Love, honey and… a runny nose? Linden allergy is no frill

“Guest, sit under my leaf, and rest! The sun will not reach you here, I promise you…”.
The promise of the famous black linden sounds so tempting that it is impossible to refuse its invitation. The tree has been entangled in symbolic and cultural contexts since time immemorial [1]. After all, it provides shade and asylum for peasants weary of field work, poets seeking inspiration and lovers whispering secrets to each other among the leaves.

Magical tree

Historically, linden trees were attributed with protective, almost magical powers. Therefore, it was eagerly planted near houses and shrines to bring blessings. Resting under a linden tree to this day is a metaphor for inner harmony. The tree spreads a mantle over us that shields, soothes, puts us to sleep and heals us. It has healing blossoms, soft, malleable wood, and an enchanting fragrance that lures honeybees… [1].

It is easy to immerse oneself in this Arcadian image. But nature, while beautiful and so readily romanticized, can also surprise us – and bring us ruthlessly down to earth. After all, can people with hypersensitivity to tree pollen also count on a moment’s respite in the shade of a linden tree and benefit from its healing effects?

The active ingredients in linden blossoms have diaphoretic, anti-inflammatory, antispasmodic, shielding, antioxidant, diuretic properties. And this is only half of the long list of actions attributed to them. Lime infusions are a well-known natural remedy for treating the common cold with a feverish condition, as well as aiding digestion [2]. Linden flowers are regarded by beekeepers as an excellent source of nectar, and the honey produced from them is highly valued [4].

About 45 species of linden have been identified worldwide. In Poland, the most common is Tilia cordata, the small-leaved linden, which can live up to 1,000 years [2,3,6]. Although it is primarily associated with traditional rural landscapes, it is also often found in urban landscapes. It is planted in parks and on street lawns because it tolerates pollution very well [3].

Insect-pollinated linden is actually not considered a cause of allergic reactions. However, its flower pollen also floats in the air and has sensitizing potential [6]. Linden pollen is a class 2 allergen, or moderately allergenic (similar to ash, poplar and oak) [6]. The pollen of this tree lasts from June to July or even August [4]. In contrast, the maximum concentration of pollen in the air occurs roughly during the last ten days of June and early July [6].

In recent years, increased pollen production of linden has been recorded, which may be a result of global warming and extreme meteorological phenomena [6].

How often does it sensitize?

In some countries, researchers have tried to estimate the percentage of children allergic to linden. They tested pediatric patients with rhinitis and asthma for this. Positive tests in the mentioned group had from 5.5% (in Turkey) to 11.4% (in Portugal) of patients [4]. Such data are lacking for Poland.

Linden allergen proteins have not yet been identified and used in allergy component diagnostics as separate molecules. However, preliminary studies indicate the existence of at least five such allergenic molecules [7]. Diagnosis of hypersensitivity to linden is primarily made by skin tests based on extracts from this plant [3].

So, an allergy to linden is a likely, though not easy, diagnosis. The matter is further complicated by the fact that other inhalant allergens (such as grasses) float in the air at the same time as linden pollen. These can mask the true cause of symptoms, which, by the way, are typical of all pollen allergies. They include:

• itching of the nose, eyes, palate, ears, throat,
• conjunctival congestion,
• sneezing,
• runny nose,
• cough [3].

Studies show that linden sometimes causes not only allergic rhinoconjunctivitis, but also allergic contact dermatitis. It appears that skin symptoms can occur even after using a cosmetic containing linden flower extract. There is a known case of a severe reaction (generalized urticaria with swelling of the lips, face and mouth and shortness of breath) after use of lime shampoo by an allergic person [4,5].

Aleksandra Lipiec 

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translation: Julia Majsiak