Further Reading

Olive tree t9

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Code: f342
Latin name: Olea europaea
Source material: Fresh fruit (black)
Family: Oleaceae
Common names: Olive

See also Olive tree t9 for allergy to olive tree pollen.


A food, which may result in allergy symptoms in sensitised individuals.

Allergen Exposure

Olive is a small, large-pitted, firm fruit of the evergreen Oleo Europaea, probably the first tree to be cultivated by man. Oil from the fruit had been produced by 3000 BC.

All olives need to be processed, and this involves removing the bitterness, since fresh from the tree they are completely unpalatable. Methods abound, creating a large variety of olive products. Processing also enhances the keeping qualities. If processed correctly, the brine should have a balance of salt and acid that preserves the fruit for years if the container is unopened and left at room temperature. (A white film may develop on the surface of the brine, but it is harmless.)

There are plenty of olive types, including Manzanilla, Gordal Sevillana, Uova di Piccione, Ascolano Tenera, Mission, Kalamata and SA Leccinouse.

Olives are very versatile. They are eaten as snacks and in dishes, baked in bread, used in salads and on pizza, and so on. Olive oil has been a staple of the Mediterranean diet since ancient times, and is still a very common ingredient in several Mediterranean cuisines. It is used both as a cooking oil and as a flavourant.

Allergen Description

Although 9 allergens have been characterised in olive tree pollen, no allergens from the fruit of this plant have yet been characterised.

The following allergen has been characterised:

Ole e 13, a 23 kDa protein, a thaumatin-like protein. (1, 2, 3)

Potential Cross-Reactivity

Extensive cross-reactivity between the different individual species of the genus could be expected, but in fact does not occur frequently. (4)

Clinical Experience

a. IgE-mediated reactions

Although olive pollen may commonly induce symptoms of allergy (hayfever and asthma) in sensitised individuals (see olive tree t9), the olive fruit only uncommonly induces symptoms of food allergy in sensitised individuals. (5, 6)

IgE-mediated food allergy following ingestion of Olive was described in a 19-year-old woman who had a 4-year history of episodes of facial, neck, and hand angioedema, and intense itch of the palms. In one of the episodes, the angioedema affected the tongue as well, and the itch was generalised. Symptoms abated in 24 hours. On each occasion, the patient had ingested olive 15 to 30 minutes beforehand. The onset of symptoms was not related to exercise. The patient tolerated olive oil and did not experience rhinitis or asthma during the pollen season. Prick-by-prick tests with 3 different types of olive were positive. Specific IgE to olive was 1.7 kU/l, and 0.73 kU/l for olive tree pollen. (3)

Contact urticaria to olive was described in a 22-year-old woman who presented with a 2.5-year history of hand dermatitis, which had started while she was working as a pizza chef. She gave a further history of perioral itching and lip swelling after consuming olive, with the severity dependent on the type of olive (which was, however, undetermined). Skin-prick test with olive resulted in a flare, but no wheal reaction. The authors suggested that while a flare reaction is not normally considered positive, in view of the definite history and the weak positive control, the reaction was considered relevant. The patient declined repeat testing with a variety of other olive types. (7)

Olive oil, produced from olive fruit, has been more frequently reported to result in adverse effects in sensitised individuals than has olive fruit.

An early study reported that 13 cases of contact allergy to olive oil were documented, but that known components of olive oil could not be proven to be the cause of the allergy. (8)

Other reports have contained similar findings: Olive oil can be a non-allergic skin irritant, but in 1 patient, the reaction could be classified as probably allergic. Among 77 female and 23 male eczema patients prospectively patch-tested with freshly-prepared olive oil, in only 1 patient could the reaction be classified as probably allergic. (9)

Jung reports on a 43-year-old female who developed increasing eczematous reactions to olive oil. She developed these reactions after treatment of her leg with a boric acid/zinc oxide preparation in an oil vehicle. (10)

Twenty cases of contact allergy to Olive oil were described, and 3 of these involved occupational hand eczema as a result of exposure to olive oil. Researchers describe a masseur who was allergic to olive oil, resulting in occupational hand eczema. Patch tests were positive. The oral provocation test was negative. (11)

Airway disease has been described in an olive oil mill worker. A 41-year-old Spanish man working in an olive oil mill reported a 2-year history of episodic rhinitis, shortness of breath, chest tightness, and wheezing. Symptoms occurred within 30 minutes after he arrived at the workplace, and partially improved immediately after he left it. A skin-prick test with olive pulp extract was positive. The patient's serum demonstrated reactivity against a 23 kDa protein band in olive fruit protein extract, and the band showed homology to allergenic thaumatin-like proteins (TLPs) from plant foods and pollen. A nasal challenge test with purified TLP was positive, with nasal obstruction, sneezing, and runny nose. (1)

Other compounds present or forming in olive oil may be responsible for the allergy-like reactions reported. Olive oil may contain lipid peroxidases, which can be inducers of irritant skin reactions. This is because unsaturated lipids in olive oil are susceptible to oxidation by oxygen in the air. Furthermore, olive oil may be contaminated with benzene or benzene derivatives such as toluene and C2 benzenes. (12) Pesticides may be present, depending on the harvest time. Polychlorinated dibenzo-p-dioxins, as residues in olive oil, can cause a variety of skin disorders. (13)

See also Olive tree t9 for allergy to olive tree pollen.

Compiled by Dr Harris Steinman, harris@allergyadvisor.com


  1. Palomares O, Alcantara M, Quiralte J, Villalba M, Garzon F, Rodriguez R. Airway disease and thaumatin-like protein in an olive-oil mill worker. N Engl J Med 2008;358(12):1306-8.
  2. Palacín A, Rivas LA, Gómez-Casado C, Aguirre J, Tordesillas L, Bartra J, Blanco C, Carrillo T, Cuesta-Herranz J, Bonny JA, Flores E, García-Alvarez-Eire MG, García-Nuñez I, Fernández FJ, Gamboa P, Muñoz R, et al. The involvement of thaumatin-like proteins in plant food cross-reactivity: a multicenter study using a specific protein microarray. PLoS One 2012;7(9):e44088.
  3. Esteve C, D'Amato A, Marina ML, García MC, Citterio A, Righetti PG. Identification of olive (Olea europaea) seed and pulp proteins by nLC-MS/MS via combinatorial peptide ligand libraries. J Proteomics 2012 Apr 18;75(8):2396-403.
  4. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
  5. Azofra J. Olive allergy. Allergy 2004;59(5):559.
  6. Zuidmeer L, Goldhahn K, Rona RJ, Gislason D, Madsen C, Summers C, Sodergren E, Dahlstrom J, Lindner T, Sigurdardottir ST, McBride D, Keil T. The prevalence of plant food allergies: a systematic review. J Allergy Clin Immunol 2008;121(5):1210-8.
  7. Williams J, Roberts H, Tate B. Contact urticaria to olives. Contact Dermatitis 2007;56(1):52-3.
  8. Malmkvist Padoan S, Pettersson A, Svensson A. Olive oil as a cause of contact allergy in patients with venous eczema, and occupationally. Contact Dermatitis 1990;23(2):73-6.
  9. Kranke B, Komericki P, Aberer W. Olive oil--contact sensitizer or irritant? Contact Dermatitis. 1997;36(1):5-10.
  10. Jung HD, Holzegel K. Contact allergy to olive oil. [German] Derm Beruf Umwelt. 1987;35(4):131-3.
  11. Isaksson M, Bruze M. Occupational allergic contact dermatitis from olive oil in a masseur. J Am Acad Dermatol. 1999;41(2 Pt 2):312-5.
  12. Biedermann M, Grob K, Morchio G. On the origin of benzene, toulene, ethylbenzene, and the zylenes in virgin olive oil: further results. Z Lebensm Unters Forsch 1996;203:224.
  13. Rodriguez-Pichardo A, Camacho F, Rappe C, Hannsom M, Smith AG, Greig JB. Chloracme caused by ingestion of olive oil contaminated with PCDDs and PCDFs. Hum Exp Toxicology 1991;10:311-22.


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