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Allergic Contact Dermatitis

  1. Diagnostic Features
    The characteristic distribution of the lesions can often gives a clue to a particular allergen. Removal of the suspected allergen leads to resolution of the dermatitis. A positive patch test to a suspected offending contactant support the clinical diagnosis.
  2. Clinical Presentation
    1. Both allergic contact dermatitis and irritant contact dermatitis bear similar clinical signs. In acute cases weeping and crusting will be present, while in chronic cases scaling and fissuring are the dominant findings. Sometimes, allergic contact dermatitis differs from irritant contact dermatitis in that erythema and edema may be more prominent and pruritus more troublesome in the former.
    2. Systemically induced allergic contact dermatitis: Patients who have been sensitized to topical allergens may develop generalized eczematous inflammation if these allergens or chemically related substances are ingested. e.g. Patient with a history of nickel allergy may get a widespread flare when he takes food rich in nickel; patient sensitized to topical ethylenediamine may develop generalized inflammation following treatment with aminophylline.
    3. Airborne allergic contact dermatitis and photodermatitis have a similar distribution. Look for sparing in the upper eyelids, areas below the chin, and the Wilkinson's triangles behind the ear, areas classically spared in photodermatitis.

Table : Distribution of Allergens




Scalp and ears

Shampoo, hair dyes, topical medicaments


cosmetics, contact lens solution, metal eyelash curlers, topical medicaments


Airborne allergens, cosmetics, sunscreen, acne medications, aftershave lotion


Necklaces, airborne allergens, perfumes, aftershave lotion


Topical medicaments, sunscreens, plants, clothing, undergarments (e.g., elastic waist band, spandex bra), metal belt buckles


Deodorant, clothing


Watch and watchband


Soaps and detergents, foods, poison ivy, industrial solvents and oils, cements, metal, topical medications rubber gloves


Rubber condom, allergens transfers by hands

Anal region

Hemorrhoid preparations, antifungal preparations

Lower legs

Topical medicaments, dye in socks


Shoes, cements spilling into boots

  1. Management
    1. The first step is the identification and removal of the contactant. A Patch testing* is indicated for cases in which inflammation persists despite avoidance and appropriate topical therapy.
    2. For acute inflammation with blisters and intense erythema, cold wet compresses e.g. KMnO4 are highly effective. They should be used for 15 to 30 minutes several times a days until blistering and severe itching is controlled. Prednisolone, in dosage of around 30-40 mg a day in divided doses is used for extensive inflammation. Topical steroids for reduction of local inflammation.
  2. Common Patterns of Hand Eczema
    1. Pompholyx
      Sago – grain like
      1. Recurrent eruptions of minute, non-inflammatory, vesicles on fingers, palms and soles is characteristic. Pruritus is common, sometimes lesions can be painful or it may be asymptomatic. Scratching of vesicles leads to weeping and crusting.
      2. Management
      3. KMnO4 soaks, oral antihistamines and application of mid to high potency steroids for mild cases.
      4. A short course of oral steroid is required for severe cases.
      5. Psychological factors are important. Counselling, behavioral modification may be necessary.
    2. Keratolysis Exfoliativa
      1. This is a common chronic asymptomatic non inflammatory bilateral peeling of the palms and soles. Its cause is unknown.
      2. The eruption is most common during the summer months and often associated with sweaty palms and soles.
      3. Scaling starts simultaneously from several points on the palms or soles with 2 or 3 mm in diameter round scales that appear to have originated from ruptured vesicles; however, such vesicles are never seen.
      4. The scales continue to peel and extend peripherally, forming larger roughly circular areas that resemble ringworm, while the central area become slightly red and tender. The condition resolves in 1 to 3 weeks and requires no therapy other than lubrication.
    3. Fingertip Eczema
      1. A very dry chronic form of the palmar surface of finger tip.
      2. Usually of unknown cause, but may be the result of an allergic reaction.
      3. One or several fingers may be involved. Initially the skin is moist; gradually becomes dry, cracked and scaly.
      4. The process usually stops shortly before the distal interphalangeal joint is reached. Fingertip eczema may last for months or years and is resistant to treatment.
      5. Treatment is by avoiding irritants and frequent lubrication.
      6. Topical steroid with or without occlusion may give temporary relief. Tar is an alternative treatment.
      7. Allergy and psoriasis may have to be excluded.
    4. Ring Eczema
      An irritable patch of eczema under a ring and tends to spread to adjacent area. This affects mainly young women soon after marriage or childbirth. If the ring is transferred to the other hand, the eczema will appear at the new site. The cause is due to concentrations of detergent beneath the ring and repeated friction. Removal of the ring often brings remission.
    5. Hyperkeratotic Eczema
      Plaques of yellow-brown dense scale increase in thickness and form deep interconnecting cracks over the surface, similar to mud drying in a river bed. Occurs on the palms and occasionally soles. Hyperkeratotic eczema may result from allergy or excoriation and irritation, but in most cases the cause is not apparent. Differential diagnoses may be psoriasis and lichen simplex chronicus. They may respond to potent steroid and occlusion, but recurrence are frequent.

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