Eczema is not the only rash.
Of course I know this, but last week I got a vivid reminder when both my kids came down with different rashes at the same time.
Shmoop had had a fever that peaked at 104F a few days before. Then, on the day before our planned trip to Lake Tahoe (naturally), he suddenly became itchy all over. Wherever he scratched, a red wheal appeared, with raised white welts. Soon he was covered head to toe in something that a cartoonist might have drawn to caricature a sick kid.
Voov, the one who has eczema, developed pinpoint dark red speckles on her arms and cheeks.
I made same-day appointments, took time off work, and drove the kids to the doctor. In the waiting room, as the kids played with toys they found there, I became aware once again that there is probably no better place than a pediatric waiting room to expose yourself to virulent pathogens.
Shmoop had the first appointment. The doctor looked him over and said that the rash was probably the result of his having a fever beforehand. Kids apparently are prone to getting rashes after fevers. Shmoop probably wasn't contagious...anymore. She prescribed Atarax (hydroxyzine HCl) as an anti-itch, and prednisolone if that didn't work. (We'd tried children's Benadryl without success.)
As I type this, I realize that I didn't check out all the side effects of Atarax. It's also used "for the short-term treatment of nervousness and tension that may occur with certain mental/mood disorders (e.g., anxiety, dementia)." It worked immediately to bring the rash down, which was great. It's also great that we got him off it asap. The idea of your kid being on a mood medication is disturbing.
Voov had the second appointment, with a different doctor. "That's hand, foot, and mouth," she announced confidently without even looking closely at the rash. As it turns out, it wasn't. Upon examining it, she said she didn't know what it was, but that Benadryl would probably work. And that kids get all kinds of rashes and this one didn't look like anything serious.
This sounded fine to me. I worry less than I should about things, to make up for my wife, Hidden B, worrying more than she should. Voov's rash did clear up, after briefly spreading to her face.
Through this experience I realized why people who see your eczema often react the way they do: avoid contact, pull their kids away from yours. They don't know what's causing the rash, or if it's contagious.
And neither do doctors. Pediatricians, especially, often have no idea why your kid is sick. And doctors in general often have no idea what is causing a skin problem for anyone, adult or child. The combination of kid & rash makes for maximum uncertainty. Eczema is not the only rash, nor the only rash of which doctors don't know the cause or cure. This is something we have to accept, difficult as it is, as the current state of medicine.