New research published in the journal Science uncovers how scratching aggravates inflammation and swelling in a mouse model of a type of eczema called allergic contact dermatitis.

“At first, these findings seemed to introduce a paradox: If scratching an itch is bad for us, why does it feel so good?” said senior author Daniel Kaplan, M.D., Ph.D., professor of dermatology and immunology at the University of Pittsburgh.

“Scratching is often pleasurable, which suggests that, in order to have evolved, this behavior must provide some kind of benefit. Our study helps resolve this paradox by providing evidence that scratching also provides defense against bacterial skin infections.”