My unscientific, unexpert opinion is that the increase in allergies is due to many issues:
1) the increase/overuse of antibiotics, which kills all the good bacteria in your gut, thereby lowering one's immune system, which is responsible for fighting off allergic reactions, even of a low-threat level.
2) Anything else which hurts/weakens the immune system, which makes allergic reactions more severe (and is a new phenomenon, since the 80s):
b) GMO foods
c) cell phone, wifi, computer and other EMF and radio waves
d) BPA and plastics in food/water
e) birth control and other psychotic drugs being present in drinking water, in trace levels (at least)
f) increased use of aluminum in soft drinks, beer, cooking supplies
g) gradual decrease of food nutrition quality due to mass farming methods
As far as vaccines go, I'm sure there is some correlation between the PRESERVATIVE in vaccines which causes autism. Has to be.