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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.
- Manuel P. Pereira
- Andreas E. Kremer
- Thomas Mettang
- Sonja Ständer. Chronic Pruritus in the Absence of Skin Disease: Pathophysiology, Diagnosis and Treatment. Am J Clin Dermatol. 2016. 17(4):337-348.
- Photo courtesy of mauritsverbiest: www.flickr.com/photos/mauritsverbiest/26853776484/
- Photo courtesy of centralasian: www.flickr.com/photos/centralasian/5565136539/
- Photo courtesy of centralasian: www.flickr.com/photos/centralasian/5565136539/
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