Why is my dry skin always breaking out in tiny red spots?

I have dry skin which often flakes if I don't moisturize and has no shine to it. Everytime I use sunscreen or even just when I work out hard at the gym I break out in tiny red spots especially around my cheeks which aren't pimples. What is this caused from and what kind of makeup that isn't to heavy or won't upset my skin will counteract the redness?Why is my dry skin always breaking out in tiny red spots?
Well my sister had the same thing it is just from the heat my sister had to drink a LOT of water and wash your face alot and that worked alot for my sister now it comes back whenever she is in the sun to long!