Skin

"The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.
Skin has three layers: The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis."

Paronychia

Paronychia is a skin infection that occurs around the nails. Paronychia is fairly common. It is usually caused by injury to the area -- for example, from biting off or picking a hangnail or from trimming or pushing back the cuticle. The main symptom is a painful, red, swollen area around the nail, often at the cuticle or at the site of a hangnail or other injury. There may be pus-filled blisters, especially with a bacterial infection.