Lactose intolerance has been linked to respiratory inflammation like seasonal allergies and asthma as well as inflammatory skin conditions like eczema, psoriasis and acne, (and it's actually been known for a long time that drinking too much milk or eating too much chocolate makes your skin break out with acne). When he was younger my brother had asthma and eczema that went hand in hand but when one was bad the other wasn't as bad. My mum made that link before any such studies came to light.  Perhaps it's because he doesn't have as much lactose now that he's older, or perhaps the fact he had a bone marrow transplant in his teens (essentially giving him a new immune system, because these are all auto-immune disorders), but he doesn't have asthma or eczema as an adult.  As for me, as an adult I am lactose intolerant.  I get psoriasis on my forehead, acne, hayfever and asthma-like symptoms if I have too much lactose.  Every now and then is ok, but it definitely does make all of these things flare up.