Can scarlet fever cause future infertility in men? (my son is 5)?

There is no link between the two that I am aware of. Essentially, a good way to look at scarlet fever is simply as strep throat with an accompanying rash. I assume your cause for concern may be the peeling of skin in the groin region, which is a normal symptom of scarlet fever and not linked in any way to future infertility. That said, scarlet fever is a condition that should be treated with a stint on an antibiotic as the disease could become very serious (rheumatic fever) if left untreated.

As a side note, scarlet fever is most definitely not rheumatic fever - but the potential exists for rheumatic fever to develop from scarlet fever or any other streptococcal infection if left untreated. Rheumatic fever damages the valves of the heart. Source(s): Self (Physiology major, The University of Arizona)
WebMD: "Scarlet Fever." http://www.webmd.com/hw/infection/tp2120...

Complications of Scarlet Fever usually are related to the heart and kidney.
My daughter had SF when she was 7 (13 now) and she is developing just fine. It can hurt the heart and kidneys though although that is rare.

Also she got SF from never having strep before (she is homeschooled) took 6 weeks for the rashes to go away
No but i really dont know
Complications of Scarlet Fever usually are related to the heart and kidney. However, mumps can cause an inflammation of the testicles (orchitis) that could affect future fertility in men.
NO.