It Feels Good, and Everybody Does It

Were you surprised by the brain's reaction?
Absolutely. What we found was that activity in certain brain areas, such as the anterior cingulate cortex and posterior cingulate cortex, was reduced. The cingulate cortex areas are linked to a lot of different things. The anterior region is activated when people think of difficult experiences or when you remember an unpleasant sensation like burning your hand. The posterior area is associated with memory.

So for these two areas to show decreased activity with the scratch lends credence to the conventional wisdom that scratching is actually pleasurable. It seems that the reflex of scratching suppresses the emotional components of the itch, the misery of it, and brings about its relief.

Were there brain areas that were made more active?
Yes. The secondary somatsensory cortex, which is associated with tactile stimulations, like touch and pain. And the prefrontal cortex, which is associated with executive functions, like defining goals, as well as obsessive behaviors.

Now that we have a somewhat better understanding of the processes, we might be able to devise some better treatments that work directly on the brain (for those whose scratching has become debilitating).

Until we get there, can we all just continue to scratch away?
Animals scratch, and humans scratch. It helps remove irritants. It's an evolutionary defense mechanism, a reflex. But scratching an itch, though pleasurable, can really damage the skin if you go overboard.

Is there an itch we can't scratch?
Actually, yes: hives. Though there is a lot of histamine and swelling, you don't see patients scratching much. Although you would think they would be scratching like crazy. We don't know why they don't find relief from scratching.