Scratching a bug bite or rash may seem irresistible, but researchers have found that it usually offers only temporary relief and may prolong the itch. This natural response to skin irritants can increase inflammation and potentially worsen conditions like eczema.
Researchers from the University of Pittsburgh have noted that, although scratching exacerbates swelling, its overall impact and evolutionary benefits are not well-understood. A team led by Professor of Dermatology and Immunology, Daniel H. Kaplan, applied an allergen to the ears of mice to investigate allergic-contact dermatitis, akin to eczema.
The study involved mice exhibiting skin reactions similar to those prompted by poison ivy, certain metals like nickel, and some skincare products. The mice were divided into groups, one labeled as ‘normal’ and the other genetically altered to lack itch-sensing neurons.
The findings suggest scratching may activate mast cells, part of the body’s defense system, releasing histamine and causing further itchiness.
Mice permitted to scratch released substance P, triggering increased mast cell activity and greater inflammation, prolonging the itch-scratch cycle. In contrast, mice prevented from scratching with collars and those lacking itch-sensing neurons showed reduced inflammation.
Scratching offers a satisfying response, which has evolved over millions of years according to Science. Mast cells, while providing protection against pathogens, may also affect skin bacteria.
Further experiments indicated that scratching reduced levels of Staphylococcus aureus, a bacteria often linked to skin infections. However, Professor Kaplan noted the damage caused by chronic scratching likely surpasses its benefits, despite scratching feeling pleasurable.
To have evolved, this behavior must offer some advantage, possibly defense against bacterial skin infections. Cold compresses and 1% hydrocortisone cream could alleviate itching, according to the American Academy of Dermatology. The research findings were published last year in the journal Science.