After talking with my mom (she's very wise and frequently self diagnoses using webmd, lol) it dawned on me that Meg switched prenatal vitamins right around the time her hives started.
Originally, Meg was taking organic prenatal vitamins from Whole Foods, but when her morning sickness intensified it became too difficult for her to swallow the pills (they are quite large). In lieu of a gag reflex, we switched to chewable (gummy) prenatals from Target.
Over the weekend Meg and I went to Whole Foods in search of new vitamins. They don't make chewable prenatals, but they do make petite versions of her original vitamins.
The downside is that you have to take three of them (but they're only slightly larger than a tylenol, so it's not that bad).
Anyhow, Meg managed to swallow the new pills last night. Afterwards she took an oatmeal bath and then we covered her hives with calamine lotion (she looked like the pink panther!!!). We had to reapply in some areas before bed, but for the most part, she was comfortable.
Meg woke me up at 1:30 to reapply and then fell back to sleep. She took a shower to rinse off the lotion and then reapplied a new coat. Last I heard, she did well today.
It's still too early to tell whether my theory is correct or not, but I figured I should clue you in regardless...fingers crossed!