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Therapeutic Strategies

Allergic Contact Dermatitis/Contact Dermatitis

Timothy Berger Bruce Wintroub

Saturday, January 01, 2011

Overview

Contact dermatitis can have either an irritant or an allergic origin. Irritant reactions tend to appear less than 12 hours after exposure and are strictly limited to exposed sites. Allergic reactions are delayed (12-72 hours, except for primary sensitization, where an induction phase of 7-10 days is typical), and exhibit a tendency to spread as the delayed hypersensitivity reaction reaches sites where less antigen was deposited initially. Since the clinical manifestations result from the cutaneous inflammatory reaction caused by contact with an exogenous chemical agent, the therapeutic strategy is to eliminate the inciting agent and to suppress the inflammatory reaction. Irritant contact dermatitis is managed by keeping the skin moist and protecting it from further irritant exposure. Topical steroid therapy during the first week may be beneficial. The discussion below refers to the management of allergic contact dermatitis.

First steps

Limited areas of involvement

  1. If the lesions are bullous or weepy, treat with cool compresses, using Domeboro tablets or packets, one tablet or packet in 1 pint of tap water. A clean washcloth or towel should be used and applied wet (but not soaking wet) to the rash for 15-20 minutes twice daily.
  2. Prescribe a superpotent or high potency topical steroid preparation in a drying vehicle (eg, gel or cream but not ointment) to be applied twice daily to the rash. Note: For acute contact dermatitis on the face or intertriginous areas, milder topical steroid (eg, desonide, aclomethasone) or hydrocortisone 2.5% cream is preferable.
  3. For additional relief of pruritus, an astringent lotion, with or without additional ingredients such as menthol, camphor, and phenol in low concentration (≤1%), can be applied as frequently as needed.
  4. If pruritus is interfering with sleep, low doses of antihistamines (eg, diphenhydramine or hydroxyzine) can be prescribed.

Widespread involvement

  1. Systemic steroids: Topical steroids are only minimally effective for: widespread (>30% body surface area) acute contact dermatitis. Therefore, as disease becomes more generalized and/or involves face, genitalia, or other areas that compromise normal activity, a course of systemic steroids may be indicated. For re-exposure (as in recurrent episodes of poison ivy or poison oak), a 10- to 14-day tapering course of prednisone, beginning with 50 or 60 mg/day, is indicated. Administer each day's medication as a single morning dose taken with food or a glass of milk to reduce the likelihood of stomach upset and to avoid steroid induced insomnia. 

    For patients with primary sensitization (first episode), where the course may extend up to 4-6 weeks, oral prednisone beginning at 60-80 mg/day in a single morning dose may be used until the dermatitis is under control and obviously receding (usually 72-96 hours). Then reduce prednisone as often as every 3-4 days in 10-mg steps, being sure to treat the patient for at least 3 weeks from the onset of the eruption before discontinuing systemic steroids.

    Alternatively, a single intramuscular injection of triamcinolone acetonide 40-60 mg total, together with an additional 1 cc of betamethasone valerate, will provide a fairly rapid onset of action and prolonged action over 2-4 weeks. Note: Intramuscular steroids should be administered deeply intramuscularly in the buttocks to avoid possible atrophy of overlying subcutaneous fat.

    As a further precaution, in all patients who are candidates for systemic steroids, ascertain the presence or absence of absolute or relative contraindications to steroid therapy (e.g., brittle diabetes mellitus, active tuberculosis or other chronic bacterial or fungal infection, poorly controlled glaucoma, or psychiatric disease). In patients with HIV infection and other forms of immunosuppression, the risk benefit ratio for prednisone therapy should be determined on a case by case basis. Note: Women should be warned that these doses of systemic corticosteroids can cause short-term menstrual irregularities.

  2. Cool baths with oilated colloidal oatmeal can provide temporary relief for patients with extensive disease.
  3. Secondary bacterial infection, although uncommon, may occur, and can be hard to detect in extensive contact dermatitis. Administer oral systemic antibiotics, such as dicloxacillin or cephalexin 1 g/day to patients with obvious infections.

Subsequent steps

Search for the suspected allergen. In most cases of contact dermatitis, the cause is apparent, but some cases may require patch testing to pinpoint the culprit (eg, in shoes, clothing, and cosmetic and grooming products many potential contactants are present). Patch tests are best performed by physicians experienced in these procedures.

Pitfalls

  1. Because allergic contact dermatitis, particularly to plant lipid soluble antigens (poison oak or poison ivy) may be a 4-6 week illness, short courses of systemic steroids may result in recurrence. Be prepared to treat for the entire duration of the allergic reaction.
  2. Airborne contact dermatitis can be difficult to distinguish from photoallergy or phototoxicity. In airborne contact dermatitis the reaction is concentrated in folds of the face and neck (eyelids and neck) whereas these areas are relatively spared in photoreactions.

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