Does Parental Spit Prevent Allergies?

Possibly:

To investigate the role of pacifier cleaning, of the University of Gothenburg in Sweden and his colleagues analyzed data they had collected for a broader study about babies' allergies. Among the questions the parents had answered was what they did when their child's pacifier fell out of his or her mouth.
"We asked them how they cleaned the pacifier — if they rinsed them in water — and of course most of them did," Hesselmar says. But a lot of the parents did something else.
"They put it in their mouth, sucked on it and then gave it back to the children," Hesselmar says. "It's a quite common way to clean pacifier."
When the researchers checked to see if there were any differences between the kids whose parents sucked their pacifiers clean and those who didn't, they found there was. Those whose parents sucked the pacifiers clean were significantly less likely to have developed eczema at 18 and 36 months and less likely to have developed asthma at 18 months, the researchers say.
"Eczema is the best disease to choose [as a marker] if you want to see if a young child is becoming allergic," Hesselmar says.
Scientists think that when parents suck their child's pacifier clean, they transfer some of the harmless bacteria in their mouths to their child, Hesselmar says. In fact, the researchers found evidence supporting that when they analyzed the saliva of the babies in the study.
"We think that these bacteria ... stimulate the immune system," Hesselmar says. And that teaches it how to do its job properly, which includes not overreacting to things like peanuts, pollen and cats, he says.

I don't think I've seen too many parents here lick off their kid's pacifier before giving it back to them, but I definitely think we've gone way too far in worrying about using antimicrobial products when most things just aren't harmful to babies and the kids are probably better off being exposed to them.  I know one thing, considering the bacteria I am exposed to on a daily basis, it's going to take something right powerful to put a hurting on me.  See, mom, living as a slob has health benefits.