PHYSICAL FACTORS IN DERMATOLOGY

HEAT/BURN excessive heat on skin, divided into 3 types: 1st. Degree: only erythema with constitutional symptoms if a large area is affected. 2nd. degree: superficial type causing bullae, healing with no scarring, or deep healing by scarring. 3rd. degree: loss of full thickness skin + underlying structures healing by scarring

HEAT MILIARIA Retention of sweat as a result of occlusion of sweat duct, causing rupture of gland & escape of sweat, 3 types according to level of obstruction: 1- crystallina: in stratum corneum. 2- rubra: in prickle cell layer. 3- profunda: in upper dermis.

HEAT ERYTHEMA AB IGNE Persistent erythema or the coarsely reticulated residual pigmentation resulting from it, due to long exposure to excessive heat without burn. First transient, then permanent Legs of women May cause epithelial atypia, rarley Bowen’s disease or squamous cell carcinoma.

COLD PERNIOSIS Localised erythema & swelling caused by exposure to cold, with even sometimes blistering or ulceration. It is cold hypersensitivity. Mostly hands, feet, ears, & face in children. Onset may be enhanced by dampness Bluish red, cool to touch+ burning & itching Treatment is preventive, spontaneous recovery

COLD FROST BITE Freezing of tissue due to exposure to extremely low temperature, a form of toxic effect. Painless, pale & waxy+ various degrees of tissue damage as in burn depending on the temperature & duration of exposure. Treament is by rapid re-warming + supportive measures

SUN ACTINIC INJURY Solar spectrum has many regions according to wavelength, most important is UVL. UVA 320-400nm UVB 290-320 nm UVC 200-290 nm UVB has more than 1000 more erythmogenic effect than UVA, & is more in midday hours. Either sunburn or photosensitivity

SUN SUNBURN Normal reaction of skin to sunlight in excess of erythema dose. Erythema starts after 6 hours, peaks in 12-24 hrs. Followed by tenderness & severe cases blistering. May be associated by edema of face, limbs, fever, chills, nausea & hypotension. Desquamation follows in a week treatment: analgesics+ soothing agents

SUN PHOTOSENSITIVITY Abnormal reaction to normal sun exposure 1- Chemical photosensitivity: by photosensitizres which are either applied topically as in phytophotodermatitis, or internally by enteral or parenteral adminstrtion of drugs as in phototoxic drug reactions. 2- Metabolic: as in porphyria, & pellagra

SUN PHOTOSENSITIVITY 3- light exacerbated disorders: genetic or acquired as SLE, Darier’s, vitiligo, acne, small % of psoriasis, dermatomyositis, lichen planus actinicus, & chloasma. 4- Idiopathic photosensitivity: most common is polymorphic light eruption: onset in first 3 decades, with a ratio of 2-3: 1 ♀:♂

POLYMORPHIC LIGHT ERUPTION Different morphologies in different people Constant morphology in the same patient Mostly is papular or erythemapapular form but could be papulovesicular, eczematous, erythematous & plaque like. Healing only with dyspigmentation Mostly on sun exposed skin Starts in spring, improve in summer

TREATMENT 1- AVOIDANCE 2- TOPICAL STEROIDS 3- ANTIHISTAMINES 4-SYSTEMIC STEROIDS 5- ANTIMALARIALS 6- LIGHT THERAPY 7- IMMUNOSUPPRESSANTS

Mechanical injury callus & clavus CALLUS: circumscribed hyperkeratosis induced by pressure, diffuse with no central core. CLAVUS: (corn): circumscribed conical thickenning with base on surface & apex down pressing on subjacent structures, of 2 types: Soft corns Hard corns