Poor air quality may make allergic symptoms worse. This association is supported by toxicological studies that provide evidence for the worsening of symptoms following exposure to ground-level ozone . Ozone may also modify your immune system's sensitivity to allergens and infection.

The impact

One study in particular found a relatively strong and independent relationship between poor air quality and new episodes of runny nose (rhinitis), both in terms of initiating symptoms and in prolonging episodes.

Individuals with pre-existing respiratory and cardiovascular disease are at greatest risk of worsening allergic symptoms following exposure to poor air quality.