The rash, which has spread from the crook of my elbow to the base of my wrist, is starting to sprout puffy, crimson welts. It's been three minutes since I rubbed a mound of coarse blond fibers onto my forearm, and what began as a mild prickling sensation has escalated into a throbbing itch. Diana Bautista doesn't seem concerned. "Will scratching make it worse?" I ask. She nods. "Yes, but it will feel really good while you're doing it."

This unsanctioned self-experiment is taking place in the kitchenette of Bautista's University of California, Berkeley, lab. The source of my discomfort is itch powder, the kind anyone can pick up at a novelty store. Its blue packet shows a cartoon man writhing in agony. Below him, in bold letters, are the words, SURPRISE THAT SPECIAL FRIEND! "It's kind of weird people can just buy this stuff on Amazon and not know what it is," Bautista says. A professor of cell and developmental biology, she's pretty sure she knows what the ingredients are: rose-hip hairs and fiberglass. Itchy stuff for sure, but there are far more distressing things in her lab.

Bautista is one of a small but growing number of researchers in the United States trying to decode the molecular secrets of itchiness. She arrived at the specialty the way many others in her field have: by studying pain. For most of medical history, itch and pain were considered variants of the same sensation — itch being just a mild form of pain. What Bautista and others have shown is that while the two share many cellular receptors and molecules, itch has its own biological infrastructure. It's these largely unmapped internal pathways that Bautista has been working to identify for the past seven years.

Of particular interest is chronic itch, the opposite of what I'm currently experiencing. Like pain, itch can be acute or chronic. The fibers and hairs I've rubbed onto my forearm produced an acute mechanical itch by stimulating neurons in my skin. This was followed by a strong scratch reflex, which, once succumbed to, temporarily blocked the itch signal from traveling to my brain and released dopamine (the reason scratching feels so good). The problem is this itch-scratch cycle can spiral out of control for people suffering from psoriasis, eczema, liver and kidney disease, or diabetes, causing perpetual misery. Ten percent of the world's population will suffer from chronic itch at one point, making it a molecular puzzle with a potential billion-dollar solution.

"This is where it all begins," Bautista says as we enter a beige room stuffed with lab equipment. To my left is a microscope trained on a petri dish full of human skin cells that come from biopsies. Bautista and her grad students also grow and store skin cells in the room's temperature-controlled incubators, where they wait to be poked, prodded, stretched, and subjected to mustard oil and capsaicin and other compounds.

Bautista says she's most at home in the lab, but every year she and a group of scientists head to the swamps of rural northern Pennsylvania to capture star-nosed moles. The animal's touch organ — a 22-pronged, starfishlike appendage at the end of its snout — is the most sensitive body part in the animal kingdom, packed with ten times as many nerve endings as a human hand. "We've been studying the organ to try and figure out how one might go about building something like it," Bautista tells me. By understanding how the organ functions, scientists hope to gain insight into tactile disorders. The problem? You can't breed star-nosed moles in the lab. Oh, and they die if you don't feed them every four hours. Needless to say, there aren't any moles in Bautista's lab.

"You haven't seen the spiders!" she says. The lab's terrarium is divided into three sections, each with a baby Greenbottle blue tarantula named after one of Donald Trump's wives. Marla and Melania are nowhere to be seen, but Ivana is front and center, staring at us from atop her webbed burrow. "True to form, Ivana is the showy one," Bautista says. Unlike Old World tarantulas that bite to defend themselves, New World tarantulas like these are equipped with superitchy hairs that they pluck from their abdomens and fling at their enemies' faces. When viewed under a microscope, these hairs resemble elaborate feathers. The Trump wives, who are still young, will molt once a month until they reach adulthood, leaving behind their ornate body hair for Bautista to analyze.

In her corner office, Bautista keeps a stuffed-toy version of a star-nosed mole and a pressure-sensitive metal trap she uses to catch the animal. Tubes of wasabi, tarantulas encased in resin, and filament pens for tickling mice feet are scattered across her desk. Bautista scrolls through a PowerPoint presentation from one of her lectures. A video of a lounging cat scratching its rump with one paw pops up on her desktop screen, followed by various photos of insects perched on people's arms and legs. Suddenly, I notice a tingle on the back of my neck, accompanied by a strong urge to scratch.

It's an example of one of the most confounding aspects of the itch sensation: You can get itchy simply by thinking or talking (or reading) about itchiness. Bautista's seen it happen countless times at conferences and during lectures. It raises an obvious question: Does working in an itch lab all day make you an itchy person? Bautista thinks about it for a moment. "I don't think so," she says, "but maybe I've become habituated to it." What about the collection of back-­scratchers on her desk? "Oh, those were just gifts," she says.