A closed comedo, or more commonly known as a whitehead, that has been blocked with sebum causes blind pimples to form, according to Brownstone Dermatology Associates. Oil and bacteria can also clog pores and cause blind pimples, and the appearance of closed comedones is often associated with puberty, menstruation and pregnancy.
The blockage of pores that results in closed comedones is common in areas of the face that are excessively oily such as the chin, nose and forehead. A range of treatment options are available like using a prescription topical ointment or by applying benzoyl peroxide, according to Healthline. Additionally, it may take anywhere from 6 to 12 weeks of treatment before results are noticeable, and it is necessary to continue treatment after the blind pimples clear up to ensure they do not return, notes Brownstone Dermatology Associates.