Aloe vera and Aloe barbadensis are the plants commonly referred to as aloe. Aloe barbadensis is a member of the Aloaceae family.  This family of plants is a commonly used botanical medicine and is widely known throughout the western world. Many people have aloe plants in their homes as part of their décor. Others use aloe frequently for skin injuries or include it as a common component in their first aid kits. A piece of the plant can be snipped or cracked off to reveal an exuding gel that has wonderful medicinal properties, including wound healing.
Aloe contains a number of active constituents. The main anthracene derivatives are; anthrone-10-C-glykosyls (aloin A, aloin B, and 7-hydroxyaloin), and 1,8-dihydroxyanthraquinones (aloe-emodin).  Mannose-6-phosphate (acemannan) is a beneficial polysaccharide found in aloe. Acemannan is contained below the skin in Aloe vera leaves, though it is usually not present in juice or gel preparations. Another category of therapeutic constituents found within the Aloe plant include the 2-alkylchromones. These include the aloe resins B, C, and D. Certain flavonoids are also found in this plant.
Actions that are ascribed to aloe:
- cholagogue (stimulates bile flow from the gall bladder)
- choleretic (stimulates production of bile in the liver)
- emmenagogue (stimulate menstrual flow)
- antihelmintic (eliminates parasites)
- vulnerary (wound healing)
- stomachic (induces healthy action of GI)
The effect of aloe on the large intestine is primarily as a cathartic laxative. This action is the result of the anthroquinone glycosides, which are abundant in the latex of the Aloe Vera. These compounds influence motility of the colon and stimulate propulsive contractions resulting in accelerated intestinal passage. In addition, because of the shortened contraction time, a reduction in liquid absorption occurs.  Active chloride secretion is also stimulated, thereby increasing the water and electrolyte content of the stool. The filling pressure of the bowels is also increased, causing stimulation of intestinal peristalsis.
The gel that is found on the market in many skin care products such as burn relief gels is different than whole aloe.  These products contain a yellow latex which is normally found beneath the outer skin of the leaves. The yellow latex is actually the portion that contains the anthroquinone glycosides, which as mentioned, have a laxative action. Furthermore, most preparations are also missing the most active constituent required for aloe’s wound healing ability, acemannan. For this reason, it is usually best to use fresh Aloe, with the exception of just a few special order products.
Aloe has medicinal properties that can be utilized to treat a variety of disorders. Aloe is most widely known for the treatment of skin complaints and for gastrointestinal disorders. However there are also other lesser known conditions for which aloe may be quite useful.
Aloe can be used to treat various dermatologic conditions such as lichen planus, various wounds, and burns. It contains a polysaccharide called glucomannan, which yields anti-inflammatory, antipruritic, and vulnerary properties. [3-6] A controlled clinical trial in patients with full face dermabrasion showed that wound healing was significantly improved when dressings were treated with stabilized Aloe Vera.  Another controlled clinical trial in patients with partial thickness burn wounds was conducted using a dressing treated with either aloe or Vaseline.  Patients receiving the aloe treatment demonstrated a statistically significant improvement in healing time versus those receiving Vaseline therapy.
There is also evidence to support the treatment of psoriasis with aloe. A double-blind, placebo-controlled trial of light to moderately chronic plaque-type psoriasis with PASI (psoriasis area and severity index) scores between 4.8 and 16.7 was carried out using an Aloe Vera extract (0.5% applied topically three times per day, five days per week for a maximum duration of 4 weeks).  The Aloe Vera extract cream successfully treated 25 of 30 patients (83.3%), versus 2 of 30 (6.6%) in the placebo group. Furthermore, the aloe cream did not produce any toxicity or other objective side effects.
Traditionally, aloe has been also been applied as an alternative treatment for chronic constipation. A constituent found in aloe, barbaloin (included in the anthroquinone family), is responsible for producing this laxative effect. A randomized double-blind, placebo-controlled clinical trial of patients with chronic constipation was conducted where participants were administered an encapsulated preparation containing aloe for four weeks.  Improvements in bowel movement frequency, consistency, and reduced dependence on laxatives were observed in the group taking the aloe preparation. An interesting study in patients with chronic hepatitis demonstrated a total effective sGPT-lowering rate of 86.8% following injection therapy with an Aloe Vera extract preparation.  More research is, however, necessary to accurately assess Aloe Vera’s impact upon chronic hepatitis.
Other conditions for which aloe has been found useful include; diabetes, tuberculosis, atheromatous heart disease, and aphthous stomatitis. [12-16] Even more impressive is the wide reaching effect of aloe in the treatment of solid tumors such as cancers of the lung and breast, brain glioblastomas, and GI tract tumors.  The authors of the study suggest that a combination of pineal indole melatonin plus Aloe Vera tincture may produce some therapeutic benefits, concerning the survival and stabilization of disease in patients with advanced solid tumors, for whom no other standard effective therapy is available. Also, patients undergoing higher cumulative doses of radiation therapy may benefit from topical aloe use.  It appears that patients using a particular soap preparation containing aloe observed a protective effect on their skin while undergoing radiation therapy.
Dosages vary according to the preparation is being utilized, and whether the preparation is intended for internal or external use. For internal use, generally 0.1 to 0.3 grams of juice is sufficient for inducing therapeutic effects.  If using whole fresh aloe, small pieces (roughly the size of your pinky finger nail) usually have enough stimulating action for a laxative effect.  For external use, the dosage is not considered important, as long as the afflicted area is properly treated.
Internal aloe administration should not be used if a patient has hemorrhoids, tenesmus, or any irritation of the colon. It should never be administered with gastrointestinal inflammatory conditions such as Ulcerative Colitis, Crohn's disease, gastritis and enteritis. Additionally, aloe should not be taken in cases of intestinal obstruction. Aloe should also be avoided in females prone to menorrhagia (heavy periods) and who are pregnant and/or nursing, as the anthroquinones can be passed through the breast milk.  Patients with renal disorders should not take aloe because of the possibility of an associated kidney inflammation. Children under twelve should never take aloe due to the loss of water and electrolytes, as well as the incidence of abdominal pain of an unknown origin. 
Aloe leaf can increase bowel transit time, reducing the absorption of certain oral drugs. Overuse can also lead to electrolyte depletion, especially potassium loss, which can increase the toxicity of specific pharmaceuticals, including: antiarrhythmic drugs, cardiac glycoside drugs and botanicals (Adonis, Convallaria, Urginea, Helleborus, Strophanthus, Digitalis), thiazide diuretics, corticosteroids, and Glycyrrhiza glabra.  Potassium depletion can result in muscle weakness and increased constipation.  Hemorrhoids can occur with prolonged use. The general recommendation of most medical practitioners is to use aloe internally and no longer than 8-10 consecutive days.
An overdose may cause vomiting, intestinal spasms, kidney inflammation, bloody diarrhea, and mesenteric plexus damage. 
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