First degree
First degree frostbite is superficial, surface skin damage that is usually not permanent. Early on, the primary symptom is loss of feeling in the skin. In the affected areas, the skin is numb, and possibly swollen, with a reddened border. In the weeks after injury, the skins surface may slough off. Second degree
In second degree frostbite, the skin develops clear blisters early on, and the skins surface hardens. In the weeks after injury, this hardened, blistered skin dries, blackens, and peels. At this stage, lasting cold sensitivity and numbness can develop. Third degree
In third degree frostbite, the layers of tissue below the skin freeze. Symptoms include blood blisters and "blue-grey discoloration of the skin". In the weeks after injury, pain persists and a blackened crust (eschar) develops. There can be longterm ulceration and damage to growth plates. Fourth degree
In fourth degree frostbite, structures below the skin are involved like muscles, tendon, and bone. Early symptoms include a colorless appearance of the skin, a hard texture, and painless rewarming. Later, the skin becomes black and mummified. The amount of permanent damage can take one month or more to determine. Autoamputation can occur after two months. Causes
Risk factors
The major risk factor for frostbite is exposure to cold through geography, occupation and/or recreation. Inadequate clothing and shelter are major risk factors. Frostbite is more likely when the bodys ability to produce or retain heat is impaired. Physical, behavioral, and environmental factors can all contribute to the development of frostbite.
Notalgia paresthetica or Notalgia paraesthetica (NP) (also known as "Hereditary localized pruritus", "Posterior pigmented pruritic patch", and "subscapular pruritus") is a chronic sensory neuropathy. Notalgia paresthetica is a common localized itch, affecting mainly the area between the shoulder blades (especially the T2–T6 dermatomes) but occasionally with a more widespread distribution, involving the shoulders, back, and upper chest. : 402  The characteristic symptom is pruritus (itch or sensation that makes a person want to scratch) on the back, usually on the left hand side below the shoulder blade (mid to upper back). It is occasionally accompanied by pain, paresthesia (pins and needles), or hyperesthesia (unusual or pathologically increased sensitivity of the skin to sensory stimuli, such as pain, heat, cold, or touch), which results in a well circumscribed hyperpigmentation of a skin patch in the affected area. Causes
The correlation of notalgia paresthetica localization with corresponding degenerative changes in the spine suggests that spinal nerve impingement may be a contributing cause. According to Plete and Massey, "The posterior rami of spinal nerves arising in T2 through T6 are unique in that they pursue a right-angle course through the multifidus spinae muscle, and this particular circumstance may predispose them to harm from otherwise innocuous insults of a varied nature." Patients may have other conditions that predispose them to peripheral neuropathies (nerve damage).The causes of this condition have not yet been completely defined. Patients are usually older persons. Diagnosis
Treatment
Therapy for notalgia paresthetica is directed at controlling symptoms, as no cure exists for the condition.