Acne is caused by dirt.

Wrong!  Acne is caused a number of things, but dirt isn’t normally one of them. Acne blemishes form when dead skin cells mix with your body’s natural (sebum) oil, forming a plug in the hair follicle. Dirt may play a role in clogging the follicle but more often than not, the culprit of the plugged pore is "scale" or dead skin cells that slough off the inner lining of your hair follicle.  Because dirt is not causing your acne, overwashing your face or body (more than 2–3 times per day) will not make your it better.  In fact, too much washing or overuse of harsh scrubs and “pore strips” can actually strip the skin of the oil it needs to stay soft and pliable.  In fact, overwashing may stimulate your skin to create more oil, thereby worsening the problem.