We all know that an individuals chances of developing allergies is determined by both genetics and environmental influences. While we can control environmental conditions to a certain extent, genetics is like, well, destiny: there's really nothing you can do about it, save for gene therapy, which doesn't seem likely for the to be available for the treatment of allergies in the near future.

But how much of an influence does genetics really play? A New York Times report looks into it and concludes:

Unlike hair and eye color, they stem from the interactions of a multitude of genes, some conferring protection and others contributing to the development of allergies. As a result, people may not inherit their parents' specific allergies to ragweed or pollen, but will have an increased likelihood of developing an allergy in general, particularly when both parents have one.

One study of 344 families, for example, found that when neither parent had a history of asthma, only 6 percent of children went on to develop it. But in families where one parent had the condition, 20 percent of children had the diagnosis; in families where both parents had it, 60 percent of children had it too.

Additionally, based on studies of twins (published here and here), it appears that when one identical twin suffers from hay fever, asthma or eczema, the other twin has it in 50 to 80 percent of cases. In fraternal twins, the percentage drops to about 25 to 40 percent.