I've used Johnson's baby powder (JBP) (cornstarch)my entire life --as did my mom-- and I've used it on my kids as well. I'd never had a problem with it UNTIL this past year.
I've always been a very big girl/woman so JBP has forever been a mainstay in my hygiene practices. I just had my second child in January 2018 (oldest is 12) and of course I used JBP with her first diaper change, as with each one until she was about a month old.
I changed her frequently, cleaned and dried her well, and always used JBP as I did with my oldest. But she began developing an irritation or rash where it looked as though the skin was peeling, from front to back and halfway down her thighs. I tried using different wipes, creams, ointments, soaps, and even diapers, but it would not let up. Never did I imagine it could have been the powder that caused it.
At her 1-month checkup we saw a different doctor than usual who said to stop using powder immediately (citing risk to lungs) and prescribed an antibacterial ointment for the rash. I thought both of those things to be weird/overbearing but I stopped using powder with her very next change just for the heck of it and waited on the ointment.
As soon as I stopped using the powder (using only A&D ointment instead) the rash began to clear and heal. It got better and better and healed completely after about a month. It took another month for the skin discoloration to change (she has medium complexion and the rash was white/pink).
Still, I thought maybe SHE was just sensitive to it and a couple months later I used it (a brand new bottle) on my own genital area for two days until I started getting the same irritation. It itched like crazy and the skin began peeling. I threw it away and I'll never buy it again. There are other brands out there but I've learned to live without powder completely.