Scarlet fever is simply a "strep throat" with a rash. A fairly common specific germ causes infection of the tonsils or of the back of the throat. Children under three years of age, who get an infection from this bacterial germ, usually have a fair amount of fever, lots of discharge from the nose, may seem a bit irritable, and won't want to eat much. Older children tend to complain of a pretty severe sore throat, have swollen glands in their neck, won't want to eat much, and may have a headache or bellyache.
Strep throat tends to occur more commonly in late fall, winter, and spring, mostly because people have more close person to person contact. Once exposed, the incubation period is usually very short -- less than one week. The rash you see is usually most noticeable under the arms, in the groin, or on the chest, abdomen, or back. It has a rough sandpapery feel. Diagnosis can be made by throat culture or a quicker test (rapid strep) which is not as sensitive as a throat culture. There are some people, so-called "carriers", who have the germ in their throat. They exhibit no symptoms themselves, but may spread the germ to others.
Once we are sure your child has a "strep" infection, we treat with an antibiotic to decrease the spread and to prevent the possibility of rheumatic heart disease. A majority of times these infections resolve uneventfully after proper treatment. Most commonly, patients get better within a day or two after having had an antibiotic (penicillin, if not allergic) and the rash fades over several more days. Once a child has had 24 hours of antibiotics and is feeling better without fever, he is no longer contagious. Certainly, if your child appears particularly ill with this germ or if the illness is lasting longer than you're comfortable with, you should call your child's doctor immediately.