How is strep throat strep throat different from scarlet fever?

In some people...: ...Strep throat causes a rash in addition to other symptoms. It is then called scarlet fever. Except for the rash, it is the same disease.

Rash: Some strains of streptococcus cause some people to break out in a rash due to specific toxins that the strain releases in the body. It is otherwise the same with no increased risk of serious complications or problems. In order tp prevent these complications, antibiotics are needed. See your doctor

The germ: Some group A strep germs carry an extra piece of genetic code that triggers a toxin that can cause the rash. If someone has a strep infection in their throat it usually shows up within 12 hrs of the first fever. If the infection is treated very early, it may not show up at all. A strep germ without the extra gene will not trigger the rash. Scarlet fever is an old term used back before penicillin.