@ysmina-- We all actually carry strep bacteria on our skin that can potentially cause an infection. There are hundreds of different types of strep bacteria, a few of which naturally reside on us. But if our immune system is weak or if there is a break in our skin due to a rash or an injury, the bacteria can grow out of control and cause an infection.
I also think that frequent rashes are a sign of a weak immune system or a sign that the immune system is not functioning normally. So it's not surprising for someone to experience a rash and a skin infection at the same time.