What you can do differently: Wipe your face, chest, and back down before you work out with facial wipes, like Neutrogena Makeup Remover Cleansing Towelettes, to remove your makeup. Then, if you don't have time to shower immediately after the gym, use another fresh facial wipe to clear away any sweat and bacteria on your skin to minimize the chance of new pimples popping up.
Experiment with aloe vera. The sap of the aloe vera plant is a soothing natural substance which can be used to relieve many ailments, from burns to wounds to acne scars. Aloe vera helps to rejuvenate and moisturize the skin, encouraging acne scars to fade. It is possible to buy aloe vera products in the drugstore, but the best thing to do is buy an aloe vera plant and use the sap from a broken leaf. This gel-like sap can be applied directly on the scarring, and there is no need to wash off.
Drugs: Some medications may cause or worsen acne, such as those containing iodides, bromides, or oral or injected steroids (either the medically prescribed prednisone [Deltasone, Orasone, Prednicen-M, Liquid Pred] or the steroids that bodybuilders or athletes sometimes take). Other drugs that can cause or aggravate acne are anticonvulsant medications and lithium (Eskalith, Lithobid). Most cases of acne, however, are not drug related.