It's been a few entries since we had a 'the makeup department really sucked' story, so here's another one for good measure. Margaret Hamilton's green face paint was flammable and contributed heavily to her getting burns. We know that already. What we haven't told you is that it stopped her from eating.
The green element in the paint contained copper. Copper is extremely toxic and shouldn't be ingested by humans. Because Hamilton couldn't risk putting food in her mouth in case she also swallowed some of the makeup, she could only drink liquids on set. This problem wasn't helped by the fact that the makeup took hours to come off and didn't really completely come off at all. Apparently, much like the scarecrow, Hamilton was stuck with traces of her character for quite some time after filming wrapped.