Allergic contact dermatitis

Authors


  • Section Editor Prof. Dr. Jan C. Simon, Leipzig

  • Conflicts of interest None.

  • Epidemiological studies currently provide no evidence for a significant change in prevalence and incidence of allergic contact dermatitis.

  • Regressions in the diagnostic depth of contact allergy favor recurrences of the disease.

  • Contact sensitizations towards not sufficiently avoidable occupational substances are next to variants of atopic dermatitis the most frequent causes of occupational disability.

  • Irritant dermatitis and the various forms of atopic dermatitis are the most important differential diagnoses of allergic contact dermatitis.

  • The possible causes of allergic contact dermatitis are as diverse as the exposures, but can be usually be identified by utilizing the available test allergens selected on the basis of history.

  • Due to the special environmental factors of stasis dermatitis, sensitizations can develop towards weak allergens that are otherwise only rarely observed.

  • True allergic reactions of the oral mucosa towards dental materials are very rare.

  • The sensitivity and specificity of the patch test are in part critically impacted by comorbidities and medications, the skin status in the test area and deviations from the defined test conditions.

  • The allergens of the standard series are of particular importance and are supplemented by special test series on the basis of history.

  • The reading of a reaction ideally is done only according to morphological criteria and at first disregards the question of the clinical relevance. Unfortunately, when at least a “+”-reaction is observed, it is often automatically assumed that a contact sensitization exists and sometimes it is concluded without further critical evaluation that this is also relevant for the disease process.

  • From large data bases by means of calculations problem allergens can be identified, whose relevance must be evaluated particularly critically.

  • An online reading training of the German Contact Dermatitis Research Group (DKG) is available for quality assurance and further education.

  • An abnormal irritant control underscores the need for careful interpretation of other weak positive erythema reactions, that can hide false-positive reactions.

  • Contact sensitizations towards sodium lauryl sulfate do not occur; the substance is a pure irritant.

  • In the strip patch test a disturbance of the barrier function is simulated in order to test allergens with poor penetration capabilities.

  • A ROAT can be very helpful to evaluate mixtures, such as cosmetics and contact substances at the workplace, for existing sensitizations towards one of the ingredients.

  • In vitro diagnostics with the lymphocyte transformation test (LTT) hardly has a place in the clinical management.

  • Histologically, the various causes of an eczema cannot be differentiated sufficiently.

  • For the differentiation from a fungal infection and an atopic dermatitis appropriate diagnostics may be necessary.

  • The exclusive testing of the standard series is not sufficient in many cases.

  • Occupationally-related diagnostics, when an occupational contact dermatitis is suspected, as well as the testing of occupational contact substances is reimbursed much more favorably within the context of the medical fee schedule of the statutory occupational accident insurance (UV-GOÄ) since 2010.

  • The present downward trend in the extent and availability of patch testing delays the diagnosis and prolongs the treatment-requiring duration of an allergic contact dermatitis.

  • Allergologic test substances are drugs and therefore are regulated with respect to manufacturing and licensing by the German Drug Law (AMG).

  • Due to the stipulations of the AMG, since 2008 no new contact allergens have been licensed for testing.

  • The testing of patients' own substances will become more important in order to close gaps in the diagnostic spectrum.

  • Diagnostics with patientsí own substances requires consideration of additional quality criteria.

  • Since the 15th reform of the AMG testing of patients' own substances requires reporting to the responsible state authority.

  • As the test result presents the sum of all sensitizations acquired in the past, even strong reactions must always be critically analyzed for their actual relevance for the current disease.

  • Even reactions whose developments are puzzling should be brought to the attention of the patient. This succeeds by handing out an allergy ID card in which the listing of the allergens with the INCI terminology mandated for the declaration of ingredients is documented.

  • Topical corticosteroids are still the mainstay in the therapy of allergic contact dermatitis.

  • An important prerequisite for therapy success is allergen avoidance.

  • Short-term pulse therapy with systemic corticosteroids helps to bring extensive contact dermatitis rapidly under control.

  • Alitretinoin cannot be recommended for the therapy of allergic contact dermatitis.

  • An effective protocol for hyposensitization of allergic contact dermatitis is still not available.

Correspondence to

Priv.-Doz. Dr. Detlef Becker

Department of Dermatology

University Medicine Mainz

Langenbeckstraße 1

55131 Mainz, Germany

E-mail: detlef.becker@unimedizin-mainz.de

Summary

Allergic contact dermatitis is a frequent inflammatory skin disease. The suspected diagnosis is based on clinical symptoms, a plausible contact to allergens and a suitable history of dermatitis. Differential diagnoses should be considered only after careful exclusion of any causal contact sensitization. Hence, careful diagnosis by patch testing is of great importance. Modifications of the standardized test procedure are the strip patch test and the repeated open application test. The interpretation of the SLS (sodium lauryl sulfate) patch test as well as testing with the patients' own products and working materials are potential sources of error. Accurate patch test reading is affected in particular by the experience and individual factors of the examiner. Therefore, a high degree of standardization and continuous quality control is necessary and may be supported by use of an online patch test reading course made available by the German Contact Dermatitis Research Group. A critical relevance assessment of allergic patch test reactions helps to avoid relapses and the consideration of differential diagnoses. Any allergic test reaction should be documented in an allergy ID card including the INCI name, if appropriate. The diagnostics of allergic contact dermatitis is endangered by a seriously reduced financing of patch testing by the German statutory health insurances. Restrictive regulations by the German Drug Law block the approval of new contact allergens for routine patch testing. Beside the consistent avoidance of allergen contact, temporary use of systemic and topical corticosteroids is the therapy of first choice.

Ancillary