Heat and cold
Skin changes due to cold
Acrocyanosis is the name given to mottled cool peripheries with cyanosis (blue discolouration) or erythema (reddened skin). It predisposes to chilblains.
Chilblains arise because of localised cold injury in exposed areas (most often fingers, toes, ears). They present with erythema, cyanosis, oedema (swelling), blisters and ulceration. The lesions usually heal within several weeks as long as there is no further exposure to significant cold. Severe pernio may be the presenting sign of connective tissue disease, especially systemic lupus erythematosus (chilblain lupus) or systemic sclerosis. However, they are also an occupational hazard for dairy farmers, fishermen and other outdoor workers.
Severe cold injury can damage the small bones in the digits, leading to microgeodic disease, swelling and sometimes, bone fracture.
Prevention of chilblains requires keeping the digits and ears warm and dry. A vasodilator medicine such as oral nifedipine may be helpful.
The term Raynaud's disease refers to primary Raynaud's. Secondary Raynaud's is associated with many underlying diseases especially systemic sclerosis.
Characteristically, painful attacks follow exposure of the digits to cold. They become white then in turn cyanosed and erythematous before returning to a normal colour.
Frostbite is due to severe cold injury (temperatures below freezing). Early signs are blanching and numbness.
Treat areas exposed to severe cold by rapid re-warming in water bath at 40° (providing no risk of further re-freezing). Late sequelae include pain, numbness, cold sensation, hyperhidrosis (excessive sweating), dystrophic nails (damaged nails), fibrosis (scarring), osteoporosis (weak bones) and cold intolerance.
Cryoglobulinaemia is a condition in which there are proteins circulating in the blood stream that may solidify in cold conditions. Cold-precipitable proteins are deposited in cool areas (ears, toes, fingers). Cryoglobulinaemia may present as livedo reticularis or superficial infarction.
Cold urticaria is a rare type of physical urticaria (hives from an external physical event) that arises during re-warming after cold exposure. The more common acquired variety usually affects children and young adults.
Wheals may affect any site, most often face and exposed sites. The wheals persist for up to two hours (or longer, in the rare inherited form of cold urticaria). Cold urticaria may result in anaphylactoid symptoms e.g. on swimming in cold water.
Skin changes due to heat
Erythema ab igne
Erythema ab igne is due to local heat such as a hot water bottle or sitting close to fire. It presents as erythema in a vascular distribution and is often followed by postinflammatory pigmentation. No treatment is effective but the appearance improves with time.
Erythromelalgia results in burning pain when feet or hands are warm. Affected areas are erythematous or cyanotic. Some cases are associated with polycythaemia, thrombocythaemia or lupus erythematosus. In these secondary cases, symptoms may respond to low-dose aspirin.
Cholinergic urticaria is caused by heat, emotional stress and exercise. The mechanism is uncertain as whealing may occur without sweating. It usually presents with numerous pruritic 2-3mm wheals surrounded by a red flare, which persist for 15 to 30 minutes and are at least sometimes associated with exercise. Treatment may include oral antihistamines, phototherapy, propanolol or scopolamine with variable efficacy.
Excessive eccrine secretion (sweat) or hyperhidrosis may be generalised or localised (most often to hands, feet, axillae and/orface). Most cases present in adolescence or young adult life and appear to be due to idiopathic hypothalamic stimuli. Hyperhidrosis is rarely due to systemic disease such as hyperthyroidism or hypothalamic disease, when it is more likely to present later in adult life.
Hyperhidrosis is aggravated by thermal, emotional or gustatory (taste) stimulae. It may result in bromhidrosis (malodour) and occupational difficulties. All patients should use medical grade antiperspirant lotions, which contain aluminium chloride hexahydrate. Other treatments include iontopheresis, oral probantheline, propranolol, intradermal botulinum toxin, axillary liposuction or excision of affected skin, or in severe cases, sympathectomy.
Miliaria refers to sweat rash (prickly heat) due to obstructed sweat glands and perhaps localised hyperproliferation of specific commensal microorganisms such as strains of Staphylococcus epidermidis. It presents with non-follicular superficial papules, vesicles or pustules mainly arising on the trunk. Treatment requires cooling; calamine lotion may be soothing.
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