# Two Cases of Allergic Contact Dermatitis Caused by Coco Betaine in Clobetasol Propionate Shampoo

## TL;DR

Two patients developed allergic reactions from a shampoo containing clobetasol propionate due to an unexpected ingredient, coco betaine.

## Contribution

Identifies coco betaine as a potential allergen in CP shampoo despite its low allergenic reputation.

## Key findings

- Patch testing confirmed allergic reactions to coco betaine in two patients.
- The active ingredient, clobetasol propionate, was not the cause of the dermatitis.
- Allergic reactions to unexpected ingredients should be considered in persistent dermatitis cases.

## Abstract

We present two cases of allergic contact dermatitis caused by the amphoteric surfactant coco betaine, a constituent of clobetasol propionate (CP) shampoo, despite the low allergenic potential of CP shampoo formulations. The patients were Japanese males, aged 49 and 52 years, with severe atopic dermatitis, who had been treated with oral cyclosporine for several years. Patch testing revealed that only coco betaine 1% aq. showed a clearly positive reaction in both cases, whereas the patch test results of CP shampoo, cocamidopropyl betaine, and lauramidopropyl betaine were positive in one case and doubtful in the other. In cases of recalcitrant scalp dermatitis, it is necessary to consider the possibility that it is being caused by the topical medication used to treat it, and that the “active” ingredient may not be the culprit.