Bay leaf

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Code: f278
Latin name: Laurus nobilis
Family: Lauraceae
Common names: Bay leaf, Sweet Bay, Sweet Laurel, Laurel leaf, True Laurel, Mediterranean Bay leaf
Two other leaves designated as “Bay” or “Laurel” are particularly important:
  • California Bay leaf, from the California Bay or Laurel tree (also known as Oregon Myrtle and Pepperwood; Umbellularia californica), is similar to the Mediterranean Bay leaf except for a stronger flavour.
  • Indian Bay leaf, from the Cinnamomum tejpata or Cinnamomum tamala tree, is similar in fragrance and taste to Cinnamon bark. In appearance, however, it is similar to the other Bay leaves.

Spice
A spice, which may result in allergy symptoms in sensitised individuals.

Allergen Exposure

The Bay or Laurel tree is generally a small, hardy, evergreen tree or shrub with inconspicuous white flowers, small blackish berries and glossy aromatic leaves that are used for flavouring in cooking. The story of Daphne and Apollo shows the ancient Greeks’ belief in the divine origin of the tree and explains their use of the leaves to crown victorious athletes. The Bay tree is indigenous to Asia Minor, from whence it spread to the rest of the Mediterranean and then to other regions with similar climates.

The Bay leaf is a hardy evergreen shrub that grows wild or cultivated. In warm areas it can grow as high as 18 m. Inconspicuous white flowers arrive in clusters, in May. The fruits are small, 12-mm, red-blue, single-seeded berries that later turn black.

The Bay leaf is oval, pointed, smooth, and 2.5 to 8 cm long. Leaves can be harvested and used at any time. When fresh, it is shiny and dark green on top with a paler underside. When dried, the Bay leaf is a dull olive green. When broken, it exudes a warm, pungent bouquet through the release of aromatic oils (which constitute about 2% of the total weight).

Bay flavours soups, stews, meats, fish, stuffings and pâtés in Mediterranean cuisine. Typically, the leaf swims, whole or slightly broken, in a cooking sauce and then is removed, either by the cook or by the diner. Bay is also used in pickling and marinating. Bay oil or Oil of Laurel is used as a flavouring, most commonly in vermouth, but also to create a spicy or savoury flavour in a variety of other processed products.

Bay oil has been rubbed on rheumatic joints for pain relief. It may be used in aromatherapy. In ancient times, the leaves were chewed for their purportedly hallucinogenic properties.

Allergen Description

No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, but in fact does not occur frequently. (1)

Cross-sensitisation has been demonstrated between 2 allergenic plants, Frullania and Laurus Nobilis. (2, 3)

Clinical Experience

IgE-mediated reactions

Anecdotal evidence suggests that Bay leaf may cause symptoms of food allergy in sensitised individuals; however, no studies have been reported to date. A number of reports have described allergic dermatitis resulting from contact with Bay leaf. (2, 4, 5, 6) Occupational asthma from inhalation of Bay leaf allergen may occur. (7)

Perioral dermatitis (4) and perioral contact eczema with eczematous stomatitis as a result of hypersensitivity to Bay leaf have been reported. (8)

The prevalence of allergy to Bay leaf could be expected to be higher in occupational settings, in particular in the food industry.

An individual with occupational asthma caused by several aromatic herbs –Thyme, Rosemary, Bay Leaf, and Garlic – has been described. The diagnosis was confirmed by several inhalation challenges. (7)

Allergic contact dermatitis from the leaf and the oil has been described. (2, 5) A 55-year-old woman presented with erythema and oedema over her knees, 3 days after the application of laurel oil to relieve joint pain. A patch test to the oil was positive. (6) Allergic contact dermatitis was reported following a massage with a mixture of olive oil and L. nobilis oil. Patch testing was 3+ positive to laurel oil and 2+ to the mixture of olive oil and laurel oil. (9)

A study examined the frequency of dermatologic allergic reactions to the Asteraceae species, using a Compositae mix; 118 of 3 851 (3.1%) individuals tested were positive. Further tests for Laurel oil were positive in 50.5% of cases. (10) Allergic contact dermatitis may be sesquiterpene-lactone-induced. (11)

Other reactions

A number of studies have indicated that Bay leaf may result in physical obstruction, including duodenal obstruction secondary to Bay leaf impaction. (12) Dried Bay leaf was described as an unusual cause of upper gastrointestinal tract haemorrhage, (13) and as an uncommon foreign body in the hypopharynx. (14)

 

Compiled by Dr Harris Steinman.

References

  1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
  2. Foussereau J, Muller JC, Benezra C. Contact allergy to Frullania and Laurus Nobilis: cross-sensitization and chemical structure of the allergens. Contact Dermatitis 1975;1(4):223-30.
  3. Asakawa Y, Benezra C, Ducombs G, Foussereau J, Muller JC, Ourisson G. Editorial: Cross-sensitization between Frullania and Laurus nobilis: The allergen laurel. Arch Dermatol 1974;110(6):957.
  4. Farkas J. Perioral dermatitis from marjoram, bay leaf and cinnamon. Contact Dermatitis 1981;7(2):121.
  5. Cheminat A, Stampf JL, Benezra C. Allergic contact dermatitis to laurel (Laurus nobilis L.): isolation and identification of haptens. Arch Dermatol Res 1984;276(3):178-81.
  6. Ozden MG, Oztas P, Oztas MO, Onder M. Allergic contact dermatitis from Laurus nobilis (laurel) oil. Contact Dermatitis 2001;45(3):178.
  7. Lemiere C, Cartier A, Lehrer SB, Malo JL. Occupational asthma caused by aromatic herbs. Allergy 1996;51(9):647-9.
  8. Jirasek L, Skach M. Perioral contact eczema with eczematous stomatitis after the use of bay leaves (Laurus nobilis L.) in food. [Czech] Cesk Dermatol 1962;37:18-21.
  9. Adisen E, Onder M. Allergic contact dermatitis from Laurus nobilis oil induced by massage. Contact Dermatitis 2007;56(6):360-1.
  10. Hausen BM. A 6-year experience with compositae mix. Am J Contact Dermat 1996;7(2):94-9.
  11. Goncalo M, Goncalo S. Allergic contact dermatitis from Dittrichia viscosa (L.) Greuter. Contact Dermatitis 1991;24(1):40-4.
  12. Tsang TK, Flais MJ, Hsin G. Duodenal obstruction secondary to bay leaf impaction. Ann Intern Med 1999;130(8):701-2.
  13. Skok P. Dried bay leaf: an unusual cause of upper gastrointestinal tract hemorrhage. Endoscopy 1998;30(3):S40-1.
  14. Awerbuck DC, Briant TD, Wax MK. Bay leaf: an uncommon foreign body of the hypopharynx. Otolaryngol Head Neck Surg 1994;110(3):338-40.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.