Cause of Itchy Skin Discovered
Who hasn’t had itchy skin that drives them crazy? People who suffer with psoriasis, eczema, allergies, and other irritating skin conditions have often known the agony of scratching themselves until their skin is raw, or worse. Now researchers say they have found specific nerve cells that cause itchiness, a find that could eventually lead to effective treatments for a wide variety of itchy skin conditions.
Scientists had long thought that itchiness and pain were closely related, which complicated their efforts to find an effective way to treat both sensations. Now investigators have discovered that there are certain neurons (nerve cells) that can cause itchy skin but not pain.
According to Zhou-Feng Chen, the study’s lead researcher, this finding is significant because “those cells may contain several itch-specific receptors or signaling molecules that can be explored or identified as targets for future treatment or management of chronic itching,” as noted in a August 6, 2009, Science Daily report.
Zhou-Feng Chen has been on the trail of what causes itchiness and itchy skin for some time. In 2007, he and his team of scientists at Washington University School of Medicine in St. Louis identified the first gene for the itch sensation in the central nervous system. It was their hope at that time that their discovery would soon lead to new treatments for chronic and severe itchy skin conditions. This latest study brings them much closer to that goal.
According to the National Psoriasis Foundation, the itchy skin condition is the most prevalent autoimmune disease in the United States. Approximately 7.5 million Americans (2.2% of the population) has the disease, with about 125 million people worldwide suffering with the condition.
The American Academy of Allergy, Asthma and Immunology reports that 10 to 20 percent of children and 1 to 3 percent of adults have atopic dermatitis (a type of eczema). Acute hives will affect up to 24 percent of people in the United States at some point in their lives. Contact dermatitis (an itchy skin condition caused by contact with an irritant or allergen) leads to approximately 5.7 million doctor visits each year, putting a tremendous strain on the health care system. More than 3,700 substances have been identified as contact allergens.
The itchy skin gene, called gastrin-releasing peptide receptor, or GRPR, was first identified in the spinal cord of mice. The researchers first took mice and destroyed the nerve cells that had active GRPR, then exposed the mice to things that cause itching. The mice did not itch but they did feel pain.
The researchers proved that neurons with GRPR are necessary for normal itchiness and by extension, itchy skin conditions. Their findings also indicate that itch and pain signals are transmitted along different pathways in the spinal cord, and that they can stop the itch response in mice without affecting their ability to sense and avoid pain. The scientists emphasize that they “still have a lot of questions” and so it is uncertain how long it will be before effective treatments for psoriasis, eczema, and other itchy skin conditions are available.
American Academy of Allergy, Asthma and Immunology
National Psoriasis Foundation
Science Daily 8/6/09
Sun YG et al. Science August 7, 2009
Sun YG, Chen ZF. Nature online July 25, 2007; (448): 700-703.