There is a clear association between allergic rhinitis (hay fever) and asthma. The question of which comes first -- the allergic rhinitis or the asthma -- is not easily answered. Allergic rhinitis is considered a risk factor in developing asthma -- up to 78% of those with asthma also have allergic rhinitis.
Many people with asthma recall developing their asthma and nasal symptoms (sneezing, congestion, a runny nose, and itchiness in the nose) at or about the same time. Others developed their asthma either before or after the onset of their allergic rhinitis. We now know that almost all people with allergic asthma also have allergic rhinitis. Allergic asthma is the most common type of asthma.
Additionally, roughly one third of persons with allergic rhinitis will develop asthma. People with both conditions can expect to suffer more severe asthma attacks and require stronger medications to prevent their asthma symptoms. People with allergic rhinitis should be vigilant about reporting any persistent coughing or wheezing to their doctors. Sometimes allergy tests are done to isolate allergy and asthma triggers and allergy shots (immunotherapy) are given to reduce asthma symptoms. In addition, the presence of asthma can easily be determined with lung function tests.
The possible reasons why allergic rhinitis and asthma are related are that:
- The nasal and bronchial membranes are made up of almost the same type of tissue.
- The nerves of the upper airway (nasal cavity) and the lower airway (bronchial tubes) are connected. Both the upper and lower airways are exposed to the same external environment during breathing. When allergens reach the nasal cavity there is stimulation of nerve endings in the nasal cavity. This stimulation causes reflex neural signals to be sent to the tissues of both the nasal cavity and the lower airways. In the nasal cavity, these signals cause accumulation of fluid and the formation of mucus, while in the bronchial tubes they cause bronchial constriction and possibly acute asthma. This is sometimes referred to as the naso-bronchial reflex.
- Nasal congestion causes mouth breathing. During mouth breathing, air bypasses the nose. The air is not filtered for allergens and irritating particles, and it is not warmed or humidified. This non-conditioned air is more likely to cause bronchial hyper-reactivity and result in asthma symptoms.
- Mucus from the nasal cavity may drip from the back of the nose into the throat, especially during sleep. This dripping mucus triggers bronchial inflammation and causes episodes of asthma at night.
Allergic Rhinitis and Asthma
