Getting pimples on the back of the head after a haircut is a common phenomenon that has been experienced by many. This is because when the hair is cut, the follicles become clogged with the hair, sweat, and dirt that get trapped in the hair follicles. This clogging can cause inflammation and can lead to pimples. Additionally, the use of chemicals such as hair dye and hair styling products can also increase the risk of pimples in the back of the head. To prevent this, it is important to clean the scalp thoroughly after a haircut, and to use products that are designed for sensitive scalps.