The Pores in our skin are follicles which may or may not contain a hair, through which natural sebum (skins natural oil secretion) flows. The amount of sebum which flows out of the follicle will depend on its size. When there is excessive sebum within the Sebaceous gland (which produces the sebum) it may swell and the follicle will become enlarged. Some follicles are naturally larger but this is due to your genetic make up.
The follicle can become blocked due to a build up of sebum, dead skin cells and bacteria which over time will cause an impacted sticky plug which we call a comedone (blackhead). The comedone will also cause the follicle to become enlarged. Once a comedone has developed the only way to remove it from the follicle is to perform an extraction.
The best treatment for enlarged pores and comedones is prevention, by always thoroughly cleansing and regular exfoliation. By doing this you will be enabling the follicle to function normally by preventing a build up of dead skin cells, sebum and bacteria.