My DD just got over a cold and the rest of my family wasn't sick. Well my step daughter and DH ended up getting a horrible head cold that they got from her. Breastfeeding is amazing for passing immunities but its not a fail safe. The good news is that its likely your baby's cold will be shorter in duration and not as bad.
We took DD in to the doctor because she had a fever. Doctor was not concerned at all, and she did say that DD was about to get some teeth which could be causing the cold symptoms instead of catching something. So it could be just due to teething. DD ended up getting both top teeth a week later, and one of teeth next to the top front two just poked through, so 3 teeth back to back for a total of 5 at 5 months! Girl's intense.
DD Seraphina born at home on 2/21/2012!"Childbirth is more admirable than conquest, more amazing than self-defense, and as courageous as either one."
Babies get sick. Breastfeeding isn't a guaranteed get out of viruses free card, it just makes things easier on the immune system. My exclusively breastfed babies were sick from 2 months straight through to about 8 (well, we started solids at 7, but...)
My lil one was breastfed and had congestion like you describe periodically - he didn't act sick, no fever, etc. I suppose I'll never know for certain, but I suspect most of the time it was teething related. That, or perhaps a very, very mild cold. I wouldn't worry too much, but do look out for signs that it may be getting more serious (fever, lots of green snot, green goop in the eyes, baby not acting like himself, lethargic/clingy, etc.). If it seems like it's getting worse, I'd consider getting him checked out - otherwise, it's probably fine. I can remember my lil one having that fairly often as an infant. Good luck!
eta: cold mist humidifier, saline spray (lil noses), and bulb syringe (for sucking out boogers) have been lifesavers for us! Also, as an alternative to the saline spray, just keeping baby in a bathroom with hot shower running - the steam will do the trick.
~ Lucky wife of DH and loving mama to DS (04/11) ~
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