That level of itching seems to indicate a whole 'nother issue to me. Seems it might need a different solution than a helmet that only addresses a symptom of the problem (access to scratch).
I always wear a cap for big deflection and sweat absorbtion. All year long.
You wear them?
You bald (my top is, sides are barely there)?
If bald, maybe try lotion pre ride and wear cap.
It doesn’t itch till the helmets on and i’m riding…but yeah one big itch per 30min or so.
It’s probably due to sweating, dry skin, head shape, and air hitting one spot and not another spot.