The correct option is B An overreaction from the immune system to a foreign substance
Allergies are an overreaction from the body’s immune system to foreign substances called allergens which could be pollen, pet fur, dust, seafood like prawns etc. Allergic reactions can result in sneezing, coughing, runny nose and itching. Most of the time the reactions are bothersome, but in some cases they can be life threatening and severe. Allergies may be seasonal, such as hay fever but they may also be associated with chronic conditions such as asthma or sinusitis.