Why Allergies Occur and Associated Conditions
In people who are not allergic, the mucus in the nasal passages simply moves foreign particles to the throat, where they are swallowed or coughed out. However, something different happens in a person who is sensitive to airborne allergens (substances that can cause an allergic reaction).
In people with allergies, as soon as the allergen lands on the lining inside the nose, a chain reaction occurs that leads the mast cells in these tissues to release histamine and other chemicals. These powerful chemicals cause certain cells within some blood vessels in the nose to contract. This allows fluids to escape, causing the nasal passages to swell. The swelling leads to nasal congestion -- otherwise known as a stuffy nose. Histamine can also cause:
- Excess mucus production.
Mast cells also release other chemicals (including cytokines and leukotrienes) that contribute to allergy symptoms.
Some people with allergies develop asthma, which can be a serious condition. The symptoms of asthma include:
- Shortness of breath.
The shortness of breath is due to a narrowing of the airways in the lungs and to excess mucus production and inflammation. Asthma can be disabling and sometimes fatal. If wheezing and shortness of breath accompany allergy symptoms, it is a signal that the airways have also become involved.
Other medical conditions that might accompany symptoms of allergies include: