What causes allergies?

What causes allergies?

Harold Kaiser (Practicing Allergist and Clinical Professor of Medicine, University of Minnesota Medical School) gives expert video advice on: What causes allergies?; What happens in my body when I have an allergic reaction?; Are allergies becoming more common? and more...

The causes of allergies are complex. There's a genetic potential and then an exposure which are necessary. In other words, a two hit thing. If you have the potential to become allergic to ragweed and you live in California where there is no ragweed, you will not manifest allergic reactions. If you live in the Midwest and you have the potential, then your exposure to ragweed may or may not cause an allergic reaction. We don't know why some people have the potential to go on to develop allergies and others don't. But, the two necessary things in causing allergies are the genetic potential which you've inherited and the exposure. Also, repeated exposure is often necessary.