Airborne allergens, ranging from pollen and dust to mould spores, per dander and fibres, are the most common reasons for allergies, with 1 in 10 people in Ireland allergic to these substances. If allergies are not treated, they can also lead to nasal polyps or swollen nasal turbinates. Common symptoms are: coughing; wheezing; red, swollen eyes; sore throat; frequent nosebleeds; postnasal drip; mouth ulcers; heartburn; irritability and depression.