INVITED REVIEW ARTICLE Nagoya J. Med. Sci. 63. 83 ~ 90, 2000

CONTACT DERMATITIS RITSUKO HAYAKAWA M.D., Ph.D. Department of Environmental Dermatology, Nagoya University School of Medicine

INTRODUCTION Contact dermatitis is an inflammation of the skin induced by a contacted substances. The skin manifestation of contact dermatitis is multifarious showing erythema, edema, papules, seropapules, vesicules, bullae, erosion, crust, etc. Distinguishing subjective symptom is itching. The causes of contact dermatitis are plant, foods, animal dandruff, daily goods, cosmetics, topical applications and occupational chemicals (Table 1). Contact dermatitis is classified into 7 types by its etiological mechanism. Irritant (acute and chronic irritant type) dermatitis, photo toxic dermatitis, allergic dermatitis, photo allergic dermatitis, contact urticaria syndrome, systemic contact type dermatitis and contact dermatitis syndrome.

IRRITANT DERMATITIS Irritant dermatitis describes the effect caused by a irritation on the skin. An acute irritant dermatitis is caused by a strong irritation such as a strong alkali. Chronic irritant type dermatitis is caused after repeated insults by weak irritants over a long period. Irritants are substances that damage the skin by direct toxic action. It is difficult to assess irritant results because the reactions may be influenced by age, sex, race or the season of the year. The suitable skin testing for detecting a strong irritant is open testing. Repeated open application test is suitable for detecting weak irritant. However, for strong irritants, we should have consideration not to conduct skin testing carelessly because it may cause a strong reaction such as a chemical burn, erosion or necrosis. When we have to decide the causative agent of acute irritant dermatitis inevitably, suspected substances should be diluted in advance to the concentration that would produce a threshold irritant response (not a strong reaction) on volunteers tested. In general, the intensity of reactions to irritants is proportional to the concentration and exposure time.

PHOTO TOXIC DERMATITIS Photo toxic dermatitis occurs upon first exposure under appropriate conditions, such as sufficient intensity of light and quantity of photo toxic chemicals. Photo toxic reactions are based

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84 Ritsuko Hayakawa

Table 1. Staging of Contact Urticaria Syndrome

Fig. 1

The photo toxic dermatitis cused from a perfume

on non-immunologic mechanisms and manifest as an exaggerated sunburn reaction followed by pigmentation (Fig. 1). Window glass, which absorbs most of the ultraviolet rays, will protect patients from photo toxic reaction having an action spectrum below 320 nm.

ALLERGIC DERMATITIS Allergic dermatitis is caused as the result from exposure of sensitized individuals to contact allergens. It is a delayed hypersensitivity reaction. In its acute phase, allergic dermatitis is characterized by redness, edema, papules, vesiculation, weeping and crusting. It is accompanied by itching. If it becomes chronic, the involved skin may become thickened, lichenified and pigmented1-5) (Fig. 2). Anything surrounding people may become a cause of allergic dermatitis. Plants, foods, products used in domestic life, cosmetics, topical applications and occupational chemicals may cause allergic contact dermatitis.6-20)

85 CONTACT DERMATITICS

Erythema accompanied reticular pigmentation on the cheek Fig. 2

Patch test positive reaction from PAN

Pigmented allergic contact dermatitis due to 1-phenyl azo 2-naphtohl (PAN) in cheek rouge

Contact allergens are small-molecule substances (