Phytophotodermatitis Health Dictionary

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Phytophotodermatitis: From 1 Different Sources

n. an eruption of linear blisters occurring after exposure to light in people who have been in contact with certain plants, such as wild parsnip or cow parsley, to which they are sensitive. A particularly dramatic reaction occurs with giant hogweed (Heracleum mantegazzianum). The skin often appears brown as the blisters resolve.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Photodermatoses

Diseases of the SKIN for which sunlight is partially or wholly responsible. In su?cient dosage, short-wave ultraviolet light (UVB – see ULTRAVIOLET RAYS (UVR)) always causes ERYTHEMA. Higher doses progressively cause OEDEMA and blistering; this is acute sunburn. Graduated exposure to UVB causes pigmentation (tanning). Prolonged chronic exposure to sunlight eventually accelerates ageing of the exposed skin with LENTIGO formation and loss of COLLAGEN and elastic tissue. After decades of such exposure, epidermal DYSPLASIA and CANCER may supervene.

Drugs given orally or topically may induce phototoxic reactions of various types. Thus, TETRACYCLINES exaggerate sunburn reactions. and the diuretic FRUSEMIDE may cause blistering reactions. Psoralens induce erythema and pigmentation. AMIODARONE also induces pigmentation. (See also PHOTOCHEMOTHERAPY.)

Phytophotodermatitis is a streaky, blistering photodermatosis typically seen on the limbs of children playing in grassy meadows in summer. The phototoxic reaction is caused by psoralens in weeds.

Berlocque dermatitis is a pattern of streaky pigmentation usually seen on women’s necks, caused by a reaction to psoralens in perfumes.

Certain rare metabolic diseases may lead to photosensitisation. They include the PORPHYRIAS and PELLAGRA. Other skin diseases such as lupus erythematosus (see under LUPUS) and ROSACEA may be aggravated by light exposure. Sometimes, in the absence of any of these factors, some people spontaneously develop a sensitivity to light causing various patterns of DERMATITIS or URTICARIA. The most common pattern is ‘polymorphic light eruption’ which typically appears within a day or two of arrival at a sunny holiday destination and persists until departure. Continuously exposed areas, such as the hands and face, may be ‘hardened’ and unaffected.

Treatment Appropriate clothing and headgear, sunscreen creams and lotions are the main preventative measures.... photodermatoses


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