Allergic contact dermatitis triggered by castor oil-containing dressings

Castor oil (CO), predominantly composed of ricinoleic acid, is extensively employed in cosmetics and pharmaceuticals. This ubiquity necessitates a thorough investigation into its role as an allergen, particularly in cases of allergic contact dermatitis.

A 19-year-old male welder developed allergic contact dermatitis from a dressing containing CO. A clinical and chemical study, including epicutaneous testing and gas chromatography–mass spectrometry (GC–MS) analysis of CO and its derivatives, was conducted. Further details of these tests can be found in the Supplementary Material S1. As there are different CO derivatives such as acetylated, hydrogenated, or pegylated, which have previously been described as a possible cause of allergic contact dermatitis,^1-3 it was proposed to carry out an extended study with the hydrogenated and nonhydrogenated forms of CO of our environment according to Renier et al.⁴ CO contained in Linitul® (Provided by Alfasigma®), nonhydrogenated CO (Cremophor® EL), Hydrogenated CO (Cremophor® RH 60), and commercial CO (Biovène Barcelona®) were studied by GC–MS (Table 1).

In the clinical study, positive patch test reactions were noted at 48 and 72 h for Linitul® and CO (Alfasigma®), while commercial CO (Biovène Barcelona®) showed a negative reaction. Positive repeated open application tests were observed with the nonhydrogenated compound (Cremophor® EL), but not with the hydrogenated compound. Chromatograms of the four samples revealed that the commercial sample lacked fatty acids found in the Alfasigma® sample. The commercial sample had an unidentified peak at minute 9.5, absent in known compound libraries. GC–MS analysis confirmed that the commercial sample was not a dilution of other samples. Fatty acids in Linitul/Alfasigma® and Cremophor® EL were consistent with other studies.⁵ However, the Cremophor® RH 60 cream lacked the ricinoleic acid signal, likely converted to methyl 12-hydroxystearate during production, a unique compound in the hydrogenated form (Table 1 and Figure 1).

Our data indicate that ricinoleic acid is the allergen responsible for allergic contact dermatitis from CO. Both, patch tests and chromatographic analysis, consistently identified it as the primary sensitising agent. Hydrogenated CO lacks ricinoleic acid. The hydrogenation process converts ricinoleic acid into 12-hydroxystearic acid, removing the allergenic double bond. GC–MS analysis confirmed the absence of ricinoleic acid in the hydrogenated sample. Our findings show that labelled essential oil products may not contain the claimed ingredients due to adulteration or chemical changes. Chromatographic analysis revealed that the commercial sample studied lacked CO entirely. Besides, the multiplicity of synonyms employed to designate the same substance, coupled with the lack of precision in labelling, renders identification challenging.

A. Delgado-Prada: Writing—original draft; methodology; investigation; writing—review and editing. M. Valls-Mompo: Investigation; methodology; formal analysis. F. Ferriols Lisart: Methodology; investigation; formal analysis. A. Sastre Sastre: Writing—review and editing; methodology; investigation. B. Tarrasó-Castillo: Writing—review and editing; investigation; methodology. A. Morales-Rubio: Methodology; formal analysis; writing—review and editing; writing—original draft. C. Morales-Rubio: Writing—review and editing; investigation; methodology; writing—original draft.