Ah, evolution again.

The itch/scratch reaction is an evolutionary development that disposes of parasites before they burrow into your skin, or to get their eggs and larvae off you or out of you, and to remove splinters and stings before they infect you.

Then some nasty diseases like smallpox, chickenpox and plague came along. Their evolutionary adaptation is to make you itch so that you break your skin, release the pustules that carry their spores, and spread them to your family on your hands. That (and the horrible scars that smallpox gives you) is the reason that scratching is socially discouraged now.

Of course, scratching was also an admission you had body lice, so a bit of a social stigma there, too.

Paul's response was largely what I had had in mind, and of course we could elaborate on the theme in various ways -- scratching for various adjustments to discomforting circumstances etc. However, Jim has a nice line in provocative ideas. I had not thought of "We have learned in recent years that children raised in a protected sterile setting often develop asthma or other improper immune responses, and that those raised on farms do better--subjected to many immune system challenges.  I wonder if scratching one's itches falls into the same category and has a value the medical profession is ignoring."

Well, I am sceptical to say the least. It might certainly happen I suppose, and there are other bodily adaptations that function as exposure of the immune system to antigens, tonsils, Peyer's patches and so on, but scratching seems a rather injurious way of achieving anything of the type. Still... the cells of Langerhans in one's skin...

Dunno. Still sceptical. All the same... Not a bad thought at all. Not that I would recommend scratching of course, but...

Dunno. But hard to test though.  Maybe exposing the skin to synthetic allergens in a double-blind exposure, some under patches that prevent scratching, some not...

Still dunno...

Well, you heard it from Jim first! Remember that when the Nobel committee comes by to make enquiries!

Still, this does not detract from my advice not to scratch mosquito bites and the like!

Any earth-shaking thoughts anyone?