Allergic contact dermatitis

Essentials

  • It is often not possible to differentiate allergic contact dermatitis from other types of dermatitis on the basis of clinical presentation alone.
  • The diagnostic cornerstones are established contact allergy, clinical picture of an eczema and temporally-related exposure to the allergen in question.
  • The possibility of allergic contact dermatitis should be borne in mind where dermatitis is not resolving despite appropriate treatment.

Aetiology

  • Delayed cell-mediated allergy (skin contact allergy)
  • Usually results from a long-standing exposure.
  • The most common causative agents are nickel (picture (Nickel allergy)) as well as perfumes and preservatives used in cosmetics and hygiene products.
  • Other causative agents include chemicals found in rubber, ingredients of plastics and glues (picture (Contact allergy)), chromium and cobalt compounds as well as ingredients used in skin care products.

Symptoms

  • The rash first appears at the site of exposure but may become more widespread (pictures (3) (4)).
  • After subsequent exposure, the symptoms will redevelop within 1–2 days and will gradually resolve as the exposure ceases.

Diagnosis

Investigations

  • Patch testing is usually not indicated if the history clearly identifies the causative allergen, for example nickel.
  • The diagnostics of skin contact allergy and allergic dermatitis use epicutaneous tests (patch testing (Diagnostic tests in dermatology)), which demonstrate possible sensitisation to allergens.
  • However, a positive test result does not always prove the causal relationship with the patient’s dermatitis.
  • Testing is carried out and interpreted by a dermatologist.

Treatment

  • The definitive treatment of allergic contact dermatitis is the avoidance or removal of the allergen (personal protective equipment, changing substances or methods used at the workplace, change of employment).
  • Topical glucocorticoid creams
  • Immunosuppressive medication is used occasionally in chronic cases at the discretion of a dermatologist.
Topical treatment

  • Treatment of allergic hand dermatitis: see (Hand dermatitis).
  • Moderately potent to potent glucocorticoid creams once or twice daily until the skin has healed, for 2–6 weeks as appropriate to the severity of dermatitis. A follow-up appointment is indicated if the condition has not resolved.
  • In acute vesicular dermatitis relief can often be obtained with moist compresses (10–20 minutes twice or thrice daily).

Systemic treatment

  • In cases of severe and spreading allergic dermatitis a short course of systemic glucocorticoids may be indicated, e.g. prednisolone 20–40 mg once daily for 1–2 weeks.
  • Antimicrobials are very rarely needed in allergic dermatitis, and they do not replace topical treatment. If the rash is clearly infected (picture (Hand dermatitis in a patient with atopy)), an antimicrobial may be indicated (cephalexin 500 mg three times daily for 7–10 days).

Immediate contact dermatitis

  • Based on an immediate, IgE-mediated allergy
  • Contact urticaria and protein contact dermatitis
  • Redness, pruritus and/or urticaria develop immediately (less than 30 minutes) at the site of the allergen contact. Allergens include natural rubber (latex), cat or dog (dander or hair), root and other vegetables.
  • Clearly more rare than allergic contact dermatitis, but in its chronic state its appearance may resemble that of allergic dermatitis.

Specialist consultation

  • Particularly severe and extensive cases as well as chronic forms of the conditions
  • Patch testing and the verification of diagnosis
  • A suspicion of occupational allergic contact dermatitis or hand dermatitis

References

1. Johansen JD, Aalto-Korte K, Agner T et al. European Society of Contact Dermatitis guideline for diagnostic patch testing - recommendations on best practice. Contact Dermatitis 2015;73(4):195-221.  [PMID:26179009]

2. Fonacier L, Bernstein DI, Pacheco K et al. Contact dermatitis: a practice parameter-update 2015. J Allergy Clin Immunol Pract 2015;3(3 Suppl):S1-39.  [PMID:25965350]

3. Boonstra MB, Christoffers WA, Coenraads PJ et al. Patch test results of hand eczema patients: relation to clinical types. J Eur Acad Dermatol Venereol 2015;29(5):940-7.  [PMID:25220568]


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