Question: why do we itch

Luke Humphrey answered on 14 Apr 2025:

Great question! I don’t know much about this, but on a basic level the reason we itch is probably for sweeping away dangerous things like venomous insects. If you feel something on your skin, you get an urge to scratch it, which likely removes the insect before it can do more damage, and you feel some relief as part of the body’s reward system.

But it’s interesting how we can itch from many other things as well. And a lot of the time, scratching an itch can actually do more damage if you tear the skin or disrupt the healing process.

I’ve actually recently been to the vets because my dog had some skin infections. It turns out he has allergies which were making him itchy, which caused him to scratch until his skin and fur were damaged, which led to the infection. Skin & fur act as a barrier to infection; so it’s very interesting that what should be a protective instinct to scratch away dangerous things can turn into a danger in itself.

His recovery is going very well (just so you’re not worrying). One of the medications he’s on now is specifically to reduce the itchiness and it’s been very effective. He stopped scratching within hours and his injuries healed in a few days!

I’d love to hear more from any biologists on here who might know more about why we itch even when it can be harmful to us.