The Origins of an Itch
How would you describe the feeling that prompts you to cough? A tickle in your throat? A scratchy throat? From an anatomical perspective, you’d be more accurate calling it an itch, according to a study recently published by Xinzhong Dong, a Johns Hopkins neuroscientist.
Dong and his team discovered that our throats contain itch receptors identical to the ones in our skin. When pollen, dust, or mucus triggers those receptors, our throats feel irritated or itchy.
Dong is an expert in, well, itchiness. In 2012, he was the first to identify the receptors in skin that lead us to feel an itch. He also discovered that a small amount of pain can block the sensation—and the same mechanism is at work in the throat. “Unlike in the skin, we can’t scratch an itch in our throats,” he says. “Instead we cough, which causes a slight pain that blocks the itch.”
“Unlike in the skin, we can’t scratch an itch in our throats. Instead we cough, which causes a slight pain that blocks the itch.”
After hearing asthma sufferers complain of an itchy sensation in the lungs before an attack, Dong began his hunt for itch receptors in the airways. He and his team discovered them on nerve cells in the throats of mice. They found that when these receptors are stimulated, the surrounding cells constrict, much as throat cells do in a human who is coughing. But in mice bred without itch receptors, the cells do not constrict when the nerve cells are stimulated.
This could have big implications for the 25 million Americans who suffer from asthma, one of the most common and costliest chronic diseases. The Centers for Disease Control and Prevention estimates it costs more than $81 million annually to treat asthma. And while inhalers can help many sufferers control symptoms of breathlessness and wheezing, the disease can have serious side effects: Asthma leads to 1.8 million trips to the emergency room each year and 13.8 million missed days of school, according to CDC reports.
While an itchy throat can send a useful message to most people—a warning to avoid smoke or dust— it can trigger an attack in those with asthma.
And while an itchy throat can send a useful message to most people—a warning to avoid smoke or dust—it can trigger an attack in those with asthma. Dong and his team hope their discovery can spur new treatments for asthma and chronic coughing, and they are working with a pharmaceutical company to devise such a drug. “If you could develop a blocker of an itch receptor, you could potentially stop asthma symptoms,” Dong says.