I get ibs that is set off by lactose. Found this out after lots of medical tests failed to show what was wrong. My chiropractor worked it out. Going off dairy products got me ok in a few days; now I use goat milk etc.
I am a forester and so am out and about in grass most days and yes I get hay-fever. Now I find out that all the anti-histarmines I can get (here in the UK) have lactose in them. I started to use them as in past years and all ***l let loose in my gut and the old back pain started. It was then that I noticed that the box said (in small print!) "contains lactose". The pharmacist tells me that its added as a bulker so the pills look bigger, well thanks folk!!!