I think the only form of medication I have ever taken apart from jabs for TB/MMR has been paracetamol (acetaminophen to you Americans) and even that's rare. And guess what, I hardly ever get ill... from memory I recall maybe 5 instances of sickness (in about 20 years, I don't remember much at all when I was 3 or 4), and I am pretty sure two were food poisoning, the others probably some form of flu bug... then maybe half a dozen common colds, though I usually get over them quickly.
Oh, speaking of allergies, I do have hayfever... but it has been getting progressively milder as I get older. (to add to my list of medications, I have tried some different solutions to hayfever but none of those meant to combat the source have worked, and it's been 5-6 years since I bothered with anything at all and I have still been getting fewer symptoms and lessened extremes, when I was 5 my eyes once puffed up to the extent that I could only see, barely, out of one eye... now I get mildy itchy eyes and nose for a couple of weeks.)