What plant's sap can cause severe skin burns when exposed to sunlight?

Giant hogweed is the plant whose sap can cause severe skin burns when exposed to sunlight. Its sap contains furanocoumarins, chemicals that make skin unusually sensitive to ultraviolet light and can trigger phytophotodermatitis.

The reaction may begin within minutes, but redness, blistering, and painful inflammation can develop later. Symptoms can persist for days or weeks, and affected skin may remain sensitive to sunlight for an extended period. Washing the area promptly and avoiding further sunlight are important first steps.

Giant hogweed is native to the Caucasus region and was introduced elsewhere as an ornamental plant. It is often mistaken for less dangerous members of the carrot family, including cow parsley and other hogweeds. Its enormous height and large umbrella-shaped flower clusters help distinguish it, but plants should not be handled without protective clothing.