While a number of allergens shows limited variation across the four regions, such as Myroxylon pereirae (5.3-6.8%), cobalt chloride (6.2-8.8%) or thiuram mix (1.7-2.4%), the differences observed with other allergens may hint on underlying differences in exposures, for example: dichromate 2.4% in the UK (west) versus 4.5-5.9% in the remaining EU regions, methylchloroisothiazolinone/methylisothiazolinone 4.1% in the South versus 2.1-2.7% in the remaining regions. Conclusions: Notwithstanding residual methodological variation (affecting at least some 'difficult' allergens) tackled by ongoing efforts for standardization, a comparative analysis as presented provides (i) a broad overview on contact allergy frequencies and (ii) interesting starting points for further, in-depth investigation.

Background. The pattern of contact sensitization to the supposedly most important allergens assembled in the baseline series differs between countries, presumably at least partly because of exposure differences. Objectives. To describe the prevalence of contact sensitization to allergens tested in consecutive patients in the years 2007 and 2008, and to discuss possible differences. Methods. Data from the 39 departments in 11 European countries comprising the European Surveillance System on Contact Allergy network (http://www.essca-dc.org) in this period have been pooled and analysed according to common standards. Results. Patch test results with the European baseline series, and country‐specific or department‐specific additions to it, obtained in 25 181 patients, showed marked international variation. Metals and fragrances are still the most frequent allergens across Europe. Some allergens tested nationally may be useful future additions to the European baseline series, for example methylisothiazolinone, whereas a few long‐term components of the European baseline series, namely primin and clioquinol, no longer warrant routine testing. Conclusions. The present analysis points to ‘excess’ prevalences of specific contact sensitization in some countries, although interpretation must be cautious if only few, and possibly specialized, centres are representing one country. A comparison as presented may help to target in‐depth research into possible causes of ‘excess’ exposure, and/or consideration of methodological issues, including modifications to the baseline series.

Preservative sensitivity in the UK was last assessed in 2000. Given the changes in preservative usage, we have re-evaluated our patch test data in order to detect any changes in the trend of sensitization. The results of patch testing using the extended British Contact Dermatitis Society Standard series were collected from 9 dermatology centres in the UK. Positive reactions to each of 10 preservative allergens were captured together with the MOAHFLA indices for each centre. In total, 6958 patients were tested during the period 2004-2005. The current data were compared with previously published data. Formaldehyde and methylchloroisothiazolinone/methyl-isothiazolinone have the highest positivity rates at 2.0% and chloroxylenol the lowest at 0.2%. Parabens mix has the highest irritancy rate. Compared with the UK data in 2000, the positivity rate of imidazolidinyl urea (0.02 < P < 0.05) has significantly increased and that of methyldibromo glutaronitrile has significantly reduced (P < 0.001).

The varying prevalences of polysensitization across Europe most likely reflect differences in patient characteristics and referral patterns between departments. Known risk factors for polysensitization are confirmed in a European dermatitis population.

Allergens used for patch testing in the hairdressing series vary between dermatology centres in the UK. The aim of our study is to ascertain the hairdressing allergens currently in use and their test results in several dermatology centres in the UK. Data were obtained from databases in 9 dermatology departments. The allergens with positive results and current/past relevance were included in a new hairdressing series based on collective experience, for wider use and further evaluation.