D'Arcy Developments

Actually D'Arcy's been with his dad, so I was spared that excitement this time. He's been trying hard to learn to read, so of course he has got sick again. It sounds weird, but every time he gets to a major milestone he has got sick, and the sick usually happens the same way - he'll start by getting cranky and then go a bit floppy. Then his temperature goes up, and up, and up. Then he throws up (a few times) and the fever goes away. Sometimes he's left with a bit of a cold, but other times it seems less than that. It all happens over a couple of days (this one started 36 hours ago) .That is how it's been with him since the first time he got sick - I mean he still gets normal colds and flus and gastros, but he also gets this developmental sick. Weird. Any thoughts on that?