Dog Allergy Questions

We purchased a puppy for x-mas this year.  Our kids had asthma when they were small but have not had any episodes for at least 5 years.  My questions are:  If you have a dog and have some level of allergy symptoms can it make colds/virus' worse?  Do allergens build up and you have a reaction or should you see an allergic reaction within the first hour or week (i.e. my assumption is that if you are allergic to a dog you are having symptoms almost immediately and everyday).  We all are struggling with what we assume is a virus that is causing some significant sinusitis.  My son had it before we got the dog and my wife and I and daughter got it after the dog arrived.  We all take allegra for seasonal allegies.  We have all also been on a round of antibiotics with some improvement but we are going to start another round this week.  Of course we are wondering if the dog is causing any of this.  Thanks for any help.