An Itch That Can't Be Scratched (And What to Do About It)

Itchy skin, itchy eyes, and itchy rashes can drive anyone to distraction, and chronic itch is a common problem.

What kinds of conditions cause chronic itching? An itch that just won't quit is a common complication of eczema. Chronic itch is a frequent result of allergies, kidney disease, and diabetic neuropathy. People who use opioid drugs like Vicodin or Oxycontin, whether by prescription or illicitly, often have to deal with itchy skin. All of these conditions are becoming more and more common, especially opioid abuse. About one in five people has to deal with a condition causing chronic itching at some point in life, and common medications don't do a very good job of providing itch relief.

What's Wrong With Anti-Itch Medications?

There are some causes of itching that medicine can control fairly well. Allergic itching is relatively easy to stop because it is the result of misdirected activity of the immune system. Turn off the production of histamine with an antihistamine, and the itching stops. Medication for allergic itch usually works.

Other kinds of itching aren't as easily controlled by medication. Part of the treatment for eczema involves restoring moisture to the skin, but choosing the wrong moisturizer can make itching worse. Itching caused by neuropathy can only be treated by restoring nerve function (until recently, old-style antidepressants called MAOI inhibitors might have been used for this purpose), and itching that results from opioid use and abuse is only responsive to discontinuation of the opioid medication. For most of us, the best remedy for an itch is to scratch.

Why Does Scratching Relieve Itching?

It seems a little odd that we humans are put together in ways that make the infliction of pain and tissue injury, by scratching ourselves with our fingernails, as the way to stop the sensation of an itch. The reason scratching itches works has to do with the way our nervous system transmits sensations from the skin.

The sensory nervous system doesn't consist just of long neurons connecting the skin to the spinal cord. There are also smaller structures called interneurons. Sometimes interneurons amplify a nerve signal. Sometimes they stop it from being transmitted at all. The painful sensation of scratching stops the sensation of an itch because the interneurons block scratching signals. To the brain, it is more important to be informed if there is skin injury than it is to be informed of an itch.

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The problem with scratching is that it injures the skin, and the process of healing the skin creates even more itching. However, painful scratching isn't the only way to stop the sensation of itching.

• Pressure sensations also override the sensation of itch. Placing steady pressure on itchy skin will stop the itching.
• Cold or cool sensations make contact with a kind of interneuron that can also override the sensation of an itch. A cold compress may be exactly what is needed to stop itching skin.
• Certain chemicals also activate interneurons that stop itching sensations. Menthol, for instance, soothes an itch, as does neem. Capsaicin (the chemical in hot peppers) also stops itching, but with the sensation of burning.

What Else Can Be Done About Chronic Itching, Such as Opioid Itch?

Biologists believe that itch developed as a tool to keep parasites from spreading from one person to another. When our ancestors had an itch, they would scratch, removing the parasite from their skin. Even in the twenty-first century, various kinds of parasites can provoke itches. Some itches that aren't politely scratched in social settings, such as a perianal itch or itches of the reproductive organs, often are triggered by parasitic infections. Treat the infection, and you get rid of the itch.

However, if you don't or can't treat the infection that is causing the itch, there can be another problem. All of us are prone to contagious itch. If we see someone else scratch, as a holdover from the era when skin parasites were common, we want to scratch, too. The worse your itch, the more you will want to imitate others when you see them scratch. It's important to avoid other people who can't control their scratching (and politely to do your own scratching in public) if you have a chronic itching condition.

No matter what kind of condition is causing chronic itching, however, you need to keep in mind that the more you scratch, the more you will want to scratch. The act of scratching is often painful, but it activates pleasure centers in your brain. Even the pain of broken skin can feel good when you have a chronic itch. 

Conversely, even the absence of pain can feel bad when you have a chronic itch. That's the problem with opioid itching. Taking morphine or codeine or oxycodone or hydrocodone or heroin stops pain. It deactivates the interneurons that convey pain signals to your brain. Without these interneurons to interdict the sensation of itching, however, you may just replace chronic pain with a chronic itch. The more of the opioid you take to control the itching, the more you itch, and the more of the drug you want. Opioid itching can become a vicious cycle that can't be stopped without a doctor's help.

So what can anyone who has a chronic itch do for relief?

• Don't scratch. The more you scratch, the more you stimulate a part of your brain known as the precuneus, and the more it will activate pleasure circuits that tell you scratching feels good, that is, scratching feels good until you stop. Then your itch will bother you even more.
• Instead of scratching, apply pressure or mild cold. Pressure and cooling sensations override the sensation of itch. However, be careful how you cool your skin. Rubbing alcohol can kill skin cells so that you feel an even worse itch after the cool sensation wears off.

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• Stay away from "itchy" people. You'll want to scratch when they do, and this makes you want to scratch more and more. Also, if they happen to carry a skin parasite that makes them itch, you don't want to catch it.
• Learn to recognize that not all itches are equal. Different itches generate different sensations. You can learn to distinguish an itch that you can ignore from one you can't, and avoid the triggers and stresses that set off the more troubling itches.
• See a doctor about medication if your itching is caused by diabetic neuropathy. There are medications now that usually help. It also helps to keep your blood sugar levels under good control.