Analysis of patch testing with cocamidopropyl betaine and its impurities in patients with intractable scalp dermatitis in a single clinic in Japan

BACKGROUND

The allergen responsible for cocamidopropyl betaine (CAPB) allergies has been debated.

OBJECTIVES

To investigate the sensitizing agents of CAPB, the patch test positivity rates of impurities were examined in Japanese patients with CAPB-related allergic contact dermatitis.

MATERIALS AND METHODS

Thirty patients with scalp dermatitis and positive patch tests for CAPB and/or lauramidopropyl betaine (LAPB) were enrolled in this study. They were patch tested with the detergents that they had been using at the time of their first visit and with the impurities dimethylaminopropylamine (DMAPA) and lauramidopropyl dimethylamine (LAPDMA).

RESULTS

The positivity rate in patch tests of the 37 detergents that the patients had been using was 78.4% (29/37). The positivity rates of DMAPA 1% pet., 1% aq. and 0.2% aq. were 32.1% (9/28), 14.3% (4/28) and 13.3% (4/30), respectively, whereas those of LAPDMA 0.1% and 0.05% were 30.0% (9/30) and 16.7% (5/30), respectively. Among the 30 patients, 6 exhibited positive results for both DMAPA and LAPDMA, 3 showed positive results for DMAPA alone and 6 produced positive results for LAPDMA alone.

CONCLUSION

Patch tests produced an overall positivity rate for DMAPA, LAPDMA or both of 50.0% (15/30) in patients with scalp dermatitis and positive patch test results for CAPB and/or LAPB.

[A CASE OF ALLERGIC CONTACT DERMATITIS CAUSED BY DETERGENTS CONTAINING COCAMIDOPROPYL BETAINE IN WHICH AN IMPURITY WAS THE POSSIBLE CAUSATIVE AGENT]

Cocamidopropyl betaine (CAPB) is an amphoteric surfactant. It has several functions, including producing effervescence and washing effects, and thus, it is used in many cleansing products, such as shampoo and liquid body cleansers. Recently, it has become clear that some impurities that arise during the manufacturing process can have sensitizing effects. Herein, we report a case of allergic contact dermatitis caused by detergents containing CAPB, in which an impurity was determined to be the possible causative agent by patch testing and chemical analysis.A 64-year-old Japanese female developed a skin rash on the hairlines of her forehead and nuchal region one month before her first visit to our clinic. Later, the rashes, which were composed of desquamative erythema, expanded to her face, neck, upper back, and chest. Patch tests produced positive results for a shampoo and liquid body cleanser (1% aq.) that she had used as well as for CAPB (1% aq.); lauramidopropyl betaine (LAPB) (1% aq.); and lauramidopropyl dimethylamine (LAPDMA) (0.05% aq.), which is an impurity of CAPB. The rashes resolved completely after we instructed her to use products without CAPB and LAPB. When issuing such instructions, clinicians should have correct knowledge about surfactants, such as the differences between cosmetic ingredient names and quasi-drug ingredient names.