I just realized recently that after wearing a beanie (all types…polyester, cotton etc.) for a long period, my head becomes all sensitive. My brother experienced this too…and hypothesized that because the hair follicle is ‘pushed’ into one direction for so long, it becomes sensitive. It made me think…perhaps they (hair follicles) are really fragile? But then I think…this never happens when I wear a regular hat…do you have any idea why this happens?
Many of the Jewish faith wear yarmulkes, and the Pope wears a zucchetto (both are skullcaps), and they keep it on most of the time. These are loose fitting and non-constricting. If your beanie is tight, then maybe it is putting pressure on the peripheral nerves and causing your problem. I do not believe that there is any connection to the fabric, because you have used caps with different fabrics and still experience the same reaction. I don’t really have an answer for you, unfortunately, except for the too tight explanation, but you know how tight it is on your head. Covering part or all of the head is essentially the same, whether with a skullcap, beanie, or even a baseball cap.