An allergy is an overreaction by the immune system by normally harmless subjects called allergens. Most people will suffer from at least one allergic reaction at some point in their life.
The most common allergens are pollen, dust mites, pet dander, insect venom and food. When a person encounters an allergen for the first time the immune system mistakenly believes the allergen is a threat and responds by producing anti-bodies to fight them.
These allergic reactions occur because the body produces white blood cells, which bind together to create mast cells. When the body is re-exposed to the same allergen, the mast cell releases chemicals to fight the allergen and protect the body. This results in an allergic response, which can range from uncomfortable to dangerous.
Symptoms may include red, watery and itchy eyes, a runny or stuffed nose, sneezing, sinus pressure, a sore throat, coughing, shortness of breath, chest tightening, and in severe cases, an asthma attack.
While there is no cure, there are ways to prevent or relieve allergy symptoms, such as avoiding specific allergens, taking medication, or immunotherapy.