For The Past Few Days My Daughter And I Have

For the past few days my daughter and I have been getting pimple like bumps with a white head in the middle and there is no itching. We haven't used any new products but did go swimming in a pool but has no clorine. I started with a rash on my stomach but I was the only one and came after my sunburn I got from laying out in the sun. At a loss on what it is and why?