SummaryThe present guideline summarizes all aspects of patch testing for the diagnosis of contact allergy in patients suspected of suffering, or having been suffering, from allergic contact dermatitis or other delayed-type hypersensitivity skin and mucosal conditions. Sections with brief descriptions and discussions of different pertinent topics are followed by a highlighted short practical recommendation. Topics comprise, after an introduction with important definitions, materials, technique, modifications of epicutaneous testing, individual factors influencing the patch test outcome or necessitating special considerations, children, patients with occupational contact dermatitis and drug eruptions as special groups, patch testing of materials brought in by the patient, adverse effects of patch testing, and the final evaluation and patient counselling based on this judgement. Finally, short reference is made to aspects of (continuing) medical education and to electronic collection of data for epidemiological surveillance.

2-HEMA was the most important allergen in dentists and dental nurses, and MMA and EGDMA in dental technicians. Reactions to bis-GMA, DEGDA, TREGDA, EMA and EA were relevant in some patients.

Clinically relevant MI contact allergy remains prevalent across European countries, mainly because of exposure to rinse-off and leave-on cosmetic products.

In the logistic model, risk factors for the continuation of OHE were a long duration of hand eczema before diagnosis, respiratory atopy, skin atopy, and continuation in the same occupation. Those who ended up changing occupation due to their OHE had a better medical and economic prognosis.

We find that the classification system investigated in the present study was useful, being able to give an appropriate main diagnosis for 89% of HE patients, and for another 7% when using two main diagnoses. The fact that more than half of the patients had one or more additional diagnoses illustrates that HE is a multifactorial disease.

Nail cosmetics were responsible for the majority of ACD cases caused by acrylates, affecting nail beauticians and consumers, and therefore calling for stricter regulation and preventive measures. As HEMA detects most cases, and isolated facial lesions may be overlooked, inclusion of this allergen in the baseline series may be warranted.

Our data show that MI used alone also potentially induces contact allergy. Careful monitoring is needed to determine whether or not this antimicrobial is safe to use in cosmetics.

Allergic contact dermatitis caused by to epoxy products cannot always be diagnosed by the use of commercial test substances. Workplace products need to be tested.