Red itchy rash after shower?

After I shower I break into small itchy red rashes all over my body. There are tiny red bumps in some of the spots. The spots are about the size of a quarter to the size of 3 quarters but irregularly shaped. They then fade over the course of the next hour. They only break out when I shower.

Does anyone know what this can be from and why it happens when I shower?

It happens even without soap, etc and has happened a month ago with different conditions in the shower and hygiene, etc. Tweet