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B inhalation of seasonal pollen grains
Asthma is a breathing disorder in which the patient experiences difficulty in breathing. This occurs due to the swelling up of the tissues surrounding the bronchioles. It also includes inflammation of the airways and their subsequent contractions which results in difficulty in breathing.
Asthma is mostly caused due to exposure to allergens. Allergens are substances such as pollen grains, dust mites, animal dander etc, that might induce allergic reactions in the person.
Increased asthma attacks in certain seasons, are related to inhalation of seasonal pollens. Pollen allergy is a hypersensitive reaction (enhanced response of immune system) which can results in asthma, nasal discharge and watery eyes etc.
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Eating preserved fruits and vegetables might lead to health problems related to digestion. In case the person is allergic to chemical preservatives that are being used, the effect would be visible upon coming in direct contact with the chemical. The symptoms might include skin rashes, itching, and other problems, but not necessarily asthma.
Vaccines are taken in order to prevent diseases/infections and administration of polio vaccine does not cause asthma.