Scratch that itch! It feels good, certainly for awhile. Usually, then, the skin reddens and the itch returns, maybe for several days. It’s a natural reaction, built into our sensory system; is it productive, useful, or is it just a sideshow, or even negative?
The scratch reaction evolved, but not everything that evolves is beneficial or even balanced in good and bad effects. So, Andrew Liu and 20 colleagues at the University of Pittsburgh looked at the nerve cells that create the itch and then details of how several types of cells respond to scratching. They chose to study the itch and scratch in mice for obvious reasons. In any case, this behavior is strongly conserved in animals – mice do it, you do it, dogs do it, and on and on.
The researchers cross-bred two lines of mice and then knocked out a type of neuron. They used proteins that fluoresce green to see the activity of genes in other neurons. It’s a bit complicated, but the results show that scratching triggers special skin cells called mast cells to generate an inflammatory reaction. No surprise there, but the cells also generate an immune response against common skin bacteria. That may reduce the chance of an infection, or increase it.
Scratch carefully.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org
Source: Science, 31 Jan., pp. 489 ff.
Image : Same
