How do you treat a heat rash on a dog?

Hi. The best solution for this would be to take the dog to a veterinary centre, here they can thoroughly examine the dogs rash and decide on what cream/antibiotics could be taken. IF it is not too serious or is not obviously causing irritation for your dog I couldn't really say as I'm no expert myself really. I just happen to be very interested in veterinary medicine and I have lived with dogs all my life. Hope I helped :)