250x250px Burning: two days after second-250x250px Chemical exposure: 250x250px A<unk>  may form when the skin has been damaged by friction or rubbing, heat, cold or chemical exposure. Fluid collects between the upper layers of skin (the epidermis) and the layers below (the dermis). This fluid cushions the tissue underneath, protecting it from further damage and allowing it to heal. Friction Intense rubbing can cause a<unk> , as can any friction on the skin if continued long enough. This kind of<unk>  is most common after walking long distances or by wearing old or poorly fitting shoes.<unk> s are most common on the hands and feet, as these extremities are susceptible while walking, running, or performing repetitive motions, such as joystick manipulation whilst playing certain video games, certain sports (e.g., baseball pitching), digging with a shovel, playing guitar or bass, etc.<unk> s form more easily on damp skin than on dry or soaked skin, and are more common in warm conditions. Less-aggressive rubbing over long periods of time may cause calluses to form rather than a<unk> . Both<unk> s and calluses can lead to more serious complications, such as foot ulceration and infection, particularly when sensation or circulation is impaired, as in the case of diabetes, neuropathy or peripheral artery disease (PAD). Burning This type of<unk> ing is one of the tools used to determine the degree of burns sustained. First and second degree burns may result in<unk> ed skin; however, it is characteristic of second degree burns to<unk>  immediately, whereas first degree burns can have<unk> s after a couple of days. Sunburn can also result in<unk> s.<unk> s can also form on the hands and feet as a result of tissue damage incurred by frostbite. Chemical exposure Sometimes, the skin will<unk>  when it comes into contact with a cosmetic, detergent, solvent, or other chemical such as nickel sulfate, Balsam of Peru, or urushiol (poison ivy, poison oak, poison sumac). This is known as contact dermatitis.<unk> s can also develop as a result of an allergic reaction to an insect bite or sting. Some chemical warfare agents, known as<unk>  agents or vesicants, cause large, painful<unk> s wherever they contact skin; an example is mustard gas. Blood<unk>  A blood<unk>  usually forms when a minute blood vessel close to the surface of the skin ruptures (breaks), and blood leaks into a tear between the layers of skin. This can happen if the skin is crushed, pinched or aggressively squeezed. Medical conditions There are also a number of medical conditions that cause<unk> s. The most common are chickenpox, herpes, impetigo, and a form of eczema called dyshidrosis. Other, much rarer conditions that cause<unk> s include: * Bullous pemphigoid: a skin disease that causes large, tightly filled<unk> s to develop, usually affecting people over the age of 60. * Pemphigus: a serious skin disease in which<unk> s develop if pressure is applied to the skin; the<unk> s burst easily, leaving raw areas that can become infected. * Dermatitis herpetiformis: a skin disease that causes intensely itchy<unk> s, usually on the elbows, knees, back and buttocks. The<unk> s usually develop in patches of the same shape and size on both sides of the body. * Chronic bullous dermatosis: a disease that causes clusters of<unk> s on the face, mouth or genitals. * Cutaneous radiation syndrome * Epidermolysis bullosa
Blister
Oscar 
Saddle sore
Sequela
Pouchitis
Phlegmon
Chilblains
Eschar