A Mediterranean Tree
The olive tree is a long-lived tree that people have been cultivating and using for over 5,000 years. It provides fruit, olive oil, and wood, and is particularly widespread in the countries of the Mediterranean basin. Olive pollen is one of the most common causes of seasonal respiratory allergies in these regions, especially where olive trees grow in large numbers. Allergies to olives themselves or olive oil are much less common, although cases of food allergy following consumption and contact dermatitis have been reported [1,2,5].
Allergens in Olive Pollen
To this date, 15 allergens (Ole e 1 through Ole e 15) have been identified in olive pollen. One of the most important is Ole e 7- a molecule belonging to the group of so-called lipid-transfer proteins (LTPs). Approximately 47% of patients with olive allergy are sensitized to this specific allergen, which is associated with an increased risk of anaphylaxis. This risk is higher in regions where olives are widely cultivated [2,3].
It is believed that proteins are responsible for allergic reactions to olives. However, despite advances in research on the protein composition of olives and olive oil, not all allergens have been fully identified. To this date, only one allergen – Ole e 13 – has been confirmed in the olive fruit itself. It belongs to the family of thaumatin-like proteins (TLPs), which play a role in plant defense mechanisms [2,5].
Why is an allergy to olives rare?
Despite the widespread consumption of olives, food allergies to them are rare. This may be due to the processing methods used to prepare them for consumption. This refers in particular to treatment with sodium hydroxide (NaOH), which is used to remove the bitter component (oleuropein) and, at the same time, leads to the degradation of proteins from the TLP family, including Ole e 13. Although these proteins are generally resistant to external factors, prolonged exposure to NaOH causes them to break down and lose their allergenic potential. The absence or significant damage to these proteins in edible olives may explain why allergic reactions are uncommon [1].
When Should You Suspect an Olive Allergy? Allergy Symptoms
An olive allergy can manifest in various ways depending on the route of exposure to the allergen.
In cases of pollen hypersensitivity, respiratory symptoms predominate, such as:
- rhinitis,
- sneezing,
- itchy nose,
- conjunctivitis,
- asthma [8].
After eating olives (within a few minutes or several dozen minutes), the most common symptoms are:
- itching in the mouth (known as oral allergy syndrome),
- hives,
- swelling of the lips and eyelids,
- a severe systemic reaction – anaphylaxis (shortness of breath, dizziness, vomiting) [4,5,7,8].
Skin contact with olives or olive oil, on the other hand, can lead to reactions such as:
- contact dermatitis,
- itching,
- redness,
- contact urticaria [1,8,9,11,12].
These symptoms occur mainly in people who have direct and frequent contact with olives or olive oil, such as at work (pedicurists, massage therapists, estheticians, or pizza makers) [1,5,9,12].
Cases of allergic reactions triggered by inhaling olive particles during processing at olive oil mills have also been reported. Workers experienced symptoms such as:
- rhinitis,
- shortness of breath,
- chest tightness,
- wheezing [1,6].
Olive Allergy – Diagnosis and Treatment
The diagnosis of an olive allergy is based primarily on a thorough medical history and allergy testing.
The following diagnostic methods are used:
- spot skin tests (if an allergy to olive pollen is suspected),
- prick-to-prick skin tests using olives (if a food allergy is suspected),
- measurement of olive-specific IgE antibodies in the blood.
In some cases, a provocation test is performed, which involves administering a small amount of the product under a doctor’s supervision to assess the body’s reaction. Such a test can be conducted using olive pollen, the fruit itself, or olive oil.
Treatment primarily involves avoiding contact with the allergen, which means eliminating olives from the diet and exercising caution when consuming foods that contain them. For mild allergy symptoms, antihistamines are used [4,5,7].
Agnieszka Stańczak
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Translation: Julia Majsiak
