Oleacea – Olea europaea
Olive Trees

By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter

Alabama Allergy & Asthma Center Collection Station – Birmingham, Alabama

If you have been reading my recent blogs, you are aware that I am writing a series on species of plants that are principally wind pollinated and which produce pollen grains that can act as allergens. The next few blogs will focus on a few of the genera that belong to the olive family of plants. A number of genera in this family are known to produce pollen that can act as a cause of hay fever. This blog will deal with the species Olea europaea and subsequent ones will consider ash and privet.


Oleaceae (olive family) is a family of plants native to temperate and tropical regions of the northern hemisphere. There are 25 genera and some 700 species in this family. Plants belonging to the olive family are characterized by having flowers that are 4-merous and regular, and which have two stamens, with large anthers and short filaments, and two carpels with a superior ovary. The fruit produced is a drupe or samara. The leaves are simple or compound and opposite. The best-known members of this family are olive, ash, lilac, privet, Jasminum and Forsythia. The members of this family are trees, shrubs, and climbers, some of which are important economically. The olive tree (Olea europaea) is important for the fruit it produces which is the source of olive oil. The ash tree (Fraxinus sp.) is valuable as a source of lumber, and because of the toughness of the wood is often used in the manufacture of tool handles and baseball bats. Ash is also an excellent source of firewood. The shrubs forsythia, lilac, privet, fringe tree, and jasmine are valued for use as ornamentals in gardens and landscaping. Several of the genera in this family produce pollen grains which act as allergens; a significant one being Olea europaea, the olive tree.


The olive tree is found throughout the Mediterranean region and into southern Asia. It is not native to North America but occasionally may be grown is some areas of the southern U.S. and has been grown in California for centuries. Olive trees are not present in any significant number in the Southeast and as a result the species poses no significant problem for allergy sufferers in the Southeastern U. S.


Olives are anemophilous, wind pollinated, and produces large quantities of pollen. Olive pollen grains are light and readily transported by the wind. Olive pollen can trigger asthma, hay fever, and allergic conjunctivitis in individuals exposed to it. Olive pollen contains 12 allergens, with Ole e 1 being the major allergen triggering typical allergy symptoms. The allergens in olive pollen show cross-reactivity with other members of this plant family and if you are allergic to olive pollen, then you may have allergic reactions to pollen from other genera in the family. Likewise, if you are allergic to pollen from another member of this plant family, for example, ash, then you should be aware of possible cross-reactivity with olive pollen as well as certain foods, and you should take appropriate precautions if you travel to the Mediterranean area where olive trees are commonly present.


Some pictures of an olive tree with fruits and flowers are shown below. These pictures were taken from the websites shown below each of the photos.

Olive fruits

Olive leaves
Friends of Queens Park Bushland

Olive pollen
Pollen Warn Dienst