Aloe's healing fame outruns the evidence behind it
Ancient Greeks and Romans dressed wounds with Aloe vera, and it now fills soaps and supplements. Yet clinical evidence is limited. The US Food and Drug Administration ruled in 2002 that aloe was neither safe nor effective as an over-the-counter laxative, and cancer researchers say no aloe product has been shown to prevent or treat cancer.
Aloe is a big genus of succulents, with around 600 accepted species plus many unresolved names and hybrids. Most grow as rosettes of thick, fleshy leaves in shades from grey to bright green, sometimes striped or mottled, and send up leafless stalks of dangling tubular flowers in yellow, orange, pink or red. Some South African species grow into trees. Wild aloes grow across tropical and southern Africa, on Madagascar and other Indian Ocean islands, in Arabia and in India, and people have spread them much further.
Its name may come from an Arabic word for a bitter, shiny substance, or from a Hebrew plural. Classification has shifted repeatedly: aloes have been filed under the lily family and a family of their own, and now sit in Asphodelaceae. The so-called American aloe is actually Agave americana, which belongs to a different family altogether. From 2010 onward, molecular studies showed the genus was not a single natural lineage, and in 2014 John Charles Manning and colleagues split it into six genera, including tree-forming Aloidendron.
Only a handful of species had traditional medicinal roles, chiefly Aloe vera, A. ferox and A. perryi. In the Middle Ages the yellow sap inside the leaves was prized as a purgative. Modern assessments are cautious. Applied to the skin, aloe may help some conditions but can cause irritation or allergy. Taken by mouth as a supplement, it has been linked to diarrhoea, muscle weakness and heart effects, and it is not an approved drug. The International Agency for Research on Cancer lists aloe leaf extract as a possible human carcinogen, and Cancer Research UK has warned about a concentrated aloe product called T-UP marketed as a cure.
Gardeners value aloes as ornamentals, and breeders have even crossed them with related genera such as Gasteria. A hybrid called 'Lizard Lips' won the Royal Horticultural Society's Award of Garden Merit. In one tradition, Aloe variegata is planted on graves in the belief that it secures eternal life.
Source: Aloe
