Lots of Vit D deficiencies out there now - especially among children. I am sure the use of sun screen will figure into this - so many parents won’t let a drop of sun touch their kids. I never used the stuff on mine.
I break out if I get too much exposure. Been on D for several months.
Some people have a fast reaction to the suns rays. I can burn in less than 15 minutes. So I use a sunscreen but very low range to filter the rays to an acceptable level.