If kids can grow out of food allergies, is it possible to grow into a food allergy? Within the last two years I have started getting sick with dairy.

Lactose intolerance. Allergies can develop with repeated exposure. Stomach upset from milk is not likely a true allergy. Genes code an enzyme that breaks down lactose, a milk sugar. As we age, the gene may express less and we don't tolerate milk as well. Some infants have the gene turned off, don't tolerate milk and need special formula. Undigested lactose can ferment by gut bacteria causing gas, bloating and pain.
Yes. Just as allergies can occur at any age, they can resolve at any age. If you are having problems with dairy, you want want to try lactaid - if you have lactose intolerance, it should help. Food allergies can present as any symptoms, but usually, it presents as nausea, upset stomach, loose stools, or blood in stools.