Air pollution and climate change have a significant impact on human health and well-being, and contribute to the onset and worsening of bronchial asthma, allergy and other chronic respiratory diseases. Reducing exposure to indoor environmental factors that have been shown to worsen asthma symptoms or exacerbate asthma is an important part of respiratory disease management strategies. Current evidence suggests that portable air purifiers could be a useful way of reducing exposure to pollutants, especially in children but also in adults. Air purifiers can reduce the concentration of triggers of asthma in indoor air, but the results supporting their benefits for breathing problems have not always been reproducible. This paper summarizes the effects of indoor air pollution on asthma and allergies in children and adults, and the effectiveness of air purifiers in reducing the effects of pollution.