Do you think going barefoot builds up your immunity to getting ill?

Absolutely. I'm barefoot year-round, have been for more than eleven years. I used to be sickly, from my late teens until I was 28 I was coughing and sneezing from early fall until late spring no matter what I tried. Then I started going barefoot (just for comfort and fun, while I never bought into those myths that it's dangerous or gross, I never really thought it'd do so much to improve my health either), but ever since then it's over... I have called in sick once (for two days, and not in winter), and even a minor cough is rare. 10+ years of fighting colds all winter when I still wore footwear, 11 years of being much healthier barefoot, no other major lifestyle changes at the same time. I'm never going back to wearing shoes.