From MedlinePlus Genetics
Hailey-Hailey disease, also known as benign chronic pemphigus, is a rare skin condition that usually appears in early adulthood. The disorder is characterized by red, raw, and blistered areas of skin that occur most often in skin folds, such as the groin, armpits, neck, and under the breasts. These inflamed areas can become crusty or scaly and may itch and burn. The skin problems tend to worsen with exposure to moisture (such as sweat), friction, and hot weather.

The severity of Hailey-Hailey disease varies from relatively mild episodes of skin irritation to widespread, persistent areas of raw and blistered skin that interfere with daily activities. Affected skin may become infected with bacteria or fungi, leading to pain and odor. Although the condition is described as "benign" (noncancerous), in rare cases the skin lesions may develop into a form of skin cancer called squamous cell carcinoma.

Many affected individuals also have white lines running the length of their fingernails. These lines do not cause any problems, but they can be useful for diagnosing Hailey-Hailey disease.  https://medlineplus.gov/genetics/condition/hailey-hailey-disease