My wife was recently canning tomatoes, and her aunt asked if she was on her period because supposedly that will ruin the batch. Her grandmother is the one that taught her aunt, but neither of us had heard anything like that.
A cursory search turned up tons of anecdotal evidence, but it's entirely possible (likely?) that it's just people trolling. For example:
Some outlandish reader-suggested myths:
“Growing up Italian, a yearly chore would be helping with canning tomato sauce.. in September. The only way to get out of it.. was to be on your period. If you were on your period, you would be excused as they believed that you would ‘SPOIL’ the sauce.”
“If you were on your period and you touched a plant, you would cause the leaf to turn brown. So no touching any plants during your period.”
— Angela Fabiano
In any case, we didn't find any kind of scientific evidence one way or the other.
Does canning (tomatoes) while on your period ruin or in some other way affect the canning process?