It seems like you have Scalp Folloculitis,which is an inflammatory condition of the hair follicles or roots.
The condition can be caused by friction,bacteria or yeast or one of the more together.
Therefore I think you need to have the following treatment.
1: fusidic acid
gel,this is an anti biotic and should be applied to the lesions directly two times a day for 7-14 days.
2: some dermatologists also suggest an application of topical steroids
only once at night as there is is an element of inflammation involved.
AD shampoo,use the shampoo two times a week to clear of the skin from fungal infection
for 4 weeks.
4: you can also try Tablet Zyrtec
10mg once a day for 2 weeks.
I think this is the best possible OTC treatment for your problem but if this condition doesn't cleared in 10-14 days time then you need to see a dermatologist or your GP to have a look at it live.
I hope this will help.