Rosmarinus officinalis L. as cause of contact dermatitis

Because of the widespread use of botanicals, it has become crucial for health professionals to improve their knowledge about safety problems. Several herbal medicines contain chemicals with allergenic properties responsible for contact dermatitis. Among these, one is Rosmarinus officinalis L. (rosemary), a plant used since ancient times in folk medicine; at the present time it is used worldwide as a spice and flavouring agent, as a preservative and for medicinal and cosmetic purposes. The present article aims to revise and summarise scientific literature reporting cases of contact dermatitis caused by the use of R. officinalis as a raw material or as herbal preparations. Published case reports were researched on the following databases and search engines: PUBMED, MEDLINE, EMBASE, Google Scholar, Scopus. The used keywords were: R. officinalis and rosemary each alone or combined with the words allergy, contact dermatitis, allergic contact dermatitis, sensitisation and occupational dermatitis. The published case reports show that both rosemary extracts and raw material can be responsible for allergic contact dermatitis. Two cases related to contact dermatitis caused by cross-reactivity between rosemary and thyme were also commented. The diterpene carnosol, a chemical constituent of this plant, has been imputed as a common cause for this reaction. The incidence of contact dermatitis caused by rosemary is not common, but it could be more frequent with respect to the supposed occurrence. It seems plausible that cases of contact dermatitis caused by rosemary are more frequent with respect to the supposed occurrence, because they could be misdiagnosed. For this reason, this possibility should be carefully considered in dermatitis differential diagnosis.