what is the evolutionary advantage

of allergies?

Things that develop in humans don't have to be advantageous. Remember that thing, oh, MEDICINE? We can treat ourselves. Neanderthals with cystic fibrosis would have died quickly. In the modern human, treatment is available, so the gene stays in the gene pool.

Humans do not follow Mendelian genetics.

>>11
Humans do not follow Mendelian genetics.
Non sequitur (that is, the logical fallacy).
Humans are most certainly not immune to natural selection. Modern medicine and technology may have retarded it in some areas, but to claim it's counteracted it completely is complete bullshit.