That's a question we've been asking ourselves quite a bit lately. After a quick googol search, I found out a lot of parents have that same question. I was more relieved to find out that this is common and to be somewhat expected. Not to say that kids getting sick should be taken lightly. There's always the chance that they could catch something serious, but with one of the kids in school (Ashie) or daycare, they are almost certain to get sick. Even more so in the winter months. If your kids only get sick in your home and they seem to get better (or not show any sick symptoms at all) when your out and about and out of your house, then you might want to look at something in the house being the trigger. Either allergens (dogs, cats or other pet or dust related allergies) or, not to freak you out or anything, even mold. If your concerned about mold or think it might be making your family sick call your doctor or pediatrician and ask them their opinion, especially if they've seen you or your kids quite a few times recently.
Here's a good website that has some mold information.
Here's another.
Now if your kids are just getting sick often, that's ok and it does get better. If one of your children are in school or daycare, they're going to be sick a lot. I say one doctor write 8-10 times a year is normal so to speak.
Here's an article that helps explain why kids are always sick. I think my kids are up to 3-4 this year. It will break during the summer months too apparently. We've got their medicine routine down pat and are quite the pharmacy frequenters. If in doubt, ask questions! They are medical professionals for a reason! I'm not to shy to call the pediatrician's office as many times a day as I need to. Sure they know us by name and face and that's always good. Your pharmacy person is a good source of quality information too. I always ask them if this is ok to take with that or is this going to make my kids go-to-bed-early tired or go-to-bed-at-2-in-the-morning overactive. They're always helpful and always overworked. Cheers to a good job medical professionals! Way to handle obsessive parents like us. Cheers to you.