Sorry to hear you got sick, I had something similar happen.
My co-workers don't know I have celiac, and I became very sick after an accidental glutening which caused me to have diarrhea for an entire month. I became very run down and dropped to 117 pounds, which is underweight for my height. It got to the point where I could barely function and had to call in sick. It was very annoying when I showed up for work the next day and people jokingly made comments that I wasn't really sick, and even that I must have been partying the night before. This was all based on the observation that I didn't 'seem sick' to them since I didn't have a cold or seem congested. It made me wonder if my bosses were thinking the same thing.
If you live in the U.S. celiac does fall under the Americans With Disabilities Act. I've never had to bring up the topic at work with HR, but it's good to know if I became sick again.