The clinical term for the condition is called Acne Mechanica. Maskne is caused by the constant pressure, friction, rubbing, and squeezing of the skin under the mask. This rubbing creates micro-tears, allowing easier entry for dirt, sweat, and bacteria to invade your skin. Then the warm moist conditions under your mask create the perfect conditions for bacteria to thrive. The end results are red bumps and skin lesions as well as blackheads or other flareups.