What causes milia in the hair-touching area?

I keep getting tiny pimples repeatedly only on the nape of my neck and along my jawline where my hair brushes.

I would like to know why breakouts persist only in this specific area. Is it because my hair constantly touches and irritates my skin? I am also curious if shampoo or conditioner ingredients remain on my neck and chin without being properly rinsed out during washing, causing the breakouts. I would like to know if the physical friction caused by high-necked collars or hair brushing against this area is also a contributing factor. I would be very grateful if you could provide detailed information on specific prevention methods and care tips to get rid of these small bumps, such as whether I should change the order in which I wash my hair or cut it.