When the hair follicle doesn't have an opening on the surface of the skin, the sebum gets trapped inside. It appears as a white bump, which is why it is referred to as a whitehead. Macrocomedones, which are comedones that are larger than 1 mm, mostly occur on the face. People who have oily, acne-prone skin are more likely to develop blackheads or whiteheads on the forehead, nose, chin, etc. These can be removed with the help of a comedone extractor.