The hottest hot pepper is no match for the spicy heat of the resin spurge Euphorbia resinifera, a cactus-like plant native to Morocco. The resin spurge produces a chemical called resiniferatoxin, or RTX, which is a thousand times hotter on the Scoville scale than pure capsaicin, the chemical that produces heat in hot peppers. Law enforcement-grade pepper spray and the hottest hot pepper, the Trinidad Moruga Scorpion, both pack a punch of about 1.6 million Scoville heat units. Pure capsaicin comes in at 16 million Scoville units, while pure resiniferatoxin has 16 billion—yes, billion—Scoville heat units.

Both the capsaicin from hot peppers and the resiniferatoxin from the Euphorbia can give you chemical burns or even kill you. Resiniferatoxin makes the plasma membrane of sensory neurons permeable to cations, especially calcium. Initial exposure to resiniferatoxin acts as a strong irritant, followed by analgesia. Even though the chemicals may be painfully hot, both capsaicin and resiniferatoxin can be used for pain relief.