Why Getting Old Gives You Itchy Skin
Science & Tech / /
Aside from wrinkles, losing the muscle tone, memory and hair loss, many elderly people have supersensitive skin that gets itchy even at the lightest touch—a condition, called alloknesis. There isn’t a known causes or a way to treat this condition yet.
A study in mice has revealed a mechanism for this disorder: a loss of pressure-sensing cells in the skin. Although the findings were based on mice, the researchers believe that boosting the function of these cells could treat chronic itch in people, both young and old.
It should be distinguished, chronic or mechanical itch is different from chemical itch, which is a result of immune system’s reaction to a foreign substance. On the other side, chronic or mechanical itch is caused by light pressure, such as the brush of fibers from a sweater.
“The condition is maddening, and when people repeatedly scratch their fragile, dry skin, it can lead to major health problems, including infections”, says study author Hongzhen Hu, an anesthesiology researcher at the Washington University School of Medicine in St. Louis, Missouri.
Hu and his team of experts used a hair-thin nylon filament for applying pressure on a shaved skin of young and old rodents’ necks. Conclusion: young mice didn’t respond much to the gentle touch, but the older mice scratched furiously. When analyzing skin samples from both mice, the team realized that older mice had far fewer pressure-sensing Merkel cells compared to young mice.
The fewer Merkel cells a mouse had, the more their touch-related itch problems increased in response to the filament, the researchers reported.
The team than tested how young mice with lack of Merkel cells would respond to the nylon fiber. There was again intense scratching, confirming that the Merkel cells were essential for putting itchying sensations under control. As Science Mag reports, they also boosted the activity of Merkel cells that had been genetically engineered to fire when exposed to a chemical called clozapine N-oxide, and found that it reduced scratching in mice with an itchy skin condition. The finding suggests that increasing Merkel cell activity could help treat alloknesis in people.
Other studies have already shown that Merkel cells in people with dry skin and elderly people are reduced. Hu and his team are now analyzing skin biopsies from patients with mechanical itch problems to see whether their Merkel cells are also depleted.
Although the evidence suggests that Merkel help in reducing the mechanical itch, the mechanism for producing the signals is still not known.