Microcomedones (pictured below) quickly develop into comedones. Comedones are oil producing follicles that get filled with dirt, oil, tiny hairs, dead skin cells, and bacteria.
When the comedone is open or larger, sebum oxidizes and turns black. This results in the appearance of blackheads, which are very small, long-lasting black blemishes on the skin that cannot be washed away.
When the comedone is closed or very narrow, trapped sebum and bacteria remain below the skin, which results in infection under the skin. This leads to inflammation, redness, and irritation, and ultimately results in the appearance of a whitehead. Whiteheads are typically very tiny white dots, sometimes invisible to the naked eye.