f269 Basil

Basil, a member of the mint family, is one of the oldest herbs from the Orient. It originated in India and is now found in more than 100 varieties and grown almost worldwide. It is used, fresh or dried or as an extract, to add a distinct aroma and flavour to food.

Basil is grown near almost all Indian temples and dwellings for its spiritual symbolism. In Italy, a pot of basil in a woman's window is said to be an invitation to her lover to visit her.

Basil is used in tomato pastes, soups, stews and vegetable dishes, especially in the Italian and Indian cuisines. Basil is present in chartreuse and other liqueurs. It has been used as a digestive aid and as a mild sedative.

IgE-mediated reactions

Anecdotal evidence suggests that basil may induce symptoms of food allergy in sensitised individuals (1,2); however, few studies have been reported to date. It is possible that the allergy occurs more frequently than has been reported.

Two individuals allergic to Basil were reported. A 65-year-old woman experienced an episode of dyspnoea, urticaria and angioedema involving the face and lips, which occurred within 30 minutes after eating homemade pesto Genovese sauce containing raw basil, pine nuts, garlic, olive oil, and parmesan cheese. She had previously also experienced oral pruritus each time she tasted oregano in a salad, and gave a history of sudden onset of sneezing, nasal congestion, coughing and wheezing every time she smelled lavender. The second patient, a 25-year-old male, reported the onset of oral pruritus, rhinorrhoea, nasal congestion, pruritus of the eye, lower lip angioedema, and emesis occurring 15 minutes after eating pesto sauce made with the same recipe as described above. The first patient had positive skin-prick tests to Artemisia vulgaris and to all Labiatae tested, whereas the second patient was positive to Gramineae species, basil, oregano, lavender, pistachio, cashew nut, hazelnut, almond, walnut and celery. Specific serum IgE to basil, marjoram, and thyme were negative in both patients. (1,2)

There are no or very few cases described in the medical literature of systemic allergic reactions to herbs of the Lamiaceae family, e.g. basil, oregano or thyme. In a study reporting systemic allergic reactions caused by oregano and thyme (members of the same family as Basil) in the same patient, clinical history and in vitro and in vivo results suggested cross-reactivity between these herbs and basil. Skin-specific IgE tests with plants of the Lamiaceae family, including basil, were all positive when the skin-prick technique was used; tests were negative with basil and lavender, and positive with all the others when the prick-by-prick technique was used. Serum-specific IgE was detected to all herbs tested. (3)

The presence of serum-specific IgE to basil, thyme and oregano has been reported in patients sensitised to birch pollen and celery, but these studies were based on in vitro tests and not on clinical grounds. (4-6)

In a series of 55 patients with suspected contact dermatitis, positive patch tests were most common with ginger (7), nutmeg (5), and oregano (4). Basil and clove were at zero for reactivity. (7)

Other reactions

The extract of Basil can be a skin irritant, and moderately toxic by ingestion

No allergens from this plant have yet been characterised.

Cross Reactivity

Extensive cross-reactivity between the different individual species of the genus could be expected, but in fact cross-reactivity does not occur frequently. (8)

Plants belonging to the Lamiaceae family (hyssop, basil, marjoram, mint, sage, lavender, etc.) seem to show cross-reactivity on the basis of clinical history and in vitro and in vivo test results. (3).

Last reviewed : June 2022