- Allergies come from a hypersensitive reaction to substances which are ordinarily harmless to others<br> <br> <br> <br> <br> <br> <br> <br> - These substances that make you overreact these are known as allergens<br> <br> <br> <br> <br> <br> <br> <br> - There are a variety of allergens, namely pollen, pet dander, dust, house mites and a lot more<br> <br> <br> <br> <br> <br> <br> <br>