Well, when I was flaring badly and got the flu it sure didn't help, lol. Other than that though, colds don't make my UC worse, and I get a flu shot every year, so I haven't gotten it again.
Whenever I'm around sick people or feel susceptible to colds/flu I start taking my vitamin c and do pretty well.
19yr old female diagnosed with UC (pancolitis) in 2005 at age 15
125mg Azathioprine 1xday / 1 Mesalamine enema every night /
2000mg Fish Oil 1xday / 500mg Turmeric 3xday /
450mg Boswellia 1xday / 400IU Vitamin E 1xday
Arthritis in both knees
Also: asthma, acid reflux, and Reynaud's Syndrome