Perleche

From IKE

Perleche (aka angular cheilosis, cheilitis or angulus infectiosus) is some icky shit at the corner of the mouth.

There are three major etiological factors behind angular cheilosis. Sagging facial muscles and ill-fitting dentures may aggravate or infect the side of the mouth, which is common in the elderly. Infections, such as monilia or Staphlycoccus aureus, may also be responsible. Deficiency of nutritional compounds such as riboflavin or iron are another major factor.

Rare causes include contact allergies, dermatitis, or AIDS.