An ingrown hair is what occurs when a hair that's previously been removed from the follicle grows back and curls under the skin. They often look like boils or pimples (even groups of pimples) and can often hurt and leave scars if they're not properly removed. This is why many skin-care experts recommend that you exfoliate and use serums after shaving or waxing; it helps to prevent the hair from getting trapped underneath dead skin.
While ingrown hairs originate at the follicle level, pimples originate at the sebaceous oil gland and occur when excess oil gets trapped underneath the skin. They can appear red on the skin and become filled with pus. Ingrown hairs can also be filled with pus, but in many cases, you should be able to see the hair underneath the skin that caused the bump to grow in the first place.
