My younger brothers are identical twins, one born vaginally and the other 20 min later via C-section. I've always said they'd be good data for these type of studies.
Anecdotally, they don't really have big differences regarding allergies or autoimmune disorders. Although growing up I always complained one stunk up the bathroom worse than the other.
Anecdotally, they don't really have big differences regarding allergies or autoimmune disorders. Although growing up I always complained one stunk up the bathroom worse than the other.