Microcomedone. A comedone that is formed below the epidermis and can’t be seen by the naked eye. It feels like a small, hard bump and, as it grows larger, it looks like a tiny white bump just below the surface of the skin.
Closed comedo (whitehead). A firm white papule.
Open comedo (comedones). A hard plug composed of sebum and dead skin cells. This is the mildest form of acne.
Papule. An inflamed lesion that is a small, solid and slightly raised area of the skin less than half of an inch in diameter. It can have a varied appearance, such as rounded, smooth or rough, skin-colored or red, pink or brown.
Milia. Also known as epidermal cysts, these are small, firm, white papules usually found in clusters on the upper cheeks and around the eyes.
Pustule. A small pus-containing skin blister often found at the opening of hair follicles, this inflammation is more visible than a papule.
Nodule. A large, painful, solid lesion that extends deep into the skin.
Cysts. In some cases, a membrane entraps the infection and a cyst forms. Cysts are inflamed pus-filled lesions.