this sounds like a case of cat haters vs. cat lovers...
I too saw that investigation about having pets in the house while the children are young and it sounds very logical.
Think of the way that you get vacinated... they inject a small amount of virus to activate your immune system.
The same could very likely be true when it comes to allergies. You get exposed to cat and dog at a young age and thereby preparing your immune system
for the rest of your life.
It should be commonly known today that a childs immunesystem is very adaptable.
On another side I also read that having pets such as cats and dogs actually can help against depression. I for one always felt a little bit,
"happier", after having petted a dog or especially a cat.
Here in Denmark they recently did studies on the front of dementia and found that pets who likes being cuddled also can help them. However it was not
thought sensible to have real live pets around people with dementia regarding caretaking and cleanlyness, so they developed some robotpets.
The ones I saw was baby seals with top of the line fur

and even sound (although the sound was awful... sounded a bit like the seal was lost from
its mother)