They appear as small white bumps near the surface of the skin. Open comedones are visibly enlarged, clogged pores filled with dead skin cells and oil. Inflammatory Lesions Papules form when overloaded hair follicles spill their contents into the surrounding skin tissue. They appear as small bumps, and are usually red, swollen, and tender. Pustules are pus-filled, swollen pimples caused by the body's white cells attacking a clogged hair follicle.
Nodules are the most severe form of acne lesion.
Acne with nodules often results in permanent scarring and requires treatment by a physician. Sometimes called an acne 'cyst'.