Cowhage

The researchers rubbed roughly the same number of cowhage spicules the itch-inducing spiky bits of that plant, also known as velvet bean on three locations: the front of the ankle; on the underside of the forearm; and under the shoulder blade on the back. ❋ Jeremy Singer-Vine (2012)

Many other plants are also known to produce cutaneous irritation in certain subjects; among these may be mentioned the nettle, primrose, cowhage, smartweed, balm of Gilead, oleander, and rue. ❋ Henry Weightman Stelwagon (1886)

Page 132 or unburnt bricks, paving and roofing tiles, gas retorts, and roofing slates; coal, coke, and culm of coal; cochineal; cocoa nuts, cocoa and cocoa shells; coculus indicus; coir yarn; codilla, or tow of hemp or flax; cowhage down; cream of tartar; cudbear. ❋ Confederate States Of America (1864)

British Journal of Dermatology, healthy male and female volunteers aged 22 to 59 were made to itch by rubbing them with cowhage, a plant with tiny hairs that irritate the skin. ❋ Roger Dobson (2012)

Just in case you're not familiar with cowhage spicules, they are tiny threads taken from a tropical legume. ❋ Unknown (2012)

Just take it on faith that when applied to a human's skin, cowhage spicules reliably induce intense itching. ❋ Unknown (2012)

The quantity of saliva may also be increased beyond what is natural, by the catenation of the motions of these glands with other motions, or sensations, as by an extraneous body in the ear; of which I have known an instance; or by the application of stizolobium, siliqua hirsuta, cowhage, to the seat of the parotis, as some writers have affirmed. ❋ Erasmus Darwin (1766)