I don't feel guilty about it at all, but I absolutely hate to do it. At times I will have pressure from parents if I am sick and I try to avoid that pressure at all costs. Also I remember having a boss to answer to and don't want them to have to go through that.
I work if I am sick with a cold or something. If I am puking or have the runs I won't work as it is not safe to leave six children alone while I am in the bathroom.
Taking care of myself is a top priority to me. No one is going to do it for me or guilt me into not doing it.