is proposed to play a role in some of the anti-inflammatory mechanisms researchers have been investigating

It's a dense mixture. And that complexity is part of why the research is so patchy; different studies use different preparations, different species, different ratios of gel to latex, and different methods of processing that can degrade constituents substantially.

Traditional uses across cultures

The ethnobotanical record is striking for its consistency. Topical application to burns, skin irritation, and wounds shows up across Egyptian, Greek, Chinese, Ayurvedic, and Indigenous American traditions with very little cross-contamination of trade routes in the early period. That kind of convergent use in unconnected cultures tends to interest phytomedicine researchers, it's not proof of efficacy, but it's a reasonable signal that something observable was happening.

Internal use varied more widely. In European herbal practice from the Renaissance through to the 19th century, dried aloe latex (Aloe ferox or A. barbadensis) was a mainstream cathartic. It appeared in the British Pharmacopoeia. It was exported from Barbados (hence the old trade name "Barbados aloes"), from the Cape Colony, and from Socotra. By the 20th century, the internal latex preparations had largely fallen out of mainstream pharmaceutical use in Western medicine, though they persist in some traditional systems.

What the research actually shows, and where it stops

Honestly, aloe vera research is in a frustrating middle ground. There's a lot of it, and the quality is uneven.

For topical preparations, the most studied area is radiation dermatitis and minor burn management. A 2016 Cochrane-affiliated systematic review (Dat et al.) found insufficient high-quality evidence to draw firm conclusions on wound healing. A 2019 review published in the Journal of Clinical Medicine examined the gel's proposed mechanisms in more detail at a cellular level; particularly acemannan's interactions with macrophage activation pathways, but noted that most mechanistic work was in vitro or in animal models, with the clinical trial data lagging behind significantly.

Oral aloe gel preparations have been studied in the context of glycaemic markers, oral health, and gut mucosa. I'd flag here that none of this review constitutes a therapeutic claim, describing what researchers have been examining is not the same as stating aloe treats any condition. The literature is observational and mechanistic at this stage for most indications; the randomised controlled trial data is sparse and methodologically varied.

The anthraquinone story is worth a note. The US National Toxicology Program (NTP) published a long-term feeding study in 2013 showing that whole-leaf aloe vera extract; which would contain aloin, caused intestinal tumours in rats at high doses. This led to a reassessment of internal whole-leaf products globally. The European Food Safety Authority (EFSA) subsequently restricted certain internal aloin-containing preparations. In Australia, products for internal use containing anthraquinone glycosides from aloe are subject to TGA assessment; consumers checking the ARTG for any listed medicine should confirm the preparation type (gel vs. whole-leaf) and the level of aloin present.

In terms of bioavailability and pharmacokinetics, acemannan's absorption and systemic distribution in humans is still not fully characterised. Most of the mechanistic work assumes topical or mucoadhesive activity rather than systemic absorption of intact polysaccharide chains.

Regulatory status in Australia

Aloe vera products in Australia sit across a few regulatory categories depending on intended use and formulation. Topical cosmetic preparations are regulated under the Australian Industrial Chemicals Introduction Scheme (AICIS) rather than the TGA. Therapeutic products, anything making a health claim; must be listed or registered on the ARTG. Listed medicines (ARTG "L" prefix) are assessed for safety and quality but not efficacy; registered medicines require demonstrated efficacy data.

Under TGA complementary medicine listing rules, permitted indications for aloe vera ingredients are governed by the permitted indications list for listed medicines. Sponsors cannot simply make any claim they wish, indications must come from the permitted list, and label claims are restricted accordingly. This is worth understanding if you're comparing products: a listed medicine with an aloe vera ingredient has met safety and GMP thresholds (see our note on Good Manufacturing Practice), but the ARTG listing itself is not an endorsement of efficacy by the TGA.

Internal whole-leaf preparations, and certainly aloin-concentrated products, are in a more complex regulatory space. I'd reckon most consumers don't realise the distinction between gel-only and whole-leaf products, and I think the industry has been pretty slow to make that clear on labels. That's my view, for what it's worth.

The chemistry in context

Aloe vera doesn't fit neatly into the single-compound pharmacological model. It's a mixture, and much of the activity that researchers have proposed operates at the level of polysaccharide interactions with cell receptors and membrane surfaces. That puts it in similar territory to other complex botanical preparations, one reason phytomedicine researchers sometimes look across to work on botanical terpene profiles (see our terpene overview for a parallel example of how plant complexity resists reductionist analysis) or to phytomedicine methodology more broadly.

What the 4,000-year paper trail actually tells us is that people have observed something useful enough to keep doing. The chemistry gives us plausible mechanisms. What we're still waiting on; in most areas, is the kind of rigorous, adequately powered clinical trial data that would let those mechanisms be confirmed in humans at meaningful doses. That gap between mechanism and clinical proof is not unique to aloe. It's a consistent feature of botanical medicine research, and worth keeping front of mind when reading any product marketing.

My nan's aloe vera is still alive, actually. I inherited it. It's on the bench in my studio in the Adelaide Hills, even more pot-bound than before. I haven't repotted it either.

Sources

• Listed medicines and permitted indications, Therapeutic Goods Administration (TGA)
• Aloe vera: A short review; Indian Journal of Dermatology (NCBI/NIH)
• Aloe Vera, LiverTox: Clinical and Research Information on Drug-Induced Liver Injury (NCBI/NIH)
• Scientific opinion on the evaluation of the safety of aloe emodin, EFSA Journal

, Naomi Ellison, Botanical & phytomedicine writer