So I have a few scrapes that turned to scabs recently and while absent-mindedly scratching them, I remembered the first time I found out why scabs itch.
There are actually a number of reasons theorised for the itching sensation. I’ll give the two most plausible ones.
First of all, there are tiny nerves in the upper layers of your skin that can send tickling sensations to your brain. When the skin is torn, the healing process may cause these nerves to send signals (like testing to see whether everything is working), which your brain misinterprets as itching. Also, as the wound heals, the scab pulls away from the skin gradually, further stimulating these nerves.
Second, scabs contain histamines which irritate the surrounding area of skin. It’s said that the histamines are there so to help the process – so that when the wound is fully healed, you’ll just scratch it off. Unfortunately, the itching begins long before it’s ready to remove the scab.