Allergies tend to be rarer overall with dogs fed food in its natural form
At the same time though, you could bet a reasonable sum of money that the most common allergic reaction is going to be to the thing most commonly fed. And I'm betting that is currently chicken, as it is the cheapest and most readily accessible meat type, that most people use as a base or staple of their dog's diets. Since allergies develop most commonly to things that we're exposed to on a constant and ongoing basis, it stands to reason that chicken, if overfed, is going to be the thing dogs are most frequently allergic to.
In the event that someone isn't feeding chicken often, but instead gives their dog (say) beef daily, or nearly daily, then that dog would be most at risk of developing an allergy to beef.
In answer to the second part of your question - no, my dog is fortunate enough not to suffer from any allergies at all (and the risk of him developing any is fairly low, as he is never fed the same thing constantly - rarely more than 2 meals in a row, in fact).