Scratching an itchy bite may bring instant satisfaction, but new research shows it comes at a cost. Scientists at the University of Pittsburgh discovered that scratching can worsen inflammation and prolong the irritation rather than relieve it.

Led by Daniel H. Kaplan, a professor of dermatology and immunology, the research explored what happens when the body reacts to an allergen that causes itchiness. The team studied mice to understand how the urge to scratch affects inflammation over time.

To begin, researchers exposed the mice to allergens that triggered allergic contact dermatitis, a reaction similar to what people experience after exposure to poison ivy or certain metals. Some mice were allowed to scratch freely, while others wore Elizabethan-style collars that prevented scratching.

Another group of mice was genetically modified to lack an itch-sensing neuron. This allowed scientists to compare how the body’s inflammatory response changed when the sensation of itch was reduced or removed.

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The researchers found that scratching led to the activation of mast cells, a type of immune cell described by the Cleveland Clinic as part of the body’s “alarm system.” These cells release histamine and other chemicals responsible for both itching and inflammation.

The team observed that the mice allowed to scratch produced more of a signaling molecule called substance P, which further activated mast cells. This process set off a cycle of worsening irritation and swelling, making the itch last longer.

Meanwhile, the mice that were prevented from scratching — as well as those missing the itch-sensing neuron — exhibited less inflammation and fewer signs of prolonged irritation. The findings suggest that scratching does not calm inflammation but instead fuels it.

As summer brings a surge in mosquito bites, the researchers cautioned against giving in to the temptation to scratch. The short-term relief, they found, only deepens the skin’s inflammatory response.

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Despite this, the study acknowledged that scratching likely evolved for a reason. According to Science, the ability to feel itch and respond to it is hundreds of millions of years old, indicating an ancient biological advantage.

The researchers wanted to know whether scratching might still provide some benefit. Because mast cells play a role in defending against bacteria, the team investigated how scratching might influence the skin’s microbiome.

In a follow-up experiment, they discovered that scratching reduced the presence of Staphylococcus aureus, a bacterium often involved in skin infections. Kaplan noted that this finding offered a partial explanation for why scratching feels instinctively rewarding.

However, he cautioned that the harm from scratching, especially when chronic, far outweighs its limited bacterial defense. “The damage that scratching does to the skin probably outweighs this benefit when itching is chronic,” Kaplan said.

He also reflected on the paradox of scratching. “At first, these findings seemed to introduce a paradox: If scratching an itch is bad for us, why does it feel so good?” he said. Kaplan added that the evolutionary pleasure of scratching likely developed because it once offered protection against infection.

The American Academy of Dermatology recommends non-damaging ways to find relief, including cold compresses and 1% hydrocortisone cream. The University of Pittsburgh team published its findings in the journal Science last year.

Their work ultimately suggests that resisting the itch may be the healthier choice. While scratching might feel good in the moment, the science shows it only keeps the irritation — and inflammation — alive longer.