Summary

Oregano is a perennial aromatic plant frequently used as seasoning in Mediterranean countries, particularly in Turkish, Greek and Italian cooking. Food allergic reactions caused oregano are very rare, with occurrences being limited to single case reports. Symptoms of oregano allergy include pruritus, swelling of the lips and tongue and upper respiratory difficulty. Contact reactions to oregano are also possible in sensitized individuals.

Epidemiology

Worldwide distribution

Allergic reactions caused by ingestion of oregano are very rare, with occurrences being limited to single case reports.

Route Of Exposure

Main

Ingestion.

Clinical Relevance

Oregano allergy caused by ingestion has been reported in a 45-year-old male patient. He had previous history of IgE-dependent rhinitis and asthma. Within a few minutes of ingesting pizza containing oregano, the patient exhibited pruritus, swelling of the lips and tongue, dysphagia, dysphonia, progressive upper respiratory difficulty, and intense facial and palpebral edema. The symptoms abated after receiving epinephrine, corticosteroids, antihistamines and fluid therapy in an emergency care unit. Skin prick testing for was positive for oregano and thyme, as well as other members of the Lamiaceae family, reactions were negative in 10 control subjects. The patient subsequently experienced allergic reactions to food containing thyme alone. The patient had detectable specific IgE levels to oregano, thyme, marjoram and basil, the control subjects were negative.

Atopic Dermatitis

In a study of 55 patients with suspected contact dermatitis, skin patch testing with a group of spices was performed, with the most common reactions being to ginger (12.7%), nutmeg (9.1%), and oregano (7.3%).

Cross-Reactivity

Although reports are limited, cross-sensitivity between oregano and other plants of the Lamiaceae family (e.g. thyme, marjoram and basil) has been suggested.