Allergies are an overreaction by the body. What are actually harmless substances are seen as enemies and attacked. An allergic reaction occurs. The immune system reacts to these substances, known as allergens, in the same was as it would to germs, and forms antibodies. This fil shows how exactly an allergy comes about and what reactions are triggered by it in the body. At the end of the film you will find a glossary with a summary of the contents.