L.,
I have no idea what your other responses might have been, but I moved to Scappoose May of 2005 and had my children, ages 4 and 5 then, in daycare and noticed that too.
In my experience (past daycare and being a former Professional Nanny and now running my own daycare), common colds and such can run rampant in daycare, no matter how much they try to control it. What I have noticed is that not all daycare providers are up front about other children in their care having any sort of minor cold and what they are soing about it in their home.
It seems colds are most common in daycare situations where they care for school age children as well as non school goers.
Some cold are noticable and some are not until they just past the spreadable stage.
Beings that I provide daycare, I know that some parents either don't care because they are not that in tune with their childrens needs are or they sometimes feel that they have no other choice but to slide their children through the daycare and hope it's not noticed, because work is more important. Then you have the parents that tell you (the daycare provider), "oh, susie has a small cold, it's nothing, I gave her something for it just before we came over" and what can you say as the daycare provider about that?
I know that in my daycare, I make it my business to know what the children's needs are and communicate as much as the parents will allow me to about their children in every facet (just the Nanny and mommy in me), while they are in my care. If I have the choice and it appears that a parent is trying to "pull a fast one" on me, when they come to pick up their child, I let them know about their childs health while in my care and remind them of my policies outlined in my contract that they the parent signed. Then, if the situation warrents and I feel that the child is too sick to return the next day, I'll let the parents know my feelings and remind them that it is not only their child that I have in my care and that I need to think of everyone's environment.
Usually, it's at this point that the parents understand. In other situations, parents are more than understanding. In your case though, I found it very interesting that you still breast feed and yet your child is still catching these colds. In my understanding, doesn't breast feeding make a child less prone to common colds? I believed that to be true. Then you mention your food allergies. You might be on to something there. I am sure that others may have responded that you might want to take this matter up with your doctor or you childs pediatrician.
I hope this helps! It's getting cold out there :)
And I hope your little one is on the mend...God Bless!