Is PLA safe for people with corn allergies?

YES it is safe! PLA is a byproduct of corn starch. When food, like corn starch and corn byproducts, are heated past the heat-labile point, its chemical configuration changes.

Due to the extreme heat and numerous processing steps required to convert corn into feedstock and then to PLA, it would not contain immunologically reactive profilin and therefore there are no concerns regarding allergic reactions from PLA.