The pain work led to an interest in itch, and Bautista has accumulated a variety of agents that stimulate the itch reflex, including the plant called cowhage (Mucuna pruriens) and the drug chloroquine, an antimalarial that often causes a hellish, all-over itch.
Both chloroquine and cowhage, however, cause a histamine-independent itch, as do opium compounds; inflammation, from asthma and allergies to skin rash; and eczema.
To study the itches in the lab, scientists turned to cowhage, a major ingredient in pranksters' itching powder.
You can take Benadryl all day, and if you jump into a cowhage plant, you'll itch like no tomorrow," says Giesler, whose University of Minnesota research group was, in 2004, one of the first since the 1950s to take advantage of cowhage's itchiness.
To draw distinctions between itches, a team of researchers led by Ringkamp conducted experiments using histamine for the usual itch and using cowhage to represent chronic itch.
Researchers at the Wake Forest School of Medicine in north Carolina made healthy volunteers aged between 22 and 59 itch by rubbing their ankles, backs and forearms with cowhage
, a plant with tiny hairs that irritate the skin.