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.

Background and Objectives: Hand eczema is a chronic disease with negative impact on quality of life (QoL). In this study, QoL in hand eczema patients is assessed and related to age, sex, severity, and diagnostic subgroups.

It is suggested that this classification be used in clinical work and in clinical trials.

Terpenes are widely used fragrance compounds in fine fragrances, but also in domestic and occupational products. Terpenes oxidize easily due to autoxidation on air exposure. Previous studies have shown that limonene, linalool and caryophyllene are not allergenic themselves but readily form allergenic products on air-exposure. This study aimed to determine the frequency and characteristics of allergic reactions to selected oxidized fragrance terpenes other than limonene. In total 1511 consecutive dermatitis patients in 6 European dermatology centres were patch tested with oxidized fragrance terpenes and some oxidation fractions and compounds. Oxidized linalool and its hydroperoxide fraction were found to be common contact allergens. Of the patients tested, 1.3% showed a positive reaction to oxidized linalool and 1.1% to the hydroperoxide fraction. About 0.5% of the patients reacted to oxidized caryophyllene whereas 1 patient reacted to oxidized myrcene. Of the patients reacting to the oxidized terpenes, 58% had fragrance-related contact allergy and/or a positive history for adverse reaction to fragrances. Autoxidation of fragrance terpenes contributes greatly to fragrance allergy, which emphasizes the need of testing with compounds that patients are actually exposed to and not only with the ingredients originally applied in commercial formulations.

Allergic contact dermatitis (ACD) from isothiazolinones has frequently been described in the literature. Following an epidemic of sensitization to methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) in the 1980s, and more recently to MI, the Scientific Committee on Consumer Safety of the European Commission banned their use in leave‐on products, while restricting that in rinse‐off cosmetics. Despite a decreasing prevalence of ACD from MCI/MI and MI, cases caused by occupational exposure and non‐cosmetic isothiazolinone sources are on the rise. Moreover, sensitization to newer and lesser known isothiazolinones has been reported. This paper reviews the epidemiology of contact allergy to different isothiazolinones, clinical presentation of isothiazolinone‐induced ACD, most relevant sensitization sources and potential cross‐reactions between isothiazolinone derivatives. It also provides an update on recent legislative measures.

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The isothiazolinone derivatives, methylchloroisothiazolinone (MCI), methylisothiazolinone (MI), benzisothiazolinone (BIT), and octylisothiazolinone (OIT), owing to their strong bactericide, fungicide and algicide properties, are widely used in non-cosmetic products, such as chemical (industrial) products, household detergents, and water-based paints, and the former two derivatives are also used in cosmetic products. However, given their inherent sensitization potential (with MCI > MI > BIT > OIT), allergic contact dermatitis is frequently observed, both in consumers as well as workers in various industries. In this review, we provide an update on the use of MCI/MI and MI in cosmetics, highlighting certain aspects of MI; the use of excessive concentrations, the presence in some less familiar cosmetic products, and the association with unusual clinical manifestations. Furthermore, the use of isothiazolinones in dishwashing and washing-machine liquids, cleaning agents for dental care, and their general presence in multi-purpose household detergents, which may elicit (airborne) allergic contact dermatitis, is discussed. Finally, we provide a brief overview of the use of isothiazolinone derivatives in the paint and textile industry, and of OIT in the leather industry in particular.

The inclusion of methylisothiazolinone as a preservative in cosmetics might not represent the solution to the problem of allergic contact dermatitis from isothiazolinones, since it leads to primary sensitization.