Clinical Relevance

IgE-mediated reactions

Marjoram may uncommonly induce symptoms of food allergy in sensitised individuals. As little has been reported in the literature, adverse reactions to the closely related family member Oregano will be of help.

A 45-year-old man experienced 3 reactions to food: as a result of Oregano on a single occasion, and twice to Thyme. He had pruritis and swelling of the lips and tongue, dysphagia, dysphonia, and progressive upper respiratory difficulty, as well as intense facial and palpebral oedema. On 2 occasions he also had hypotension, vomiting, and nausea. Onset was within minutes after the ingestion of pizza containing the herb in the first instance, meat seasoned with Thyme in the second, and snails with Thyme in the third.

A 45-year-old female patient, with facial eczema that appeared 20 minutes after ingestion of Oregano and was exacerbated by sun exposure, was reported. A patch test was positive. Three other patients were reported to be positive to Oregano on a patch test, but their symptoms were not described.

Perioral dermatitis following ingestion of Marjoram has been reported.

Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, and in particular between Oregano and Marjoram.