Now, I'm not a lawyer and there have been many cases where people have been charged with something when it was only an accident but, with that being said, I should think the only way he could be charged would be if he knew that she was allergic to peanuts and kissed her anyways.
This (on the surface) seems to be an accidental death, similar to what would happen if you're playing baseball and line drive one to the head of an opposing player.
Though there have been cases involving criminal negligence causing death where you allowed a dangerous situation to continue knowing that someone could get hurt. I don't think this would apply in this case as they would have to proove he knew about the allergy.....
As for the driving analogy: if you run over someone while driving it has to be proven that you were negligent. ie: impaired in some way or that you could have avoided hitting the person. For instance: if you're driving down the road and someone chases a ball, dog, ?? into your path and you nail them, charges would most likely not be filed. However, if you were speeding on an icy road, lost control and drove your car onto the sidewalk killing someone, charges would likely be laid.
Funny thing though, you're hearing more and more about people developing allergies to all kinds on things. I wonder if this is a result of the pollutants or contaminents we are putting into our environment?