ziggo,

I would think that a simple explanation of your head sensitivity should help greatly. I have a large mole on my scalp. Back when I was getting short hair cuts, I needed to tell the barber or they would nick it with the clippers. They always appreciated my instruction. They will even recognize me and ask me to point it out when I return for another haircut.

If you can work your own hands over your head to determine how you respond to touch, you can explain how you can tolerate touch to your head. The barber will appreciate your instructions because they do not want to cause pain. The more you can state this objectively rather than with a winy 'woe is me' attitude, the more likely the person will be very supportive of your needs.

You may need to be aware that vibrating clippers will have a different and more severe risk of discomfort.

I hope you have a good experience.

My best to you.

Stating the facts rather than emotional pleas has usually worked well for me.