For the past 5 days, I have had small bumps on my abdomen, sides, chest, neck, and back. They all appeared at once as I noticed them Tuesday night when I was about to go to sleep. I figured it was because I had worn a recently bought top that day without washing it first. Since then, I have showered 4 times but the marks are still there, everything I've worn since then has been cleaned, and they have gotten slightly redder since first appearing. They do not itch and they slightly look like pimples but without a tip where puss would come out. I'm female, 19 years old, and have never had chronic acne, a pimple here or there every few months. Ive never seen anything on my body like this and I have tried googleing multiple things but everything I find looks a lot worse than what I seem to have. As far as I know I have never been allergic to anything, I haven't traveled anywhere recently, and I live in Northern Maryland. I put some cortizone on about 20 minutes ago to see if it would do anything. I'm attaching a photo for reference. What could it be and will it go away on its own? Thank you.