Two basic substances are extracted from the leaves of the cactus-like succulent plant aloe vera (aloe barbadensis MILLER): The so-called gel is derived from the pulp of the leaves and contains carbohydrate polymeres such as glucomannanes or pectic acid.
Aloe latex (aloe juice) is a bitter tasting exudate derived from the rind of the leaf and consists of, among other substances, anthraquinones such as aloin. Gel and latex are not always separated properly, at times causing the presence of anthraquinones in the gel as well (1).
Aloe gel is supposed to be effective externally in treating wounds, minor burns, skin irritations or psoriasis (1,3). Preparations for internal use are offered for constipation, cough, headaches, infectious diseases, rheumatic fever, allergies, ulcers, heart disease, HIV (human immunodeficiency virus) infections and cancer (1,2).
We found five randomised trials with aloe vera. In one study with 49 patients aloe gel did not work any better than gauze soaked in saline for the treatment of pressure ulcers (4). Used as an adjunct to standard wound care in a study with 40 patients it even seemed to interfere negatively with the healing process (5).
When aloe gel was applied externally as preventive treatment in percutaneous radiation therapy in 194 patients with breast cancer, it showed no advantage over placebo in all tested end-points (severity, duration, time to manifestation of radiation dermatitis) (6). A subsequent study with another 73 patients was not able to refute the results: While the authors seem to have noted a delay in the appearance of radiation dermatitis in the subgroup of patients who were treated with high doses of radiation, the effect cannot be attributed to aloe, because a placebo gel was lacking (7).
A Pakistani study consisting of 60 patients revealed astonishing results: A hydrophilic cream containing 0.5% of aloe vera extract, supposedly caused permanent / long-lasting cure after just one month of treatment in 83% of patients who suffered from psoriasis for a mean of 8.5 years, as compared to just 6.6% cure in the control group (3). The fact that the disease did not reappear after even one year in anyone of the "cured" patients, makes us doubt the validity of the study. We did not find any other trial investigating the effects of aloe vera in psoriasis.
Other studies concerning prevention of "atheromatous" heart disease (8) or treatment of solid tumours (9) were of no significance because of methodical shortcomings such as lacking control groups and missing randomisation.
The intake of aloe extracts as a laxative seems reasonable (1). However, the cancerogenic and genotoxic potential of anthraquinone carrying aloe's laxative effect oppose its use (a-t 1999; No. 5: 56; a-t 1996; No. 8: 82). Acute renal failure associated with the anthraquinone-containing extract of cape aloe (aloe ferox MILLER) is reported in a 47-year-old hypertensive South African patient (10).
As from 1st February 1997, the Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM (Federal Institute for Drugs and Medical Devices), limited the laxative use of anthranoid-containing drugs including aloe to a maximally two weeks' treatment (a-t 1996; No. 8: 82), while prohibiting it for any other kind of indication (11).
Summary: The only probably well-founded effect of aloe is the laxative effect of anthraquinone-containing preparations for internal use. However, due to its cancerogenic and genotoxic potential, the use as a laxative cannot be justified. All the other indications are, in our view, not, or not sufficiently proven.