As many as 50 million adults and children in the U.S. have some sort of allergy:

A person with allergies has an immune system that treats ordinarily harmless proteins like plant pollen, pet dander, dust mites or peanuts as if they were dangerous invaders by producing antibodies to protect the body from harm.

Antibodies are proteins in your blood ordinarily used by your immune system to identify and fight off germs. The antibody associated with allergies is IgE, or Immunoglobulin E.

The tendency to develop allergies is often – but not always – hereditary, passed down from generation to generation. However, not everyone in a family will be allergic to the same things – and some won’t be allergic at all!

People who have allergies are also at increased risk of developing other allergic diseases such as asthma and eczema (allergic dermatitis).