Contact sensitization to benzisothiazolinone: IVDK-data of the years 2002 to 2021

BACKGROUND

Benzisothiazolinone (BIT; CAS no. 2634-33-5) is used as a biocide in various products, including water-based paints, metalworking fluids, and household products. In recent years, increasing sensitization rates have been observed in Europe.

OBJECTIVE

To describe a time trend of sensitization to BIT, analyse concomitant reactions, and identify patients with increased risk of BIT sensitization.

METHODS

Retrospective analysis of data from 26 739 patients patch tested with BIT, sodium salt, 0.1% petrolatum as part of several special test series within the Information Network of Departments of Dermatology (IVDK), 2002 to 2021.

RESULTS

Positive reactions to BIT were noted in 771 patients (2.9%). Sensitization frequency varied over time and increased in recent years, peaking at 6.5% in 2020. Painters and metalworkers handling metalworking fluids, but not cleaners, had a significantly increased risk of BIT sensitization. From our data, there is no evidence of immunological cross-reactivity between BIT and other isothiazolinones.

CONCLUSION

The increasing frequency of sensitization justifies adding BIT to the baseline series. More research on the clinical relevance of positive patch test reactions to BIT and the cause for the rising numbers of BIT sensitization is needed.

HIGHLIGHTS

Frequency of sensitization to BIT has increased in recent years. The increasing frequency of sensitization justifies adding BIT to the baseline series. Painters and metalworkers handling metalworking fluids, but not cleaners, has a significantly increased risk of BIT sensitization. We found no evidence of immunological cross-reactivity between BIT and other isothiazolinones.

Patterns of concomitant allergic reactions in patients suggest cross-sensitization between octylisothiazolinone and methylisothiazolinone

BACKGROUND

Recent animal tests have indicated cross-reactivity between methylisothiazolinone (MI), octylisothiazolinone (OIT), and benzisothiazolinone (BIT).

OBJECTIVES

To retrospectively analyse concomitant reactions to different isothiazolinones in patients in an occupational dermatology clinic during the ongoing MI contact allergy epidemic.

METHODS

We searched patch test files (January 2012 to February 2017) for patients with allergic reactions to OIT, BIT, and MI, and analysed their patch test results, occupations, exposure, and diagnoses.

RESULTS

We found 61 (9.4%) allergic reactions to MI, 19 (2.9%) reactions to OIT and 9 (1.4%) reactions to BIT in a total of 647 consecutively tested patients. Seventeen (89%) of the OIT-positive patients had concomitant reactions to MI, whereas only 3 (33%) BIT-positive patients had allergic reactions to MI. The MI reactions in OIT-positive patients were almost exclusively extreme reactions (+++). Exposure to OIT was identified in 26% of the OIT-positive patients, and 56% of the BIT-positive patients had been exposed to BIT.

CONCLUSIONS

Allergic reactions to OIT were strongly associated with extreme reactions to MI, which suggests cross-sensitization. In contrast, BIT reactions were mostly independent.