What are the Symptoms of Allergy?

Symptoms of allergy often depend on the route of exposure to the allergen.

Symptoms of allergy have a pattern. Pollen allergies appear at the same time every year. Pet allergies happen when one is around a certain animal, or in many cases, just enter a building where the animal lives. Dust allergies crop up while cleaning the house, shaking out rugs or on entering a very dusty building.

Symptoms of allergy arising from air-borne allergens like pollen, dust etc. include -

Allergic rhinitis- A cold that never seems to go away. A running nose, congestion, or coughing that occurs pretty much constantly and lasts for more than 10 days can point to allergies.
Wheezing or frequent coughing could indicate a serious allergy or asthma.
Eyes are persistently red and itchy.

Symptoms of allergy due to foods or medicines include -

Abdominal pain
Bloating
Vomiting
Diarrhea
Skin hives
Itchy skin

Rarely, allergies can set in a severe reaction called anaphylaxis, which is life-threatening. In an anaphylactic reaction, the body launches an emergency state of allergic reaction, flooding all systems with histamine and other chemicals. Capillaries and blood vessels expand (which explains the sensation of flushing and the dangerous drop in blood pressure, often described as feeling faint or going into shock), the bronchial tubes constrict (causing wheezing or difficulty in breathing) and sometimes the tissues of the throat and mouth swell, a dangerous symptom that can cause suffocation, coma and even death.