Hi. My 10 year old son has the same as shown in your photo. I noticed your post was taken last year, just wondering if you'd had any help?

Hi , had this problem for about 5 years and tried almost everything and al antibiotic amoxciciline but the result was only for few days then the bumps came back more again!
What really worked for me was appelcider this is a wonder middel !!
buy bio appelcider and mix 3 spoon appelcider with cup of water and drink 1x in de morning before breakfast and 1x before you go to sleep . and before sleep smear some appelcider on your backhead and wash in de morning.
do this for at least 2 weaks.!!! When you see a good result don't stop! you can drink 1x on a day for about 6 months. Then you wil heal 100% .
and buy your ouwn tondeuse when you go to your hair stylist better use yours!

I know OP hasn't been back for a year but in case anyone else reads this:

Do you see the "track mark" pattern? How some of them appear to be clustered together in straight lines?

This is due to MITES burrowing. 

Start with tea tree oil + isopropyl alcohol 50:50 mixed, apply twice a day and let air dry

If no improvement in 2 weeks, you will need permethrin 5% applied nightly for 8 hours for 2 weeks. If still no improvement, oral ivermectin+metronidazole will clear it right up.

This is treatable. Good luck.