Contact Dermatitis

Definition An inflammatory reaction resulting from interaction of an external substance with the skin. Usually cause acute eruption Erythema,macules,vesicles,bullae,even necrosis Itch or burn

Etiology and pathogenesis chemical、biological、physical or mechanical irritant Chemical substances are more important

Ⅰ Primary irritant dermatitis Substances directly irritant dermatitis Chemical or physical concentration variation from time to time Weat irritant exposed repeat eruption Strong acids, alkalis, mustard gas from minutes to hours dermatitis

Ⅱ Allergic contact dermatitis delayed type hypersensitive reaction 1． atopic 2． Exposure 3． latent period 4-20d(first contact)，reexposed 12-48hr 4． Hardening

hapten +protein of epidermis (holoantigen) activation IL-2R INF- TNF-  LC Th1 Th1 inflammation IL-2 proliferation

Allergen： ①animality ②plant ③cosmetic and topical drugs ④pesticide ⑤metals and metal salts ⑥industrial materials and products

Ⅲ phototoxic or photoallergy Phototoxic dermatitis photoallergic dermatitis sunlight Chemicals + skin （photosensitizer）

clinical character、concentration、exposed time susceptivity Early stage： erythema macules、edema 、 vesicles 、 bullae 、 necrosis continuous exposure dry 、soakage、thickened、 lichenoid、fissure Weak irritant

erythema macule

erythema、edema、vesicle 、bullae

area：clear border， high sensitivity or itch Lesion position area：clear border， high sensitivity or itch wide bound、border not clear eyelid、pudendum edema scalp infection symptom：itch、cautery feeling、 pain Course of disease：1-2weeks

differential diagnosis diagnosis and differential diagnosis history acute eruption lesions in contact position unitary、clear edge patch test/photopatch test

differential diagnosis：eczema，erysipelas

differential diagnosis：eczema，erysipelas

Therapy Ⅰ finding irritating and sensitizing substances Ⅱeliminating contact of the skin

diminish inflammation、stop itch、prevent secondary infection Ⅲ topical therapy： diminish inflammation、stop itch、prevent secondary infection acute stage without exudation surge lotion、hydropathic compress glucocorticoid cream erosion and exudation hydropathic compress （3%boracic acid、Aluminum acetate compound ） infection 3%boracic acid 、R.R fluid subacute Neomycin-coal tar paste soakage and thick 2%-5% Neomycin-coal tar cream、

Ⅳ systemic therapy antihistamines corticoid