Aloe vera ( Aloe vera )

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The Longwood Herbal Task Force
(http://www.mcp.edu/herbal/default.htm) and
The Center for Holistic Pediatric Education and Research
(http://www.childrenshospital.org/holistic/)
Aloe vera (Aloe vera)
Kathi J. Kemper, MD, MPH and Victoria Chiou, BA
Principal Proposed Uses: Topical treatment of burns, abrasions, and canker sores; laxative
Other Proposed Uses: Experimental treatment of ulcers and HIV; immunostimulant
Overview
Numerous aloe species around the world are used for conditions ranging from dermatitis
to cancer. Aloe gel’s greatest use is as a skin salve and vulnerary for minor burns, abrasions,
canker sores and other epithelial injuries. There is growing experimental evidence for its use as an
antiviral, an ulcer remedy and an adjuvant cancer treatment due to its immune modulating effects.
Aloe latex is a potent laxative that can cause severe cramping and diarrhea; it should not be used
during pregnancy, lactation or by children less than 12 years old. Allergic reactions to aloe have
been reported. Long-term use of anthraquinone laxatives may result in laxative dependence,
pseudomelanosis coli, dehydration, potassium depletion, weakness, and arrhythmias. Aloe should
not be used as a laxative by persons with undiagnosed abdominal pain, appendicitis, or intestinal
obstruction.
Historical and Popular Uses
Ancient Egyptian papyrus and Mesopotamian clay tablets describe aloe as useful in curing
infections, treating skin problems and as a laxative1. Cleopatra was said to include aloe cream in
her beauty regimen2. Aloe was used by Hippocrates and Arab physicians, and was carried to the
Western Hemisphere by Spanish explorers. Legend has it that Alexander the Great captured the
island of Socotra in the Indian Ocean to secure its aloe supplies to treat his wounded soldiers3.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 1
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

Aloe is also popular in both traditional Chinese and Ayurvedic medicine. The Chinese
describe aloe’s skin and the inner lining of its leaves as a cold, bitter remedy which is downward
draining and used to clear constipation due to accumulation of heat (fire)4; the gel is considered
cool and moist. In Ayurvedic medicine, the traditional medicine of India, aloe is used internally as
a laxative, antihelminthic, hemorrhoid remedy, and uterine stimulant (menstrual regulator); it is
used topically, often in combination with licorice root, to treat eczema or psoriasis. In Arabian
medicine, the fresh gel is rubbed on the forehead as a headache remedy or rubbed on the body to
cool it in case of fever, as well as being used for wound healing, conjunctivitis, and as a
disinfectant and laxative5.
Today aloe vera gel is an active ingredient in hundreds of skin lotions, sun blocks and
cosmetics6. The gel’s use in cosmetics has been boosted by claims that it has similar anti-aging
effects to vitamin A derivatives7. Aloe first gained popularity in the United States in the 1930’s
with reports of its success in treating X-ray burns8,9,10. Recently, aloe extracts have been used to
treat canker sores, stomach ulcers and even AIDS. Some natural health enthusiasts promote aloe
gel as a cleansing juice11. Some naturopaths promote aloe juice as a way to prevent and treat
renal stones12. Many mothers keep a plant handy in the kitchen where it readily thrives in bright
sunlight with little care13. When faced with a minor burn, a fresh leaf can be cut and the gel of the
inner leaf applied directly to the burn immediately after the injury14. The inner leaf lining of the
plant is used as a potent natural laxative. In a 1990 survey of members of a health maintenance
organization, aloe vera was used by 64%; of these, 91% believed it had been helpful15. Aloe is
also an ingredient in Compound Benzoin tincture16.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 2
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

Botany
Medicinal species: Aloe vera, A. barbadensis (Curacao or Barbados aloe), A. vulgaris, A.
arborescens, A. ferox (Cape aloe), A. perryi (Socotrine or Zanzibar aloe). There are over
300 species of aloe, most of which are native to South Africa, Madagascar and Arabia5.
The different species have somewhat different concentrations of active ingredients17,18.
Common names: Aloe, aloe capensis, aloe spicata, aloe vera, Barbados aloe, Cape aloe,
chirukattali (India), Curacao aloe, Ghai kunwar (India), Ghikumar (India), Indian aloes,
kumari (Sanskrit), laloi (Haiti), lohoi (Vietnam), luhui (Chinese), nohwa (Korean), rokai
(Japanese), sabilla (Cuba), Socotrine aloe, subr (Arabic), Zanzibar aloe5,19,20. The name
aloe is derived from the Arabic word alloeh meaning a shining bitter substance16. NOTE:
“aloes” refers to the latex leaf lining used as a laxative; aloe wood (mentioned in the Bible)
is an entirely different plant.
Botanical family: Liliaceae
Plant description: The aloe plant has long (up to 20 inches long and 5 inches wide), triangular,
fleshy leaves that have spikes along the edges. The fresh parenchymal gel from the center
of the leaf is clear; this part is sometimes dried to form aloe vera concentrate or diluted
with water to create aloe juice products. The sticky latex liquid is derived from the
yellowish green pericyclic tubules that line the leaf (rind); this is the part that yields
laxative anthraquinones21,22. The flowers (not used medicinally) are yellow.
Where it’s grown: Aloes are indigenous to South Africa and South America, but are now
cultivated worldwide except in tundra, deserts and rain forests. In the US aloe is
commercially cultivated in southern Texas23. It takes approximately four years to reach
maturity and has a lifespan of about 12 years.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 3
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

Biochemistry
AloeVera: Potentially Active Chemical Constituents
From the gel:
• Polysaccharides: glucomannan and acemannan
• Other: carboxypeptidase, magnesium, zinc, calcium, glucose, cholesterol, salicylic acid,
prostaglandin precursors (gamma-linolenic acid [GLA]), vitamins A, C, E, lignins, saponins,
plant sterols and amino acids3,24
From the latex leaf lining:
• Anthraquinone glycosides: aloin, aloe-emodin, barbaloin (15% -30%)25
The gel or mucilage obtained from the flesh of the leaf contains quite different compounds
from the bitter latex extracted from the leaf lining26. Aloe gel is 99% water with a pH of 4.5 and
is a common ingredient in many non-prescription skin salves. The gel contains an emollient
polysaccharide, glucomannan. It is a good moisturizer, which accounts for its use in many
cosmetics27. Acemannan, the major carbohydrate fraction in the gel, is a water-soluble long chain
mannose polymer which accelerates wound healing, modulates immune function (particularly
macrophage activation and production of cytokines) and demonstrates antineoplastic and antiviral
effects28,29,30. The gel also contains bradykininase, an anti-inflammatory31, magnesium
lactate, which helps prevent itching, and salicylic acid and other antiprostaglandin compounds
which relieve inflammation.
The leaf lining (latex, resin or sap) contains anthraquinone glycosides (aloin, aloe-emodin
and barbaloin) that are potent stimulant laxatives. These water soluble glycosides are split by
intestinal bacteria into aglycones which effect the laxative action. The laxative effect from aloe is
stronger than from any other herb, including senna, cascara or rhubarb root; it also has more
severe side effects such as cramping, diarrhea, and nausea32. For medicinal use, the leaf lining is
dried and the residue is used as an herbal laxative. The products are usually taken at bedtime.
They are poorly absorbed after oral administration, but moderately well absorbed after bacterial
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 4
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

hydrolysis. They are eliminated in the urine, bile, feces and breast milk. They turn alkaline urine
red33. Most herbalists recommend that they be avoided during pregnancy due to the risk of
stimulating uterine contractions and also avoided during lactation due to the risk of excretion in
breast milk34. Aloe is seldom recommended as a first choice among laxative preparations due to
the severe cramping and nausea associated with its use.
Experimental Studies
Aloe Vera: Potential Clinical Benefits
1. Cardiovascular: none
2. Pulmonary: none
3. Renal and electrolyte balance: none
4. Gastrointestinal/hepatic: Stimulant laxative (leaf lining); gastric and duodenal ulcers (gel);
inflammatory bowel disease (gel, experimental use)
5. Neuropsychiatric: none
6. Endocrine: Hypoglycemic (gel)
7. Hematologic: none
8. Rheumatologic: none
9. Reproductive: Emmenagogue (leaf lining, traditional use)
10. Immune modulation: Immunostimulant, anti-inflammatory (gel)
11. Antimicrobial: Antibacterial, antiviral, antifungal (gel)
12. Antineoplastic: Antitumor, attenuation of adverse effects of cancer therapies (gel)
13. Antioxidant: none
14. Skin and mucus membranes: Vulnerary (wound healing), psoriasis remedy (gel)
15. Other/miscellaneous: none
1.
Cardiovascular: none
2.
Pulmonary: none
3.
Renal and electrolyte balance: none
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 5
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

4.
Gastrointestinal/hepatic: Stimulant laxative (leaf lining), gastric and duodenal ulcers
(gel), inflammatory bowel disease (gel, experimental use)
a. Laxative (leaf lining): Barbaloin, or aloin, derived from the inner sheath cells of the
leaves, is a bitter, yellow laxative.
i.
In vitro data: Aloe affects the sodium/potassium pump and chloride channels at the
colonic membrane37,38.
ii. Animal data: Aloe’s anthraquinones enhance intestinal propulsion and water secretion
in mice39.
iii. Humans data: The anthraquinones found in the latex stimulate chloride and water
secretion into the large intestine, inhibit its reabsorption and stimulate peristalsis33,40.
Typical onset of action is 6 –12 hours after a single oral dose; this can be accompanied
by severe cramping, bloody diarrhea and nausea. Randomized controlled trials have
documented its potency as a cathartic in chronically constipated adults41.
b. Gastric and duodenal ulcers (gel)42.
i.
In vitro data: Aloe-emodin inhibits growth of Helicobacter pylori in a dose-dependent
fashion43.
ii. Animal data: Aloe vera inhibits gastric acid secretion in mice and rats and has
protective effects against gastric mucosal damage in rats44. Pretreatment with aloe
vera extract reduced aspirin-induced gastric mucosal injury by 70% in experimental
rats45. Aloe extracts also suppressed the ulcerogenic effects of stress in experimental
rats46.
iii. Human data: A 1960’s pilot study of 18 adults indicated that aloe vera gel might be
helpful in treating patients with duodenal ulcers. However, there was not a comparison
group of untreated patients, nor were details given on other remedies the patients
might have been using47.
c. Inflammatory bowel disease (gel). Acemannan is under consideration as an experimental
remedy for inflammatory bowel disease35,36; no experimental data.
5. Neuropsychiatric: none
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 6
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

6. Endocrine: Hypoglycemic (gel)
i.
In vitro data: none
ii. Animal data: Aloe gel caused low blood sugar in diabetic laboratory mice in some
studies48,49. It lowered blood sugar in both diabetic and normal mice in another study50,
but had no impact on blood sugar levels in diabetic or normal animals in other
studies51,52.
iii. Human data: Nearly half of diabetic patients surveyed in Texas reported using aloe vera
or other herbal remedies as complementary therapies for their diabetes53. Aloe gel
appeared to enhance the hypoglycemic effect of glibenclamide when given orally to
diabetic patients in doses of 1 – 2 tablespoons twice daily54,55. There are no reported
randomized controlled trials comparing aloe to any oral hypoglycemic agent or insulin in
treating human diabetics. There are no studies evaluating the potential toxicity of taking
aloe products orally by patients requiring medical therapy for glycemic control.
7. Hematologic: none
8. Rheumatologic: none
9. Reproductive: Emmenagogue (leaf lining; traditional use)
i.
In vitro data: none
ii. Animal data: Aloe extracts at doses of 100 – 150 mg/kg had no abortifacient effects in
pregnant rats20.
iii. Human data: none
10. Immune modulation: Immunostimulant and anti-inflammatory (gel)56,57
i. In vitro data: Acemannan increases monocyte and macrophage activity and cytotoxicity,
stimulates killer T-cells and enhances macrophage candidacidal activity in
vitro29,58,59,60,61,62. Acemannan enhances macrophage release of interleukin–1 (LI-1),
interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and interferon gamma (INF-γ)
in a dose-dependent fashion29,63.
On the other hand, aloe extracts block prostaglandin and thromboxane production
from arachidonic acid, reducing inflammation64,65,66.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 7
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

ii. Animal data: Acetylated mannans from aloe injected subcutaneously into
myelosuppressed mice stimulated an increase in white blood cell counts, splenic cellularity,
and absolute numbers of neutrophils, lymphocytes and monocytes67,68,69,70,71,72. Aloe
extracts reduced the production of interleukin-10 following exposure to ultraviolet
radiation, reducing the suppression of delayed type hypersensitivity73,74,75.
Aloe enhanced the anti-inflammatory activity of hydrocortisone while blocking its
wound healing inhibition when applied topically to mice76,77. Aloe extracts had
antiinflammatory effects equivalent to hydrocortisone in the mouse ear model; although
hydrocortisone administration was associated with a decrease in thymus weight, the aloe
extracts had no such effect78. In rat paw models, fresh aloe gel showed significant anti-
inflammatory activity and increased wound strength79,80. Rats with adjuvant-induced
arthritis exhibited fewer symptoms when treated with a topical preparation containing
aloe81. Aloe extracts also blocked mast cell inflammatory responses to antigen-antibody
complexes82,83.
iii. Human data: In a case series of 14 HIV-1+ patients who were prescribed 800 mg/day of
acemannan, there was a significant increase in the number of circulating monocyte and
macrophages which mirrored clinical improvements84. In a pilot study in HIV-infected
persons acemannan increased the number of white blood cells and improved symptoms85.
Aloe extracts also increased phagocytosis in asthmatic adults86.
There are no reported trials evaluating the effectiveness of aloe as a systemic anti-
inflammatory agent in humans.
11. Antimicrobial: Antibacterial, antiviral, antifungal (gel)
a. Antibacterial
i.
In vitro data: Aloe gel is bacteriostatic or bactericidal against a variety of common
wound-infecting bacteria in vitro: Staphylococcus aureus, Streptococcus pyogenes,
Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa, E. coli,
Salmonella typhosa and Mycobacterium tuberculosis64,87. Aloe-emodin also inhibits
the growth of Helicobacter pylori in a dose-dependent fashion43.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 8
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

ii. Animal data: none
iii. Human data: none
b. Antiviral
i.
In vitro data: Acemannan acts alone and synergistically with azidothymidine (AZT)
and acyclovir to block reproduction of Herpes and the AIDS virus88,89,90.
ii. Animal data: none
iii. Human data: Acemannan hydrogel (trade name is Carrisyn) is currently under
investigation as a treatment for persons infected with HIV; doses are up to 250
milligrams QID (about one quart of raw aloe gel daily)13,85. In pilot randomized
controlled trials of HIV+ adults with low CD4 counts, aloe did not contribute
significantly to therapy with ZDV or ddI in terms of effects on CD4 counts, p24
antigen levels or viral load91,92.
In a randomized, controlled double blind clinical trial of 60 men suffering from
an initial episode of Herpes simplex infection, those assigned to treatment with an aloe
vera extract (0.5%) in a hydrophilic cream had a significantly faster healing time and a
higher number of healed lesions than the placebo comparison group93.
c. Antifungal
i.
In vitro data: none
ii. Animal data: Aloe extract treatment of guinea pig feet that had been infected with
Trichophyton mentagrophytes resulted in a 70% growth inhibition compared with
untreated animals94.
iii. Human data: none
12. Antineoplastic: Antitumor, attenuation of adverse effects of cancer therapies (gel)
a. Antitumor
i.
In vitro data: Aloin A and B, aloesin and aloeresin were devoid of antitumor activity,
but aloe emodin caused cytostatic and necrotic effects on human K562 leukemia cell
lines95.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 9
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm

ii. Animal data: Acemannan has demonstrated activity against feline leukemia virus and
solid tumors28,96,97,98,99,100,101. For example, among cats with feline leukemia, a
virally-induced disease with a mortality rate of 70% - 100%, a six-week treatment
series with acemannan injections (2 mg/kg per weekly dose) resulted in a 71% survival
rate98.
In a group of laboratory mice implanted with malignant sarcoma cells who
were treated with intraperitoneal injections of acemannan, all the mice in the control
group developed malignant tumors and died within seven weeks, but 40% of the
treated mice survived and showed signs of tumor necrosis and regression28. In rats,
concurrent treatment with aloe extracts inhibited hepatic tumor induction102,103. In a
study of dogs and cats with fibrosarcomas treated with daily injections of acemannan
in combination with surgery and radiation therapy, significant shrinkage of tumors and
increase in necrosis and inflammation were observed99. In another study of 46 dogs
and cats with spontaneous tumors who were treated with acemannan injections, 26
had histopathologic evidence of tumor necrosis and 12 exhibited significant clinical
improvement; soft tissue sarcomas appeared to be particularly susceptible to
treatment97.
iii. Human data: Based on findings from animal studies, aloe research in human cancer
patients is currently in progress. At the University of Texas-Houston Medical School
and Herman Hospital, a Phase I study with injectable aloe for cancer patients is being
conducted. In a preliminary study of 50 patients suffering from lung cancer,
gastrointestinal tract tumors, brain stem gliomas or breast cancer who were treated
with melatonin alone or melatonin plus aloe, those in the combination therapy group
had significantly better one-year survival104
b. Attenuation of adverse effects from cancer therapies (gel). Aloe vera gel has been
recommended to treat radiation-induced dermatitis and mucositis.
i.
In vitro data: See Immune modulation and Skin and mucus membranes: vulnerary.
ii. Animal data: See Immune modulation and Skin and mucus membranes: vulnerary.
Kathi J. Kemper, MD, MPH
Aloe Vera
Page 10
and Victoria Chiou, BA
Revised July 29, 1999
Longwood Herbal Task Force: http://www.mcp.edu/herbal/default.htm