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Warning: Reading this may make you itch

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Mosquito bites cause a form of itch that can be dulled with antihistamine drugs. (Courtesy of Flickr.com)

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A chronic itch can lead to depression and an early death. (Courtesy of Flickr.com)

Melanie Coleman, a single parent, is too tired to spend as much time with her daughter as she would like. At night, she is wracked by a constant, chronic all-over itch, which doctors haven't been able to treat. Her only relief: scratching, sometimes so much that her skin breaks and bruises.

"The doctors are throwing everything in the world at me in the hope that it will work," said Coleman, 34, a London resident.

For many of us, itching is a temporary irritation, triggered by histamine, a protein that is released by the body in response to an allergic reaction. These kinds of itches--mosquito bites, poison ivy--can generally be relieved by antihistamine drugs.

Others like Coleman have chronic, "clinical" itches, and doctors don't yet have sure-fire therapies for those non-allergic varieties. But recent studies aimed at understanding the physiology of itching and scratching may change that.

Chronic itch “isn't good for your health," said Dr. Gil Yosipovitch, a dermatologist at Wake Forest University Baptist Medical Center in Winston-Salem, N.C., who is known as the “Godfather of Itch.” Some patients with kidney failure who undergo kidney dialysis suffer a chronic itch, and Yosipovitch said that for this group there is a 17 percent higher rate of mortality, likely because of a constant loss of sleep and fatigue.

Coleman suffers from a liver disease called Primary Biliary Cirrhosis, the main and earliest symptom of which is pruritus, commonly known as itching.

Chronic itching, whatever the cause, can also lead to depression. "I feel helpless to overcome what I'm going through," said Jeni Spamer, 27, of Seattle, one of some 30 million Americans afflicted with eczema, a lifelong skin condition that results in an itchy rash and raw, flaky skin.

"My boyfriend feels the same way, when he sees me scratching like crazy," said Spamer, a database manager for Microsoft. "He can't do anything to help me."

But help may be on the way. Scientists have recently found a clue as to why scratching feels so good. A study by Dr. Yosipovitch, published in January in the Journal of Investigative Dermatology, showed that areas of the brain associated with unpleasant emotions became significantly less active during scratching.

To conduct the study, researchers scratched the lower legs of 13 healthy volunteers with a small brush and monitored their brain signals using magnetic resonance imaging. The study "suggests that scratching may suppress the emotional components of itch and bring about its relief," said Yosipovitch.

The study also showed that some areas of the brain became more active during scratching, including an area in the secondary somatosensory cortex associated with pain sensation and an area in the prefrontal cortex associated with compulsive behavior. “This could explain why we often have a compulsion to continue scratching,” said Yosipovitch.

The goal of Yosipovitch's research is to find drugs for chronic itch that replicate the relief that scratching provides, so that the patient doesn’t resort to tearing at his or her skin.

Scientists are also exploring the relationship between itching and pain, which seem to operate on separate but parallel nerve pathways. The aim is "to find therapies that would stop itch without stopping pain," said Dr. Robert LaMotte, a professor of anesthesiology and neurobiology at Yale University in New Haven, Conn. LaMotte explains that while pain is necessary--to alert us that our body is being harmed--itch has no obvious evolutionary value.

In the case of liver diseases such as the one afflicting Coleman, for example, LaMotte asks, "What good does it do to scratch nothing?"

Pain takes one route to the brain, but scientists recently discovered that itch takes a second pathway, said Matthias Ringkamp, assistant professor of neurosurgery at Johns Hopkins University in Baltimore. Ringkamp is trying to determine what sort of nerve fibers relay the itch message to the brain. When the pathway is eventually mapped, drugs can presumably be developed to inhibit the itch signals traveling along it.

Significant progress is already being made toward new therapies based on the notion of a second pathway, said Ringkamp. Pharmaceutical companies are pouring money into the effort to develop drugs that can dull a non-histamine itch, he said.

These efforts are crucial, because current treatments for the underlying diseases that trigger itch often don’t quell the itch and can be dangerous when overused, said Ringkamp.

Spamer, for instance, has used steroid creams at times to reduce inflammation when it flares up, but steroids can be harmful if used over a long period of time, causing a permanent thinning of the skin. And other eczema sufferers don’t respond to steroids at all.

In another direction, Dr. Yosipovitch is investigating what one might term the “psychology of itch.” Why do we seem to feel itchy just when we just think about it, or when we watch another person scratch?

Others in the “itch” science community dismiss the study of psychological triggers as “pop science.” LaMotte, for his part, believes that there may be a “hierarchy of itch:” We are always itching all the time, but we only notice the itch when we concentrate upon it--or when a stronger itch is scratched away. “You scratch an itch, another one appears,” he notes.

Even reading this sentence may momentarily bring a prickly tingle to some people, but for many others itchiness is a constant plague.

Coleman, desperate for help, has tried all the available treatments, including prescribed drugs, liver dialysis and special skin-soothing clothing, but nothing has worked.

“They just don’t know what to do with me,” she said. A liver transplant is next on the list.

E-mail: ljw2121@columbia.edu