Acne scars are usually the result of inflamed blemishes caused by skin pores engorged with excess oil, dead skin cells and bacteria. The pore swells, causing a break in the follicle wall. Shallow lesions are usually minor and heal quickly. But if there is a deep break in the wall of the pore, infected material can spill out into surrounding tissue, creating deeper lesions. The skin attempts to repair these lesions by forming new collagen fibers. These repairs usually aren't as smooth and flawless as the original skin.