21 Poisonous Aloe Species (Explained With Pictures & Facts)

Poisonous aloe species in a garden in Ohio — Picture: *Aloe*

Poisonous aloe species are far more common than most people expect, because the aloe family is large and only a few of its members are safe to use. Aloe vera is a single species, but it has several hundred relatives across Africa, Arabia and Madagascar. Many of them look alike, and people often call every one of them aloe vera.

The danger comes from two sources. Nearly all aloes hold a bitter yellow sap just beneath the leaf skin, which acts as a harsh laxative and irritant. That sap is the reason aloes are listed as toxic to dogs, cats and horses.

A smaller group is far more dangerous. About a dozen aloes contain the same nerve poison found in poison hemlock, and researchers at Kew found the levels higher than in hemlock itself. Conservationists in Kenya warn that applying or eating the wrong aloe can be fatal.

These hemlock aloes grow far apart, in East Africa, Arabia, southern Africa and Madagascar, and they are not closely related to one another. The 21 aloes below include both groups, and each entry notes where the plant grows.

Alo Vera ina garden in Florida — Picture: Alo Vera

1. Aloe Vera

Aloe vera is the best-known aloe and the one sold for burns and skin care. It forms a stemless clump of thick, gray-green leaves. The leaves have small, pale teeth along the edges. Young plants are spotted with white. It bears yellow flowers on a tall stalk. It is grown as a houseplant around the world.

North Carolina State University lists it as a plant with low-severity poison characteristics. The clear inner gel is the part used on skin. The yellow sap just under the rind is the harmful part. Swallowing it causes cramps, vomiting and diarrhea. It is toxic to dogs, cats and horses. The plant is thought to have originated on the Arabian Peninsula and is grown in warm regions and indoors worldwide.

2. Bitter Aloe

Bitter aloe is a tall, single-stemmed plant. It can reach 6 to 10 feet. Its leaves are thick, dull green and edged with reddish-brown spines. Old, dry leaves hang down around the trunk. It bears candle-like spikes of orange-red flowers. It flowers in winter.

Its yellow sap is the source of a traditional drug called Cape aloes. The dried sap is an extremely strong laxative. Large doses cause severe cramping and fluid loss. Long-term use can harm the kidneys and bowel. It is unsafe in pregnancy. It grows wild across South Africa, from the Western Cape to KwaZulu-Natal, and in Lesotho.

3. Socotrine Aloe

Socotrine aloe is an old medicinal aloe from an island in the Arabian Sea. It forms a short-stemmed rosette. Its leaves are gray-green, often tinged with red. The edges carry small, pale brown teeth. It bears red flowers tipped with green. It grows on dry, rocky ground.

Its dried sap was traded for centuries as a purgative. Ancient Greek writers knew of it. It acts as a violent laxative. Overuse causes pain, bleeding and loss of body salts. It is no longer recommended as a medicine. It grows on the island of Socotra, which belongs to Yemen.

4. Rat Aloe

Rat aloe is one of the most poisonous aloes known. It is a slender tree aloe that can reach 20 feet or more. Its trunk is thin and unbranched. A crown of long, recurved, gray-green leaves sits at the top. Its sap smells strongly of rats or mice. That smell is its best warning sign.

The odor comes from the same nerve poison found in poison hemlock. Kew researchers confirmed the toxin in its leaves in 1984. The poison paralyzes the muscles used for breathing. Conservationists in Kenya name it among three exceedingly poisonous local aloes. It is rare in the wild. It grows in southeastern Kenya and northeastern Tanzania.

5. Ruspoli’s Aloe

Ruspoli’s aloe is a clump-forming aloe of dry East African bush. It has little or no stem. Its leaves are broad, yellow-green and almost toothless. It bears branched stalks of small yellow flowers. Its sap has a strong, ratty smell. It is the most widespread of the three poisonous Kenyan aloes.

Its leaves contain the hemlock toxin. The level found was higher than in poison hemlock. Herders in the region are said to have used it to poison hyenas. Using it on a wound or as a remedy can be deadly. It must never be confused with aloe vera. It grows in Ethiopia, Somalia and northern Kenya.

6. Tall Aloe

Tall aloe is the third of Kenya’s highly poisonous aloes. It grows on a single stem. It can reach 15 to 20 feet. Its leaves are long, spreading and edged with pale teeth. It bears branched heads of yellow to orange flowers. Its sap smells of rats.

It carries the same kind of nerve poison as rat aloe. It is relatively rare and not widespread. That limits the risk to people. The danger arises when wild aloes are harvested for sap. A poisonous species could be collected by mistake. It grows in southern Kenya and northern Tanzania.

7. Yemen Tree Aloe

The Yemen tree aloe is a graceful, tree-like plant. It can reach 10 to 15 feet. Its trunk is slender. Its leaves are long, soft and drooping. They are pale green and nearly smooth-edged. It bears red-brown flowers.

Chemists found three related hemlock poisons in its leaves in 2001. It is the only Arabian aloe in the hemlock group. An older name for the same plant appears in the original Kew study. Its sap should not touch the mouth or broken skin. It is grown by collectors for its elegant shape. It grows in the mountains of southwestern Saudi Arabia and Yemen.

8. Knobbly-Bud Aloe

The knobbly-bud aloe is a stemless plant that forms dense clumps. Its leaves are gray-green and curve upward. They have small white teeth. Its flower stalk branches sideways. The buds are rounded and club-shaped, which gives the plant its name. The flowers are cream to pale pink.

It is known as a dangerous plant in southern Africa. Its leaves contain the hemlock poison. Deaths have followed its use in traditional remedies. Symptoms include weakness, paralysis and failure of breathing. Its bluish foliage and odd buds help identify it. It grows in Zimbabwe, Botswana and the Limpopo region of South Africa.

9. Candelabra Aloe

The candelabra aloe is a large, branching shrub. It can reach 6 to 10 feet tall and wide. Its leaves are narrow, curved and gray-green. Pale teeth line the edges. It bears bright red-orange flower spikes in winter. It is widely planted as a hedge.

The University of Wisconsin notes that aloes form a large group native to Africa and nearby regions. The candelabra aloe has the same bitter yellow sap as aloe vera. The sap causes vomiting and diarrhea if eaten. It is toxic to pets. Its leaf gel is used on burns in some countries. It is native to southeastern Africa, from South Africa to Malawi, and is grown in California, the Mediterranean and Japan.

10. Great Dyke Aloe

The Great Dyke aloe is a rare plant of mineral-rich hills. It is stemless, with a single rosette. Its leaves are blue-gray and edged with reddish teeth. Its flower stalk leans to one side. The red flowers all point upward along it. It grows among grass and rocks.

Its leaves have been found to contain the hemlock poison. It grows only on soils rich in heavy metals. Few plants can live there. Mining threatens its habitat. It should be treated as poisonous. It grows only on the Great Dyke of Zimbabwe.

11. Orange River Aloe

The Orange River aloe is a striking plant of desert cliffs. It is usually stemless. Its leaves are narrow and turn red-brown in drought. They are marked with fine lines. It bears tall spikes of yellow flowers. Red-flowered forms also occur.

It has been reported to contain the hemlock group of poisons. It grows in one of the driest parts of southern Africa. Its leaves store water through long droughts. Animals generally leave it alone. It is grown by succulent collectors. It grows along the lower Orange River, on the border of South Africa and Namibia.

12. Krapohl’s Aloe

Krapohl’s aloe is a small, neat desert plant. Its rosette is only a few inches across. The leaves are gray-green with darker cross-bands. It has tiny white teeth. Its flowers are large for its size. They are red-orange with green tips.

Its leaves contain the hemlock poison. It is one of the smallest aloes in that group. Its beauty makes it popular with collectors. It is hard to grow outside its home climate. Wild plants are threatened by collecting and mining. It grows in Namaqualand, in the northwestern corner of South Africa.

13. Ibity Aloe

The Ibity aloe is named for a mountain in Madagascar. It forms a short-stemmed rosette. Its leaves are green and edged with firm teeth. It bears a tall spike of red to orange flowers. It grows among quartz rocks. It survives regular grass fires.

Kew researchers found the hemlock toxin in its leaves. It is one of three Madagascan aloes with this poison. The amount exceeded that in poison hemlock. Its sap should be kept away from the mouth and from wounds. It is found in few places. It grows in the central highlands of Madagascar.

14. Toothed Madagascar Aloe

The toothed Madagascar aloe is named for the triangular teeth on its leaves. It forms a low rosette. Its leaves are pale green, sometimes with faint lines. It bears dense spikes of white to pale pink flowers. Several forms exist. It grows on rocky outcrops.

It was among the first aloes shown to contain the hemlock toxin. The finding surprised botanists. It is not closely related to the East African poisonous aloes. It is grown in succulent collections. It is safe to handle but must not be eaten. It grows in south-central Madagascar.

15. Viguier’s Aloe

Viguier’s aloe is a cliff-dwelling plant. It has a short stem. Its leaves are soft, pale blue-green and almost toothless. They hang down from rock faces. It bears loose spikes of red flowers. It grows on limestone.

It contains the main poison of hemlock itself. The other Madagascan species hold a closely related compound. A later study confirmed the finding. It is uncommon in cultivation. Its poison makes it unsuitable for any home remedy. It grows in southwestern Madagascar.

16. Descoings’ Aloe

Descoings’ aloe is the smallest aloe in the world. Its rosettes are only an inch or two across. The leaves are dark green and rough with white bumps. It forms tight clusters. It bears tiny red-orange flowers. It is a favorite of collectors.

Despite its size, it contains the hemlock poison. It is widely grown on windowsills. Breeders have used it to create many miniature hybrids. It is harmless to touch. It should be kept from children and pets that chew plants. It grows on limestone cliffs in southwestern Madagascar.

17. Soap Aloe

Soap aloe is a tough garden aloe. It forms a flat rosette up to 2 feet wide. Its leaves are broad and pale green with white spots. Sharp brown teeth line the edges. The leaf tips often dry and curl. It bears flat-topped clusters of orange-red flowers.

North Carolina State University includes it in its plant database. Its sap lathers in water and was used as soap. The sap irritates the skin of some people. Eaten, it causes stomach upset. It spreads by suckers into large colonies. It is native to South Africa and is grown across the southern United States, California and Australia.

18. Mountain Aloe

Mountain aloe is a large, single-stemmed aloe. It can reach 8 to 12 feet. Its leaves are broad and gray-green. They are covered with spines on both surfaces. Its flower stalks spread out sideways. The flowers are orange to red.

It has the bitter yellow sap typical of aloes. The sap is a strong laxative. It has been used in folk medicine and to wean infants. Too much causes cramps and dehydration. The dried leaves were once ground for snuff. It grows in northern South Africa, Eswatini, Botswana, Zimbabwe and Mozambique.

19. Coral Aloe

Coral aloe is one of the few aloes without teeth. Its leaves are broad, flat and smooth-edged. They are pale blue-gray with a pink margin. Fine lines run along them. It bears clusters of coral-red flowers. It is widely used in dry-climate gardens.

Its smooth leaves make it look harmless. It still contains the bitter laxative sap. Pets that chew it may vomit or develop diarrhea. The plant is safe to handle. It should not be used as a substitute for aloe vera. It is native to the Cape region of South Africa and is grown in California, Arizona and the Mediterranean.

20. Tiger Aloe

Tiger aloe is a compact houseplant. Its leaves are arranged in three ranks. They are dark green with bands of white spots. The edges are white and finely toothed. It grows only about a foot tall. It bears pink to red flowers.

Botanists now place it in a separate group from the true aloes. It contains similar bitter compounds. It is considered toxic to cats and dogs. Eating it causes vomiting and diarrhea. It is one of the most common aloes sold for windowsills. It is native to South Africa and Namibia and is grown indoors worldwide.

21. Lace Aloe

Lace aloe is a small, stemless plant. Its leaves are dark green and dotted with white bumps. Each leaf ends in a soft, hair-like tip. It forms tight clusters. It bears orange-red flowers on a slender stalk. It tolerates more cold than most aloes.

It is also now classed apart from the true aloes. It holds the same kind of bitter sap. The sap can upset the stomach of pets and people. It is safe to handle. Its hardiness has made it a popular garden and pot plant. It is native to South Africa and Lesotho and is grown in Europe, North America and Australia.

Key Takeaways:

Not all aloe species are safe to consume: Although Aloe vera is widely used in skincare, some aloe species contain irritating or toxic compounds that make them unsuitable for eating.

Aloe plants contain different chemical compounds: Certain species and plant parts contain anthraquinones and related compounds that can cause digestive irritation or other adverse effects.

The yellow latex can be particularly irritating: The bitter yellow sap found beneath the outer leaf skin of Aloe vera contains aloin and related compounds that can cause abdominal cramps and diarrhea when ingested.

Aloe species vary in appearance: Leaf shape, serrated edges, spotted patterns, growth habits, and flower colors can help distinguish different aloe species, but appearance alone cannot establish whether a plant is toxic.

Some aloe species may cause harm to pets: Ingesting certain aloe plants, including Aloe vera, can cause vomiting, diarrhea, and lethargy in cats and dogs.

Correct identification is essential for safety: Avoid eating or using an unfamiliar aloe plant medicinally. If a person or pet accidentally ingests a potentially toxic aloe, seek advice from a qualified medical professional or veterinarian.