I have a cluster of reddish type bumps on the back of my neck. I have had it for about 4 days now. It showed up two days after getting a hair cut. My barber does use a clipper and a razor to shape up the back hair line but the bumps are not all across the hair line but rather just in a few places. I have been going there for years and this has never happened.
I am not prone to acne. I actually pretty much never get any at all. It itches a little.
I did sleep over at a friends house the day after I got the hair cut so I don't know if it could be something else like the pillow.
I only have seasonal allergies.
I did not take a shower right after getting a hair cut but did about 4-6 hours later.