SummaryBackgroundMethylisothiazolinone (MI) is used as a preservative in occupational and household products, and cosmetics. It is a part of the preparation of methylchloroisothiazolinone (MCI)/MI, which is patch tested in water in the European baseline series. However, this preparation fails to detect a significant percentage of allergic contact reactions to MI.ObjectivesTo investigate whether a separate test preparation with MI should be included in the European baseline series.MethodsLiterature survey.ResultsIn consecutively tested dermatitis patients, the contact allergy rate for MI varies between 0.6% and 6%, with a marked increase in recent years. The contact allergy rate for MI alone, not detected with MCI/MI, varies between 0% and 1.6%. Most cases are relevant, as shown by repeated open application test studies, and are mainly related to exposure from cosmetic products.ConclusionsOwing to the increase in contact allergy to MI not detected with MCI/MI, it is recommended that MI in water at 2000 ppm be included in the European baseline series. With the Finn Chamber® (diameter, 8 mm) technique, a volume of 15 µl should be applied, giving a dose of 60 µg/cm2.

Our results demonstrate that the low concentrations of formaldehyde often found in skincare products by the CA method are sufficient to worsen an existing dermatitis in formaldehyde-allergic individuals.

contact allergy to the TDM is common and inclusion into the Swedish baseline series should be considered.

Contact allergy to rubber additives in medical gloves is the most common cause of occupational allergic contact dermatitis in HCWs. Aimed patch testing with relevant rubber additives is mandatory when HE in HCWs is investigated.

Oxidized geraniol 11% pet. provides better detection than oxidized geraniol 6% pet. As most patients reacted only to oxidized geraniol, it is important to explore further whether oxidized geraniol should be included in a baseline patch test series.

In Israel, adaptation of the European directive prevails, as shown by the measurements we performed on randomly selected products.

Background: Citral is commonly used as a fragrance and flavor material and consists of the aldehydes geranial and neral. Citral is included in fragrance mix (FM) II. Geranial and neral have also been identified in autoxidation of geraniol, a fragrance compound present in FM I.Objectives: To study contact allergy to citral, geranial, and neral, and concomitant reactivity to oxidized geraniol and fragrance markers of the baseline series.Methods: A total of 1476 dermatitis patients with suspected allergic contact dermatitis were patch tested using geranial, neral, and citral, all 3.5% petrolatum (pet.) as well as geraniol 6.0% and oxidized geraniol 11% pet. in addition to the Swedish baseline series.Results: Frequencies of positive reactions to citral, geranial, and neral were 2.9%, 3.4% and 1.9%, respectively. Together, citral and geranial gave 4.2% positive patch test reactions in consecutive dermatitis patients. In patients with positive reactions to citral or its components, 25% to 34% reacted to FM II and 61% reacted to oxidized geraniol.Conclusions: Patch testing with citral, its components, or oxidized geraniol detects contact allergic reactions not detected using the baseline series. Patch testing with pure geraniol was shown to be of little value. Geranial and neral, although closely chemically related, are concluded to be separate haptens. K E Y W O R D Sallergic contact dermatitis,

Summary Background In a European study on contact allergy in the general population, it was hypothesized that the combination of contact allergy to a fragrance together with a history indicating dermatitis at exposure, and thereafter subsequent avoidance of scented products, implied a diagnosis of allergic contact dermatitis. Objectives The primary aim of this study was to validate this hypothesis and algorithm. The secondary aim was to investigate whether there was any association between the outcome of the repeated open application test (ROAT) and the patch test reactivity. Methods In total, 109 patients with and without contact allergy to fragrance mix (FM) I were recruited. Volunteers from six European dermatology clinics participated in the study including a patch test and a ROAT. Results Positive ROAT reactions were noted in 26 of the 44 volunteers with contact allergy to FM I. None of the volunteers reacted to the vehicle (P < 0·001). More individuals with a positive algorithm had positive ROATs than those with a negative algorithm. However, the difference was not statistically significant. The lower the patch test concentration eliciting a positive test reaction, the more likely a positive ROAT and the more likely that the positive ROAT appeared early during the investigative period. Conclusions The algorithm used in this study was not substantiated in this ROAT set‐up. The stronger the patch test reactivity the more likely was a positive ROAT and the more likely it was that the positive ROAT appeared early during the application period. What's already known about this topic? To the best of our knowledge, a scientifically designed and conducted repeated open application test (ROAT) has never been performed before to validate a diagnosis of allergic contact dermatitis partly based on a questionnaire. What does this study add? This is the largest controlled, randomized and blinded ROAT performed to date. Higher patch test reactivity to fragrance mix I indicated a greater likelihood of a positive ROAT. What are the clinical implications of this work? Further refinement of the questions is required in order to diagnose allergic contact dermatitis from fragrances based on a questionnaire.