Privet bushes are in the Oleaceae family of plants, this family include olive, jasmine and ash trees. They are very popular in the UK, often used as privacy bushes in front and back gardens.

These plants are insect pollinated and the pollen is large in size, these are both factors which lends them to have low allergenicity and are less likely to cause allergic rhinitis.

Privet has two allergens recognised by the World Health Organisation (WHO), a profilin protein, which is a panallergen and what is known as an "Ole e 1-like protein". Ole e 1 is a glycoprotein found in the pollen of olive trees, it has high cross-reactivity with the main allergens of other plants in the Oleaceae family. Ole e 1 is the marker allergen for diagnosing these linked allergens.

Other allergens found in other studies are enolase proteins and a polygalacturonase.

The pollen season for privet trees is June to July.

An allergy to privet pollen is sometimes associated with seasonal allergic rhinitis (hayfever).

A privet pollen allergy is also linked to asthma, rhinoconjunctivitis and atopic dermatitis.

As privet pollen contains profilin proteins it can sometimes be linked to Celery Mugwort Spice Syndrome (CMS Syndrome), this is when the immune system overreacts to foods because it has already been sensitised to similary shaped pollen. The symptoms of CMS Syndrome are called oral allergy symptoms as they affect the lips, mouth and throat.

Other plants containing profilin inhalant allergens are ragweed, wormwood, birch, sunflower, mugwort, plantain, poplar and oak. Profilins are also found as food allergens in kiwi, celery, peanut, chilli, watermelon, orange, hazelnut, melon, carrot, strawberry, soya, walnut, lychee, lupin, apple, cherry, almond, peach, pear, mustard, tomato and aubergine.

Other Ole e 1 pollens include olive, pigweed, sugar beet, crocus, ash, grasses, plantain, mesquite and lilac.

Enolase proteins are found as an allergen in ragweed, plane trees, various grasses and wormwood. Enolase is a contact allergen in rubber tree plants and cockroach. Various species of fish contain beta enolase proteins. The WHO allergen database specifically mentions cod, carp, catfish, salmon and tuna, but they have been found in multiple species of fish. Enolases have also been found in chicken, snake meat, pencillin, yeast and various other moulds and fungi.

Polygalacturonase protein are pollen allergens found in cedar, plane, various grasses, olive and cypress trees. They are found as a food allergen in papaya.

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