Study links scratching to heightened eczema inflammation and altered skin bacteria
Researchers at the University of Pittsburgh found that scratching intensifies inflammation in eczema-like skin conditions by activating mast cells, while also reducing certain bacteria, suggesting a complex trade-off.
University of Pittsburgh scientists discovered that scratching an irritated skin area can worsen inflammation in eczema-like conditions. In experiments, mice with allergic-contact dermatitis that were allowed to scratch showed increased activation of mast cells and higher levels of the signaling molecule substance P, leading to a prolonged itch-scratch cycle. By contrast, mice prevented from scratching or lacking itch-sensing neurons exhibited reduced inflammation.
The researchers noted that mast cell activation releases histamine and other inflammatory chemicals, which amplify itching. Although scratching lowered the presence of Staphylococcus aureus, a bacterium linked to skin infections, the team warned that the skin damage caused by chronic scratching likely outweighs this benefit. "The damage that scratching does to the skin probably outweighs this benefit when itching is chronic," said study lead Daniel H. Kaplan.
Kaplan added that the pleasurable sensation of scratching may have evolutionary roots, but the new findings suggest its defensive role against bacterial infection is limited. The American Academy of Dermatology recommends cold compresses and low-strength hydrocortisone cream to alleviate itching. The study was published in Science last year.