1. Contact Dermatitis

2. 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

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

4. 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

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

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

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

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

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

11. erythema
macule

12. erythema、edema、vesicle 、bullae

13. 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

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

17. differential diagnosis：eczema，erysipelas

19. differential diagnosis：eczema，erysipelas

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

21. 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 %boracic acid 、R.R fluid
subacute Neomycin-coal tar paste
soakage and thick %-5% Neomycin-coal tar cream、

22. Ⅳ systemic therapy
antihistamines
corticoid