Allergic Contact Dermatitis to Linalool Hydroperoxides: Pitfalls in the Diagnostic Process-Findings from a Repeated Open Application Test Study

Background: Increasing trends of oxidized linalool contact allergy have been reported. However, the impact of reactivity and dose in eliciting allergic contact Dermatitis caused by linalool hydroperoxides is insufficiently investigated. Objectives: To perform repeated open application tests (ROATs) using the real-world concentrations of linalool hydroperoxides in patients and control participants. Materials and Methods: Patients who previously had a positive (patients) and a negative (controls) patch test reaction to linalool hydroperoxides 1.0% in petrolatum were patch tested with a dilution series of linalool hydroperoxides preparations and asked to perform ROAT twice daily with 3 concentrations of linalool hydroperoxides creams and a negative control cream for 28 days. The creams contain 44, 140, and 440 PPM of linalool hydroperoxides, representing real-world doses reported in consumer products. Results: Of all 47 participants, 31 were linalool hydroperoxides contact allergy patients, and 16 were controls. One patient had a positive ROAT reaction in the area where cream at the highest concentration of linalool hydroperoxides was applied for 28 days. Conclusions: Repeated exposure to creams containing linalool hydroperoxides at real-life concentrations could rarely elicit an allergic reaction on intact skin after 4 weeks.

Patch Testing to Methyldibromoglutaronitrile/Phenoxyethanol: North American Contact Dermatitis Group Experience, 1994-2018

BACKGROUND

Methyldibromoglutaronitrile/phenoxyethanol (MDBGN/PE) is a broad-spectrum preservative mixture used in consumer and industrial products.

OBJECTIVES

The aims of the study were (1) to characterize the prevalence and clinical relevance of patch test reactions to MDBGN/PE and the epidemiology of positive patients and (2) to determine the frequency of concomitant reactions of MDBGN/PE and its components.

METHODS

This study used a retrospective analysis of cross-sectional data compiled by the North American Contact Dermatitis Group from 1994 to 2018.

RESULTS

Of 55,477 tested patients, 2674 (4.8%) had positive patch test reactions to MDBGN/PE (1.0%-2.5% petrolatum [pet]); most were + (63.3%) or ++ (22.3%). Clinical relevance was considered definite in 3.0% and probable in 19.3% of reactions. Common dermatitis sites included the hands (26.4%), scattered/generalized distribution (24.7%), and the face (18.3%). Patients with a positive reaction to MDBGN/PE and/or MDBGN and/or PE were significantly more likely to be male and older than 40 years and/or had hand dermatitis (P ≤ 0.0033). Positivity to MDBGN/PE 2.0% pet decreased significantly over time (from 6.0% in 1998-2000 to 2.5% in 2017-2018, P < 0.0001). Personal care products were the most common exposure source (53.2%).

CONCLUSIONS

Over time, positivity to MDBGN/PE 2.0% pet decreased significantly from 6.0% (in 1998-2000) to 2.5% (in 2017-2018). The high proportion of weak (63.3%) reactions underscore the need for careful interpretation of patch test sites. Important demographic associations included male sex and age older than 40 years.

Skincare products containing low concentrations of formaldehyde detected by the chromotropic acid method cannot be safely used in formaldehyde-allergic patients

BACKGROUND

Formaldehyde is a well-known contact sensitizer. Formaldehyde releasers are widely used preservatives in skincare products. It has been found that formaldehyde at concentrations allowed by the European Cosmetics Directive can cause allergic contact dermatitis. However, we still lack information on whether formaldehyde at low concentrations affects dermatitis in formaldehyde-allergic individuals.

OBJECTIVES

To study the effects of low concentrations of formaldehyde on irritant contact dermatitis in formaldehyde-allergic individuals.

METHODS

Fifteen formaldehyde-allergic individuals and a control group of 12 individuals without contact allergy to formaldehyde and formaldehyde releasers were included in the study. The individuals performed the repeated open application test (ROAT) during 4 weeks with four different moisturizers releasing formaldehyde in concentrations that had been determined as > 40, 20-40, 2·5-10 and 0 p.p.m. by the chromotropic acid (CA) spot test. Dimethyloldimethylhydantoin was used as a formaldehyde releaser in the moisturizers. The ROAT was performed on areas of experimentally induced sodium lauryl sulfate dermatitis. The study was double blind, controlled and randomized.

RESULTS

Nine of the 15 formaldehyde-allergic individuals had reappearance or worsening of dermatitis on the areas that were treated with moisturizers containing formaldehyde. No such reactions were observed in the control group (P < 0·001) or for the moisturizers without formaldehyde in the formaldehyde-allergic individuals (P < 0·001).

CONCLUSIONS

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.