Contact Contact DermatitisDermatitis

DefinitionDefinition

An inflammatory reaction resulting frAn inflammatory reaction resulting from interaction of an external substanom interaction of an external substance with the skin.ce with the skin.

Usually cause acute eruptionUsually cause acute eruption Erythema,macules,vesicles,bullae,eveErythema,macules,vesicles,bullae,eve

n necrosisn necrosis Itch or burnItch or burn

Etiology and pathogenesis

chemical 、 biological 、 physical or mechanical irritant

Chemical substances are more important

Ⅰ Ⅰ Primary irritant Primary irritant dermatitisdermatitis

Substances directly irritant dermatitis Substances directly irritant dermatitis Chemical or physical concentrationChemical or physical concentration variation from time to time variation from time to time Weat irritant exposed repeat eruptWeat irritant exposed repeat erupt

ionionStrong acids, alkalis, mustard gas from Strong acids, alkalis, mustard gas from

minutes to hours dermatitisminutes to hours dermatitis

Ⅱ Allergic contact dermatitis delayed type hypersensitive reaction

1 ． atopic

2 ． Exposure

3 ． latent period 4-20d(first contact) ， reexpo

sed 12-48hr

4 ． Hardening

hapten +protein of epidermis

(holoantigen)

LCINF-TNF-

inflammation

Th1 Th1

activation

IL-2

IL-2R

proliferation

Allergen ：①animality②plant③cosmetic and topical drugs④pesticide⑤metals and metal salts ⑥industrial materials and products

Ⅲ phototoxic or photoallergy

Chemicals + skinsunlight

（ photosensitizer ）

Phototoxic dermatitis photoallergic dermatitis

clinical

susceptivitycharacter 、 concentration 、exposed time

Early stage ： erythema macules 、 edema 、 vesicles vesicles 、 bullae bullae 、 necrosisnecrosis

Weak irritantcontinuous

exposure

dry 、 soakage 、 thickened 、lichenoid 、 fissure

erythemamacule

erythema 、 edema 、 vesicle 、 bullae

scalp infectionsymptom ： itch 、 cautery feeling 、 painCourse of disease ： 1-2weeks

Lesion position area ： clear border ， high sensitivity or itch

wide bound 、 border not clear

eyelid 、 pudendum edema

diagnosis and differential diagnosis

historyacute eruptionlesions in contact position unitary 、 clear edgepatch test/photopatch test

differential diagnosis ： eczema ， erysipelas

differential diagnosis ： eczema ，erysipelas

Ⅰ finding irritating and sensitizing substances

Ⅱeliminating contact of the skin

Therapy

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 、 glucocorticoid cream

Ⅳ systemic therapy

antihistamines

corticoid