When someone has an allergy, they're sensitive to substances that don't affect most people, for example, pollen, mold, medications, even certain foods. In people with these kinds of allergies, respiratory discomfort and swelling of the nasal passages can result from exposure to weeds, pollen, spores, dust, or pet dander.
Airborne allergens are also the frequent culprits that trigger the symptoms of asthma.
Allergy symptoms Allergies may be seasonal in nature. Or the symptoms of an allergy may develop when someone is exposed to a particular thing, such as pet dander or mold. People can also develop a severe allergic reaction following a bug bite. For some people, this type of allergic reaction can be deadly. Anaphylaxis can also occur as a result of exposure to pet dander, certain foods, or other allergens.