Though it may be tempting to scratch a bug bite or rash, doing so only offers temporary relief and can actually prolong the itching sensation, according to researchers.
Scratching is an instinctive reaction to skin irritants that can heighten inflammation and worsen certain conditions like eczema.
However, the reasons behind scratching enhancing swelling—and whether this evolutionary response offers any advantages—remain “poorly explored,” say researchers from the University of Pittsburgh.
To study the connection between itching, scratching, and inflammation, lead researcher Daniel H. Kaplan, a professor of dermatology and immunology at the University of Pittsburgh, exposed mice to an allergen to induce allergic-contact dermatitis, similar to an eczema flare-up.
The mice exhibited skin reactions comparable to those caused by poison ivy, specific metals like nickel, and certain skincare products.
Scratching an itchy bite or rash is a natural reaction, but it may prolong the cycle, according to research. (iStock)
In the experiment, one group of mice served as a control, while another group was genetically modified to be unable to sense itch.
Some mice could scratch freely, while others were restricted from doing so with an Elizabethan-style collar, often referred to as the “cone of shame” by pet owners.
The researchers discovered that scratching activated mast cells, which the Cleveland Clinic describes as part of the body’s “alarm system” that “detects harmful invaders.”
These mast cells release histamine and other inflammatory substances that amplify the itching sensation.
“Sometimes, they activate unnecessarily, leading to allergic reactions,” noted the Cleveland Clinic.
The study revealed that the mice that scratched freely produced higher levels of substance P, a signaling molecule that activates more mast cells, resulting in greater inflammation and a prolonged itch-scratch cycle.
In contrast, the mice prevented from scratching and those without itch-sensing neurons experienced reduced inflammation.
As bug-bite season approaches, researchers advise against scratching skin irritations, which has been shown to heighten inflammation. (iStock)
While scratching may provide temporary satisfaction, as Science reported, “The ability to sense itch and respond by scratching evolved hundreds of millions of years ago.”
Given that mast cells are “also crucial for protection against bacteria and other pathogens,” the researchers conducted an additional experiment to see if the activation of mast cells from scratching could influence the skin microbiome, as reported by the University of Pittsburgh in a news release.
They discovered that scratching led to a decrease in Staphylococcus aureus, a bacterium strongly linked to skin infections.
However, “the harm caused by scratching to the skin likely outweighs this benefit when itching is chronic,” cautioned Kaplan.
While scratching can diminish some skin bacteria, the drawbacks of inflammation outweigh these benefits, according to researchers. (iStock)
“Initially, these findings appeared to present a paradox: if scratching is detrimental, why does it feel so pleasurable?” Kaplan noted. “Scratching often brings pleasure, which suggests an evolutionary advantage; our study provides evidence that scratching acts in defense against bacterial skin infections.”
The American Academy of Dermatology recommends using cold compresses and 1% hydrocortisone cream to alleviate itching.
The findings were published last year in the journal Science.
- The Associated Press – Fox News Digital.
