Rinse your face with warm water and make sure there is no makeup or moisturizer on your skin. With your finger, dab the paste onto your blemishes, and then allow it to dry. You can wait 10 minutes, a half hour, or even keep it on while you sleep. Rinse away with warm water and a washcloth, and pat your skin dry. Aspirin contains a high concentration of salicylic acid, which is a common ingredient in anti-acne products.