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Allergic Contact Dermatitis

Treatment

First-line treatment: Limiting exposure to potential contactants is an essential first step. Topical measures to reduce inflammation are first-line treatment for limited disease, and systemic anti-inflammatory medications may be necessary in cases of widespread skin involvement.

Limited areas of involvement

  • Treat with cool compresses, using aluminum acetate (such as Domeboro tablets or packets, one tablet or packet dissolved in 1 cup 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 b.i.d.
  • Prescribe a potent topical steroid preparation such as fluocinonide (such as Lidex) in a drying vehicle (e.g., gel) to be applied b.i.d. to the rash.
  • For acute contact dermatitis on the face or intertriginous areas, a non-fluorinated, low to medium-potency topical steroid (e.g., desonide, such as Desonate, Desowen, LoKara, Verdeso) or hydrocortisone 2.5% cream (such as Hytone) is preferable. Alternative treatments for the face are pimecrolimus 1% cream (such as Elidel) or tacrolimus 0.03 or 0.1% ointment (such as Protopic). Note that use of topical calcineurin inhibitors such as pimecrolimus or tacrolimus is an off-label use of these medications with limited evidence.
  • For additional relief of pruritus, an astringent lotion, with or without additional ingredients such as menthol, camphor, and phenol in low concentration ( l%) (e.g., Sarna), can be applied as frequently as needed.
  • For pruritus, antihistamines should be prescribed, e.g., diphenhydramine (such as Benadryl) 25-50 mg at bedtime or hydroxyzine (such as Atarax or Vistaril) 10-50 mg.
  • During the day, a non-sedating antihistamine can be administered for pruritus: loratadine (such as Claritin) 10 mg, fexofenadine (such as Allegra) 180 mg, or cetirizine (such as Zyrtec) 10 mg.

Widespread involvement

  • Systemic steroids: Topical steroids are only minimally effective for 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 10-14-day tapering course of prednisone, beginning with 1 mg/kg/day, is indicated.
  • For patients with primary sensitization, where the course may extend up to 4-6 weeks, a more extended course of systemic prednisone may be necessary.
  • Cool baths with oilated colloidal oatmeal (such as Aveeno) can provide substantial, temporary relief for patients with extensive disease.
  • Secondary bacterial infection, although uncommon, may occur, and can be hard to clinically detect in the setting of extensive contact dermatitis. If there is high suspicion for infection, administer oral systemic antibiotics, such as cephalexin 500 mg t.i.d., erythromycin or dicloxacillin 1 g/day to patients. An alternative treatment for patients without clear evidence of systemic illness is to recommend bleach baths (1/4 cup of bleach in a full tub of lukewarm water, soaking 10-15 minutes) every other day.

Subsequent therapy

Search for the suspected irritant/allergen: In many cases of contact dermatitis, the cause is apparent, but some cases may require patch testing to pinpoint the culprit (e.g., in shoes, clothing, and deodorants many potential contactants are present together). Patch tests are best performed by physicians experienced in these procedures.

Pitfalls

  • Keep a high suspicion for inadvertent ongoing exposure. For example, rhus dermatitis (contact dermatitis to urushiol in poison ivy or poison oak) may occur through ongoing exposure with contaminated clothing, shoes, or sports equipment.
  • Irritant reactions are often confused with allergic dermatitis by both patients and physicians. Yet the distinction is important because irritant reactions are concentration dependent. Therefore, certain agents that are irritants in one bodily site may be safe to use in another site (e.g., aluminum chloride may be an irritant in occluded, intertriginous areas but nonreactive when used as an astringent on the palms, soles, or back).
  • Airborne contact dermatitis can be difficult to distinguish from photoallergy or phototoxicity. An important clue is extension of the rash to the neck, submental, and/or infranasal areas (e.g., photoprotected areas).

When to refer to a dermatologist

  • When the diagnosis is not clear. The common differential diagnosis includes atopic dermatitis, asteatotic dermatitis, mite infestation, dermatophyte infection, drug eruption.
  • When the allergen or irritant cannot be identified. Patch testing is best performed in the hands of a dermatologist experienced with this procedure.
  • For counseling on allergen avoidance, especially when there is a documented occupational exposure that may impact the safety of a worker in the workplace.