Buzz
It seems counterintuitive: scratching an itch, which gives immediate relief, actually makes the sensation worse. Evolutionary biologists suggest that this relationship formed when parasites and insects that carry diseases bit humans, causing itching skin. Scratching helped remove the pests. Anyone who’s ever had a mosquito bite can relate to this connection.
The reason skin becomes even itchier after scratching isn't straightforward, but researchers have pinpointed several mechanisms contributing to this aggravating experience.
Why Scratching an Itch Doesn't Provide Lasting Relief
Our sensory neurons are constantly flooded with various stimuli, so some sensations take priority over others. If a particular type of sensory signal is strong enough, it can block others from reaching the brain by being intercepted by specific neurons in the spinal cord. This is why the pain from scratching can often override the itch, but only for a short time.
In the brainstem, cells release serotonin, a neurotransmitter that helps alleviate pain. However, Zhou-Feng Chen, Ph.D., director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis, Missouri, discovered that serotonin has an additional role. His team has found that as serotonin spreads through the spinal cord, it can activate neurons that transmit itch signals to the brain, driving us to scratch even more.
Every time we scratch, we trigger this cycle. The increasing serotonin levels may prompt us to scratch even harder, to the point where the urge to scratch is no longer linked to a physical itch on the skin. 'It’s an attempt to suppress the itchy sensation, which originates in your brain,' Chen explains to Mytour. Through this process, itching can become a chronic issue.
Scratching worsens an itch not only through serotonin signaling but also by causing damage to the skin. 'When the skin barrier is irritated or further harmed, it releases pro-inflammatory factors that directly worsen the itch by stimulating sensory nerve fibers,' explains Brian Kim, M.D., co-director of the Center for the Study of Itch. These factors can also activate the immune system, with certain immune cells around the affected area producing chemicals that trigger more itching.
The very thought of scratching can be enough to set off an itch. Chen’s research group reported last year that mice seem to be influenced to scratch after watching other mice do the same. 'Itching is actually contagious—between people, animals, and even within your own body,' says Chen. 'When you scratch one spot, it’s hard not to want to scratch somewhere else.' Scratching not only intensifies the itch but can also spread the sensation.
Finding Relief for Itching
In mild cases, resisting the urge to scratch might be possible with sheer willpower—but this is rarely a sustainable solution.
"I always feel bad because a lot of people tell patients, 'Don't scratch, don't scratch,' but that's really hard to do," says Kim to Mytour. He emphasizes the importance of first determining the cause of the itch. If it's related to an underlying health condition, like lice infestation or liver disease, treating that issue might alleviate the itch. Even when the root cause can't be fixed, medications such as antihistamines for allergy-driven itching or topical corticosteroids for skin-related conditions, including eczema, can help calm the sensation.
For now, medications like these are our best defense against itching. "I think itch is often seen as a quirky, insignificant, or embarrassing issue," says Kim, which could explain why research on itching remains scarce despite its significant impact on people's lives. Sadly, the elusive 'scratch in a bottle' is still not a reality.
