Anyone here get an itchy scalp when they don't wash their hair for a few days?

How many days would that be?

For me, it's 3 days. I go for more than 3 days without washing my hair and it starts itching.

What is it? Dandruff? Body oils? Dirt?
I don't know. I don't have any dandruff. And I keep my hair covered most of the time. So I'm not sure why