Hay fever may sound like a pastoral malady, but city-dwellers can also be hit hard by pollen allergies. Now researchers have revealed a possible factor, finding that birch trees growing in heavily polluted urban areas have higher levels of a key allergen in their pollen.
Birch tree pollen is one of the most potent allergens. About 25% of people with hay fever affected by allergy to it, according to Allergy UK.
