If any one plant can be called America’s folk remedy, it’s aloe vera. An aloe plant on the windowsill is nearly as common as salt and pepper shakers on the kitchen table, and it’s a rare American household where a burn hasn’t been treated at least once with the cooling gel from a fresh aloe leaf. If you spend a lot of time working crossword puzzles or playing scrabble, you probably encounter the word often: few others consist of seventy-five percent vowels.
For countless Americans, myself included, aloe vera has been the first encounter with a medicinal herb. As teenagers in coastal Maine, my friends and I would head for the beach on a warm, early spring day to start renewing our suntans, and after frying our pallid winter skin, we’d rub aloe gel on each other’s blistered backs.
Aloes are perennial succulents primarily native to Africa. Of more than 360 Aloe species, 130 are South African natives, but most species have been introduced in other parts of the world. Despite their superficial resemblance to cactus, aloes are actually members of the lily family. The most familiar species, A. vera, is unusual among plants in that its complete botanical name is also its common name. Because of its common use in treating burns and wounds, it’s is also called burn plant, first-aid plant, and medicine plant. The Mexican century plant, though sometimes called American aloe, is an Agave, not an Aloe species. The name aloe comes from the Greek name for the plant, which in turn was inherited from one of its ancient Arabic names, alloeh. Vera is Latin for “true”.
The original name given to the plant by the botanist Linnaeus was A. perfoliata, which he later amended to A. p. var. vera. In the mid-1700s, taxonomist Philip Miller named it A. barbadensis, probably referring to its proliferation in Barbados. A few years earlier, N. L. Burman had independently given it the now-familiar name A. vera. Burman’s publication apparently went unnoticed at first, and in the early 1800s, Webb and Berthelot also published the name A. vera. Because the earliest known publication of a valid botanical name has priority over subsequently published names, taxonomists eventually reverted to Miller’s A. barbadensis. That name appeared in Hortus Third (Macmillan, 1976), which quickly became a popular taxonomic reference among horticulturists. Since its publication, however, Burman’s original work has resurfaced, and aloe vera is once again Aloe vera.
Growing Aloe Vera
Unless your predilection for aloe requires large quantities of the gel, your best bet is to use that aloe plant on the windowsill. Happily, aloe is one of those plants that’s easy to grow because it practically thrives on neglect. (It’s been said that if you can’t keep an aloe plant alive, you may as well buy plastic plants.) However, as a tropical or subtropical native, aloe vera can’t tolerate temperatures below about 40°F: if your potted aloe happens to be outside when the first fall frost hits, it’ll soon be nothing more than a blackened, oozing mass of dead tissue.
My plants do well in a bright window out of direct, burning sunlight. The soil should be well-drained and porous—a coarse, sandy potting soil that’s not too rich seems to suit aloe best. Overwatering and poor drainage are the greatest threats to this plant
If you leave an aloe undisturbed in a slightly oversized pot, it will soon produce suckers which, when they’re a couple of inches tall, can easily be separated from the main plant and replanted. You can also cut off an overlong stalk and simply plant it in a pot: it will root readily.
The leaves can be cut with a sharp knife at the base of the plant, wrapped in cellophane, and stored for a week or two at 50° to 70°F. (The refrigerator is too cool.) Better yet, use the leaves fresh.
Aloe in History
The earliest known reference to aloe is its depiction in a cave painting from a remote region near the Orange River in South Africa. Although we don’t know all of its uses, there’s no doubt that the plant played an important role in the lives of Stone-Age South Africans. It’s easy to imagine a group of them sitting around a campfire after a successful hunt. A hungry child reaches for a sizzling piece of roasted wildebeest and is accidentally burned by the fire, and a concerned adult immediately steps off into the bush, breaks off an aloe leaf, and dresses the burn with the soothing gel.
The earliest recorded use of aloe comes from the fourth century B.C., at which time the plant was called mussabbar in Arabic and was used for relieving inflammation and pain in all parts of the body.
Perhaps due to the inevitable changes in meaning through translation of the Bible from Hebrew to Greek to English, it appears that the aloes referred to in the Old Testament are not the same as those of the New Testament. The plants alluded to in the Old Testament may have been one or more of the lignum aloes such as eaglewood (Aquilaria agallocha), a tree native to Indo-Malaysia that grows to 120 feet tall. Some scholars consider the Old Testament aloe to be sandalwood (a Santalum species) while others argue that it’s cedar of Lebanon (Cedrus libani). If only Linnaeus had been an ancient Greek rather than a post-Renaissance Swede, the true identity of the biblical aloes might have been sorted out two millennia ago.
Scholars agree more closely that the aloe of the New Testament is Aloe succotrina, a true aloe which was brought by Nicodemus to embalm the body of Christ and which the ancient Egyptians used in their embalming arts. A. succotrina is native to the island of Socotra, off the east coast of Africa near the mouth of the Red Sea, and is similar to aloe vera except that its flowers are red (rather than the orange or yellow of A. vera flowers) and the marginal spines along its leaves are dark purple—hence its former name, A. purpurascens. A. succotrina is cultivated for sale in Europe but is not currently available in the United States.
The Greeks of the fourth century B.C. also knew aloe as a product of the island of Socotra, and they obviously considered it invaluable. Upon conquering the king of the Persians and the king of the Indies, Alexander the Great was advised by Aristotle to seek possession of the island that produced aloe. Alexander removed the original inhabitants of Socotra and replaced them with Greeks whom he enjoined to preserve and protect the highly valued aloes.
For many centuries, aloe reached Europe via the Red Sea and Alexandria, but after a route to India was navigated around the Cape of Good Hope, trade patterns changed. By the end of the seventeenth century, England’s East India Company was making direct deals with the King of Socotra. At that time, aloe was valued less for the clear leaf gel than for the resinous yellow exudate of the leaf dermal cells—now known as drug aloe—which was used as a laxative.
Healing with Aloe
The seeds of the current interest in aloe vera were sown in the mid-1930s when researchers enthusiastically reported quick and complete healing of skin burns caused by x-rays and ultraviolet and gamma rays. This information lay relatively dormant for a few decades, however. In 1966, Gertrude B. Foster mentioned the herb in her classic book, Herbs for Every Garden, noting that it was popular in the tropics and as a house plant in temperate countries. This brought the herb back into the public limelight, but commercial attention didn’t focus on aloe vera until sometime in the 1970s. Since then, its popularity has exploded.
As mentioned above, two major products are derived from the leaves of Aloe species. The clear gel that forms naturally in the hollow interior of the leaf is the familiar product used to relieve burns and wounds, whereas specialized resin canal cells in the thick leaf epidermis produce a yellow, bitter juice that is the source of the laxative drug aloe. Although they share certain components, these two products are distinctly different and should not be confused.
Drug aloe. After the leaves have been cut at the base to release the yellow juice, the juice is heated to evaporate the water, and the dark brown mass that remains is drug aloe. Commercial aloin is a refined form of drug aloe that contains high concentrations of barbaloin, the main active laxative compound.
As in ancient times, drug aloe and its derivatives are used extensively today as active ingredients in commercial laxative preparations, most often in combination with other botanical laxatives such as buckthorn bark, cascara sagrada bark, and senna leaves or pods. In Germany, concentrated extracts of dried aloe leaves serve as specialized laxatives in rectal surgery and the treatment of hemorrhoids.
Despite its widespread commercial use, drug aloe and aloin are considered the least desirable of the plant laxatives for home health care. Besides being extremely bitter, they produce cramping and irritation in the digestive tract. Overdose or other misuse can result in abdominal pain, gastrointestinal bleeding, and possibly kidney disorders. Products containing drug aloe or aloin cannot be used by pregnant or nursing women because they stimulate the uterus (which may bring on premature labor) and because they pass readily into the mother’s milk, causing gastrointestinal distress in the nursing infant.
Aloe gel. The gooey tissue in the center of the aloe leaf contains a mucilaginous gel which is prepared commercially by numerous methods, some of them patented or proprietary processes. Most involve pressing, but some entail solvent extraction. According to Albert Leung, a natural products chemist, properties of commercial gel products produced by solvent extraction vary greatly and generally are not representative of aloe gel squeezed from a fresh aloe leaf.
Aloe gel is perhaps the most widely recognized domestic herbal remedy in the United States, used to relieve thermal burn and sunburn and to promote wound healing and also as a skin moisturizer and softener. Everyone who uses it seems convinced that it works, and its use for the same purposes over a few millennia tends to confirm that assumption. However, scientific confirmation of aloe’s properties is not a simple matter and certainly is not definitive.
The conventional pharmaceutical approach to the question “How does it work?” is to determine which individual chemical component of the plant contributes its primary activity. This opens the door to commercial extraction and refinement—processes that can be patented. In regard to aloe, however, this magic-bullet method of investigation hasn’t yet provided clear-cut answers. Aloe vera gel comprises more than seventy-five chemical compounds. Among them are several polysaccharides—sugars that are often mucilaginous when highly concentrated in plant tissue. Other constituents include steroids, organic acids, enzymes, antibiotic agents, amino acids, and minerals. One enzyme found in aloe gel has been suggested as the primary antithermic agent in Aloe species, the component that may be responsible for the plant’s ability to heal burns. However, although numerous recent studies have focused on the physiological mechanisms of aloe, to date no definitive answers have emerged.
Since the first clinical success with the gel in the mid-1930s, other trials have appeared to give similar, positive results. However, evidence from those experiments and from numerous favorable case histories is not conclusive in scientific terms because much of the work suffered from poor experimental design and insufficiently large test samples. With the recent resurgence of public interest in aloe vera gel, new research has confirmed the likelihood of useful physiological effects, but physiological properties ascribed to the gel still can’t be ascribed to specific components.
Researchers at Tokyo Women’s Medical College in Japan have shown that certain lectins (a type of protein) in aloe gel may stimulate the immune system to augment production of natural killer cells in the blood. Other studies have shown that aloe has anti-inflammatory, anti-ulcer (inhibiting gastric secretion and gastric lesions), and antitumor properties. A research group at the University of Texas Health Science Center in San Antonio has studied the effects of aloe extracts on normal and tumor cells in humans. Although aloe probably will not emerge as a new cancer drug, such experiments provide further information on the possible mechanisms of aloe gel in healing wounds and burns.
A review of the medical literature by a group at the University of Texas in Galveston concluded that aloe gel clearly promotes wound healing and is of therapeutic value in thermal injuries and a wide variety of soft-tissue injuries. It prevents progressive skin damage following burn injuries, frostbite, and electrical burns. The review suggests that aloe gel penetrates injured tissue, relieves pain, is anti-inflammatory, and dilates capillaries to increase blood supply to the injury. Ultimately, it increases tensile strength at the wound site and enhances cross-linking and interactions with substances that naturally occupy the space between cells in the body. All of these activities promote wound healing.
Aloe is an ingredient of hundreds if not thousands of cosmetic products, and many manufacturers of such products make anti-aging claims. According to Ivan E. Danhof of North Texas Research Laboratory in Grande Prairie, Texas, many such claims actually refer to moisturizing effects which, while diminishing undesirable surface defects and blemishes temporarily, do nothing to change actual dermal losses as skin ages. However, Danhof’s review of the subject indicates that aloe vera extracts do have the potential—as yet unproven—to stimulate synthesis of collagen and elastin fibers and thus reverse the degenerative skin changes associated with aging.
For every two studies that indicate a positive benefit from aloe, one study can be found with negative results. The balance of scientific evidence, however, leans toward confirmation of the plant’s effectiveness, especially in home first aid. In his popular book Natural Health, Natural Medicine (Houghton Mifflin, 1990), Dr. Andrew Weil suggests that fresh aloe gel applied directly to the skin provides immediate, soothing relief for sunburn, thermal burns, and general skin irritation or inflammation. He cautions, however, that commercial products which boast of their aloe content may not contain sufficient amounts to be effective.
Aloe vera juice products are widely available for internal use and are considered helpful in healing many types of gastrointestinal irritation. According to Dr. Leung, who has evaluated aloe gel products extensively, commercial aloe vera “juice” is normally produced by diluting aloe vera gel with water and adding citric acid and/or other preservatives. It is also sometimes mixed with other herbal extracts or fruit juices. Despite label claims of purity, Dr. Leung points out that the juice may contain only a very small percentage of aloe vera gel. Dr. Weil warns further that ingesting too much aloe juice can act as an irritant laxative. He suggests no more than one teaspoonful should be taken at a time, and only after meals.
Aloe products are available in liquid and solid forms. The most popular liquids are concentrates of various strengths; “spray-dried” aloe vera is the most popular solid product. Although commercial liquid concentrates are usually genuine, Dr. Leung suggests that the higher the concentration of aloe, the more degradation it has undergone. He also warns that despite claims that solid products are 200x concentrates of pure aloe gel, most contain large proportions of carriers such as gums (acacia gum, guar gum, and locust bean gum), lactose, and hydrolyzed starch. Product qualities vary greatly among suppliers, and distinguishing good products from bad is not always easy, even for scientists. Read the label—and caveat emptor.
Few plants can claim a 4000-year history of use for essentially the same purposes, and few plants are as easy to grow and use as aloe. If you are like most people, you take the plant for granted, but it’s become common knowledge that if you take care of your aloe plant, it will help take care of you.
Steven Foster is an herbalist, author, researcher, and consultant in Fayetteville, Arkansas.