Cacti are admired for their resilience and unique appearance. While most true cacti are not chemically toxic to humans or animals, a select few species contain compounds that can cause adverse effects if ingested. Beyond chemical toxicity, all cacti present physical hazards due to their spines and irritating bristles.
Identifying Truly Toxic Cacti
A few cactus species produce chemical toxins, primarily psychoactive alkaloids. Among these, Lophophora williamsii (Peyote) contains mescaline, a hallucinogenic compound. This small, spineless cactus has been historically used in traditional and ritualistic contexts.
Species within the Echinopsis genus, including Echinopsis pachanoi (San Pedro), Echinopsis peruviana (Peruvian Torch), and Echinopsis lageniformis (Bolivian Torch), also contain mescaline and other phenethylamine alkaloids. These columnar cacti are known for their psychedelic effects if consumed.
The Fishhook Barrel cactus (Ferocactus wislizenii) can induce temporary paralysis if ingested. It is important to differentiate true cacti from plants like Euphorbia species that resemble them but belong to other families. Plants like the Pencil Cactus (Euphorbia tirucalli) are often mistaken for cacti due to their succulent, spiny appearance, but are not true cacti. These Euphorbia plants produce a milky white sap that is irritating and toxic if ingested or if it contacts skin or eyes.
Symptoms of Exposure
Exposure to toxic cacti can cause a range of symptoms, varying in severity based on species, amount consumed, and individual sensitivity. Ingesting mescaline-containing cacti like Peyote or San Pedro can lead to gastrointestinal upset, including nausea, vomiting, and diarrhea. Beyond digestive issues, these psychoactive compounds can cause confusion, hallucinations, and psychological effects like anxiety, paranoia, or psychosis. While mild cases may resolve on their own, severe reactions can include respiratory distress or cardiac effects.
Contact with toxic sap from plants like the Pencil Cactus can cause immediate skin irritation. This irritation causes redness, itching, and blistering. If sap contacts the eyes, it can result in severe pain and temporary blindness. For pets, ingesting toxic cactus species or sap can lead to symptoms like excessive drooling, vomiting, and lethargy.
Beyond Chemical Toxicity: Other Cactus Hazards and Safety
Beyond chemical compounds, all cacti pose physical hazards. Their sharp spines can cause puncture wounds, leading to pain, swelling, and a risk of infection if not properly cleaned.
Some cacti, particularly Opuntia subfamily members like the Prickly Pear, are covered in tiny, barbed hairs called glochids. These glochids detach easily and embed in the skin, causing intense stinging, burning, itching, and small bumps or rashes. Unlike larger spines, glochids are difficult to see and remove due to their microscopic size and backward-pointing barbs.
To handle cacti safely, research the species and use protective gear like thick gloves and protective eyewear. Keep cacti, especially known toxic varieties or those with easily detachable spines, out of reach of children and pets.
For minor spine or glochid injuries, use duct tape or white glue to lift out the tiny bristles. For larger spines, use sterilized tweezers to pull them out at the same angle they entered. After removal, the affected area should be thoroughly cleaned with soap and water to prevent infection. Seek professional medical attention if signs of infection develop, such as increased redness, pain, swelling, pus discharge, or fever. Medical consultation is advised for deep puncture wounds, retained spine fragments, or severe allergic reactions.