Allergic contact dermatitis has a distribution limited to one area of the body corresponding to contact with the allergen.The lesions generally make bizarre, linear, square, or angulatedshapes corresponding to the source. Nickel dermatitis is common and results from contact sensitization to nickel in metals. It occurs in characteristic locations, such as the periumbilicalarea (where metal from pant buttons rub against skin); onthe ear lobule or neck (where earrings contact skin); circumferentially around the neck (necklaces); and under rings or wristbands. Patients with atopic dermatitis can have concomitant contact dermatitis as well.
Figure 190-2 Atopic dermatitis with Staphylococcus superinfection.
Ideal therapy for atopic dermatitis includes three main components: frequent liberal use of bland emollients to restorethe skin barrier, avoidance of triggers of inflammation, and use of topical anti-inflammatory medication to affected areas of skin when needed. Control of pruritus and infection should be considered on an individual basis. If topicaltherapy and these measures are inadequate, systemic therapywith immunosuppressive agents or ultraviolet light therapy may be indicated.
A daily short bath with warm but not hot water is generally recommended, although this is controversial and there are some who advocate less frequent bathing. A moisturizing cream or ointment should be applied to the entire body immediately afterward to trap moisture. Application of topical medications is also most effective immediately after bathing. Additional information for patients and families can be found at the website of the National Eczema Association for Science and Education ( http://www.nationaleczema.org
Common triggers of inflammation in atopic dermatitis include rubbing or scratching, contact with saliva or foods that are acidic, soaps and detergents, fabric softeners, wool or other harsh materials, fragranced personal care products, sweat, highly chlorinated pools, low humidity, tobacco smoke, dust mites, animal dander, environmental pollens, and molds. Exposure to these triggers should be limited whenever possible. Infections that are unrelated to skin disease, such as an upper respiratory infection, can also exacerbate atopic dermatitis. Food allergy is commonly seen in patients with atopic dermatitis but typically presents with urticaria or anaphylaxis rather than exacerbation of the atopic dermatitis.
Topical corticosteroids are the mainstay of anti-inflammatory therapy for atopic dermatitis. Hundreds oftopical corticosteroids are available and are classified according to strength from I to VII. Class I is the highest potencyand class VII is the lowest potency. Potency varies accordingto the steroid molecule (active ingredient), and, for a giveningredient, strength can vary according to relative concentration and vehicle base. Enhanced penetration occurs in areasof natural occlusion (flexures such as axillae and groin), withexternal occlusion (diapers or bandages), in areas of openskin (excoriations), and with heat or hydration. Use of wetwraps with topical corticosteroid application takes advantageof this principle of heat and hydration for enhanced penetration for recalcitrant lesions. Class I and II steroids are typically avoided in young children or in areas of thinner skin orenhanced penetration.
Corticosteroids are available in different vehicles. In general, ointments are preferred because of their increased efficacy, occlusive nature, and tolerability. Creams may be slightly less effective for a given steroid ingredient but may be more cosmetically acceptable for older patients or in warmer climates. Lotions may have more preservatives that can cause irritation and are generally less potent. Sprays, foams, solutions, and gels can be especially useful for hair-bearing areas. Creams, lotions, sprays, solutions, and gels can be particularly irritating when applied to atopic skin and should generally be avoided on areas of open skin.