Re: Is it true that redheads can't get poison ivy?

Good question !

The active ingredient in poison ivy is an oil called urushiol. It is an 
allergen, so the first time you get exposed, there is no problem. Every 
time thereafter, it is bad because the body mounts an immune response to 
the skin where the urushiol is in contact.

There is some variation in the response of individuals to this allergen. 
This will be genetically encoded. 

I wasn't aware that the gene (s) for red hair were linked to genes which 
determine your response to allergens; but it is possible. 

In order to form a view, you would have to ask people of different hair 
colour (red, blond, black, brown), and get enough of a sample size to 
have a meaningful response. 

You may have something !
cheers
david