Euphorbia poissonii, also known as Euphorbia poissoni  and, incorrectly as Euphorbia poisoni is a highly irritant and toxic succulent member of the large and varied spurge family of plants. It is native to northern Nigeria, where local farmers extract its latex for use as a pesticide. Its powerfully irritant and pain-producing nature mandates use as a fencing plant.
In addition to a variety of irritant phorbol-type esters, the latex contains resiniferatoxin and tinyatoxin, two closely related highly irritant resiniferonol-type esters. The most active toxin, resiniferatoxin, binds to pain receptors in the same way as capsaicin but much more powerfully. It stimulates the neurons to fire repeatedly, causing pain.
Nicolaou, K. C. and Snyder, Scott A. Classics in Total Synthesis Vol. II. Wiley VCH, 2003. Chapter 6.