The first affiliated hospital of zhengzhou university subject Dept. of Dermatolog The First Affiliated Hospital of Zhengzhou University content
Dermatology and venerology Teaching way
grade
Oversea student
multimedia
class hour
Contact Dermatitis,, Atopic Dermatitis
Objective To master the clinical features, diagnosis of contact dermatitis and atopic dermatitis Key cocept Contact Dermatitis Clinical Features and Diagnosis History: contacting irritating and allergic agents Signs –Patches or plaques with angular corners, geometric outlines, and sharp margins –The skin lesions are usually restricted to contact sites Atopic dermatitis (AD) Etiology: Genetics of atopic dermatitis, Allergens, Immunological aspects Clinical Features and Diagnosis
2
Course of dermatology
Contact Dermatitis Miao Qing Dept. Of dermatology the first teaching hospital , zhengzhou university
Contact Dermatitis Definition – there are two types of dermatitis caused by
substances coming contact with the skin: irritant dermatitis and allergic contact dermatitis.
Contact Dermatitis
– irritant contact dermatitis is an inflammatory
reaction in the skin resulting from exposure to a substance that causes an eruption in most people who come in contact with it.
Contact Dermatitis – Allergic contact dermatitis is an acquired sensitivity to various
substances that produce inflammatory reaction in those ,and only those , who have been previously exposed to the allergen.
Irritant contact dermatitis Definition – dermatitis caused by exposure to a substance which
has a damaging effect on the normal barrier function of the epidermis.
Irritant contact dermatitis Etiology – alkalis (soaps , detergents, ammonia preparations,
lye, drain pipe cleaners, toilet bowl cleaners ) – acids ( hydrochloric acids, sulfuric acids and nitric
acids, phenol, acetic acid ) – other irritants ( metal salts----calcium, copper,
nickel, silver and zinc)
clinical features irritant
contact dermatitis may be:
acute
subacute
chronic
Irritant contact dermatitis – acute irritant contact dermatitis is seen after one single ,
usually accidental, exposure to a strong skin irritants such as acid, alkali, phenol. The onset is rapid and lesions appears exactly at the sites of contact.
Irritant contact dermatitis
Subacute irritant contact dermatitis : there is ongoing irritation as in infantile napkin dermatitis.
Chronic irritant contact dermatitis: a classic example of cumulative exposure to a mild cutaneous irritant is “washer woman,s hands” due to continual contact with detergents and alkalis. damage then develops.
Chronic skin
Clinical features Acute
irritant contact dermatitis
– after exposure to a strong irritant the affected skin becomes reddish--brown and vesicles develop. The lesions appear rapidly , usually within 6~12 hours of contact, and are painful and itchy.
Clinical features
Subacute irritant contact dermatitis: there is erythema with crusting and sometimes blistering.
There may
also be early acanthosis and skin thickening.
Irritant contact dermatitis
Chronic irritant contact dermatitis tends , initially, to present as dry, fissured areas of skin which are susceptible to secondary infections. This is seen typically in housewives and young mothers whose hands are repeatedly exposed to soap, detergents, and water.
Treatment
Identification of the irritant and its subsequent avoidance is the cornerstone of successful therapy. The cause is identified on the patients history. For the active phase, a topical steroid cream or ointment is usually the most appropriate treatment. If the lesions are acute with vesicles and weeping , wet dressing applied as lotions may be needed until the subacute phase is reached, when topical steroids can be substituted. The choice of topical steroid for the subacute phase is wide , relatively strong steroid is justified.
Treatment
Children with napkin dermatitis should have all napkins removed and be nursed in a warm dry environment with the skin exposed. Lesions will rapidly resolve if this is done and improvement will be accelerated by the use of a mild steroid antifungal combination . The management of chronic is protection of the area involved , mostly commonly the hands, from exposure to the cause and the liberal use of emollients to replace the lipid barrier.
Allergic contact dermatitis Definition – dermatitis caused by prior exposure to an allergen
leading to specific cell-mediated sensitization.
Allergic contact dermatitis Prevalence
and etiology
– this form of dermatitis affects 1~2% of the
population. Certain groups patients are at greater risk. – Allergic contact dermatitis results when an allergen
comes into contact with previously sensitized skin. – The allergens are extremely varied and may be
nonprotein in nature. Many substances , such as
Allergic contact dermatitis Prevalence
and aetiology
– dyes and their intermediates , oils, resins, coal tar
derivatives, chemicals used for fabrics, rubbers, cosmetics , insecticides, as well as the products or the substances of bacteria, fungi, and parasites, are proven allergens. – These substances do not cause demonstrable skin
changes on first contact but may produce specific changes in the skin when the patient is reexposed to the allergen at a subsequent time.
Pathogenesis of allergic contact dermatitis
Allergic contact dermatitis ( ACD ) results when an allergen comes into contact with previously sensitized skin . ACD results from a specific acquired hypersensitivity of the delayed type, also known as cell-mediated hypersensitivity or immunity .
The Langerhans cells might play a major role in the pathogenesis of contact allergy .
Clinical features ACD usually presents with acute or subacute
dermatitis lesions at sites where the allergen is , or has been , in contact with the skin and also with milder involvement of more distant areas where there has been no obvious direct contact . In the early stages the affected area is inflamed and itchy , with papules and vesicles. Continued exposure to the allergen will lead to dryness , scaling ,and fissuring. The lesions frequently spread well beyond the area of contact with the allergen and also even to distant body sites which have not been in contact with the allergen.
Regional predilection Head
and neck
– the causes may be hair dye, hair spray, shampoo. – The forehead of a man may be the site of a hat
-band dermatitis. – Perfume dermatitis may cause redness just under
the ears. – Nickel sensitivity may be noted at the clasp site of
necklaces or earings.
Regional predilection Arms
the wrists may be involved because of jewelry or the backs of watches and clasps, all of which may contain nickel.
Hands
Typically occurs on the backs of the hands and spares the palms. Poison ivy and other plant
may be the causes.
Differences between direct irritant and allergic contact
Prevalence Prior exposure to substance Affected sites
Direct irritant Very common
Allergic contact Much less common
Not required Essential Sites of direct contact Sites of contact with little extension and distant sites Susceptibility Everyone susceptible Only some patients susceptible Timing Rapid onset 4~12 hours Onset generally 24 h after contact or longer after exposure Lesions develop at first No lesions on first exposure exposure
Allergic contact dermatitis Erythema at contact sites
Allergic contact dermatitis
erythema 、 edema
Allergic contact dermatitis Erythema 、 papules at contact sites
Allergic contact dermatitis
Erythema and papules at contact site
Allergic contact dermatitis
Erythema and edema at contact site
Allergic contact dermatitis Erythema and papules at contact site
Allergic contact dermatitis
Red patch and scales at contact sites
Allergic contact dermatitis
Red patch at contact sites
Allergic contact dermatitis Erythema and edema 、 blister and oozing at contact sites
Allergic contact dermatitis Erythema and edema at contact sites
Allergic contact dermatitis
erythema 、 blister and bulla at contact sites
Irritant contact dermatitis Erythema and erosion ， strange shape
Diagnosis
history of contact substances.
Clinical features : inflammatory reaction at the sites that contact with the substances.
pruritus or
itching
or pain.
Self-limited course, when the allergens removed.
Assistant examination : patch test positive.
Treatment
The management of ACD is divided logically into four stages.
1. Detection of the likely sensitizing agent by taking a careful occupational ,recreational ,and medicament history. 2. Preparation for valid patch testing to identify the allergen. 3.Patch testing to the suspected substances . 4.Counselling on avoidance of responsible allergens following patch testing results.
Treatment Systemic
therapy
– corticosteroids : the acute stage of severe contact dermatitis
characterized by blistering, swelling and oozing is best managed with adequate doses of systemic corticosteroids. Eg: Prednisone 60~100 mg initially . – antihistamines
topical
therapy
– corticosteroids are the only rational medicaments for
therapy of contact dermatitis. Eg: cream pevisone, cream Eloson.
Differential Acute eczema
Etiology complex
diagnosis
Contact dermatitis simple
Affected sites widely affected , usually symmetric, unclear boundary
Shapes of lesions multiforms ,erythema\blister\papules\oozin g Duration usually relapse
restricted to contact sites Clear boundary
Simply shape , erythema and bulla Short , when elimination of contact
Differential diagnosis