An allergic reaction is an abnormal response to an otherwise harmless substance. These substances are known as allergens. Allergic reactions can be caused from substances that are inhaled, ingested, absorbed or injected.
Some common causes of allergic reactions can include:
Symptoms of a mild to moderate allergic reaction may include:
A severe allergic reaction can develop within seconds after coming into contact with an allergen. These types of reactions are known as Anaphylaxis.