The relentless itch of psoriasis

The L.A. Times just published an extensive article on itch, and they accurately convey how devastating it can be:

For most people, itching is only a mild annoyance, relieved by a quick scratch or maybe some skin cream. For others, the itch stays, stays -- and stays.

"It starts like any other itch, like you've been bitten or something," said David Hayes, a Los Angeles computer technician who has psoriasis, a noncontagious disease that causes skin inflammation, probably due to an overactive immune system. "But then it keeps on going. You've got to scratch it, and you've got to keep scratching until you're almost bleeding before it stops."

For people like Hayes with psoriasis, or for others with the skin allergy eczema, the sensation can be unbearable. "Itching is the worst thing," says Susan Lipworth of Bloomfield Hills, Mich., who has had eczema for 13 years. "It never stops -- it never stops -- it wears you down." ...

Such itches can erode a person's mental health, experts now say.

Many studies have found that people with severe itching from psoriasis, eczema and kidney dialysis are more likely to be depressed than others. In a 1998 study published in the British Journal of Dermatology, for example, researchers from the University of Western Ontario in Canada reported that almost 10% of 217 patients with psoriasis had had suicidal thoughts.*

For many people, the itchiness also prevents them from sleeping. In a study in 2002, Yosipovitch found that 84% of 102 eczema patients had trouble falling asleep due to itching. ...

Lack of sleep due to itching can affect people's physical health, Yosipovitch says.

[* Of course, it is not just itch that can make someone with psoriasis depressed.] The article then suggests a theory to add to the woes of every itchy person: scratching can make it worse.

But in 1997, Schmelz discovered distinct nerve cells in the skin that respond to itchy stimuli, and itch researchers revised their theories. They now believe that the sensations of itch and pain travel along separate pathways.

In cases of chronic itching, though, things go wrong. Some of the nerves that would normally transmit pain start to send itch signals instead. A 2004 study led by Schmelz, for example, found that people with eczema perceived pinpricks and electric shocks as itchy, not painful.

"The nerves are acting wacky," Yosipovitch says.

In such cases, scratching doesn't make the itch go away -- in fact, over the long run it can make people even more sensitive to itchy sensations. Repeated damage to the skin makes it grow thicker and sprout even more itch nerves.

Yet it's hard to avoid scratching in response to an itch -- even when you know you're doing yourself no favors. "I consider it almost an addiction," said Diana Cordio, a human resources assistant in San Mateo, who has psoriasis. "Scratching the itch -- you know that it's not helping you in any way. But there were some times I would have to break down, and get [finger]nails to skin, or whatever was handy, like a hairbrush."

Of course, as our understanding of a medical phenomenon increases, so does the likelihood of effective treatments:

One now-common treatment for people who itch because of liver disease is to prevent the body's own itch-promoting opioids from working, using drugs such as naloxone or naltrexone (also used to treat morphine overdose and alcoholism). Patients experience less itch -- the downside is they also experience more pain. They often find this preferable. ...

Other opioid-linked drugs are in the works. Last year, Yosipovitch tested one called butorphanol that is known to decrease sensitivity to itch-promoting opioids and increase sensitivity to itch-reducing ones. ...

In yet another opioid-related approach, Japanese researchers at Toray Industries Inc., in Kanagawa, developed a drug called TRK-820 that mimics the action of itch-reducing opioids. They have found that TRK-820 is effective in reducing scratching in mice with eczema. ... In the U.S., Phase III clinical trials are expected to begin later this year. ...

[Dr. Sonja Stander, who runs the Clinic for Neurodermatology in Munster, Germany] has used some pain drugs, including gabapentin (originally used to treat epilepsy), which seems to reduce the excitability of itch nerves. She's also treated patients with capsaicin, the same substance that makes chile peppers spicy.

Initially, capsaicin cream burns when it's smeared on the skin, but in fact it can help in a number of itchy conditions, Stander says, including psoriasis and the itching that often accompanies kidney dialysis. It does so by lowering levels of a chemical called "substance P" that allows sensory nerves in the skin to communicate with the brain. (The nerves detect the itch but can't send the message to the brain.)

Stander's itch clinic has been successfully treating some patients with another drug called aprepitant (Emend) that blocks substance P directly. And sometimes, she says, low doses of antidepressants such as paroxetine (Paxil) or mirtazapine (Remeron) can help.

No one knows quite why, but two pilot studies in the last five years have found that mirtazapine can relieve some people's itching, particularly at night -- even in people who aren't depressed. ...

Treating the itch itself is good, but it would be better to keep the itch-scratch cycle from spiraling out of control in the first place.

People with eczema, for example, sprout extra nerve endings where their skin is inflamed, making them more and more sensitive to itch as the years go by. A substance called nerve growth factor drives the nerves to sprout. It may be one key to stopping the runaway itching.

The article closes with a reminder that reducing the psoriasis on the skin can be the best way to address the incessant, relentless itch that often comes with the disease:

Cordio, whose psoriasis was diagnosed in 1998, has finally managed to clear up most of her skin. She had rough periods in the past: "I've been as much as 90% covered. Let me tell you, that's not a fun way to be."

She's tried a variety of different medications, none of which were particularly effective. Recently, she's started a new drug -- efalizumab (Raptiva), which interferes with the immune cells responsible for skin inflammation. "This was my lucky ticket," she says. "This is the first time in all the years that I've had psoriasis that I've had this significant a clearing."

There's always a worry that her skin will flare up again. "I have a tendency to live in a cautious joy," she says, "but I never know when [the itch] is going to come back."

For now, though, "It's a kind of freedom. There's a freedom from the flare; there's freedom from that constant burden of scratching.

"It is liberating," she says, "when the itch is not there."

If itch is a problem for you, tell your doctor. There are many ways to reduce itch, from Sarna lotion and other moisturizers to antihistamines and other over-the-counter and prescription treatments. And if you scratch, don't beat yourself up over it. Just try to be gentle, and keep looking for ways to reduce the itch in the first place.