hi kristy
how long has she had the itching and when did the rash started, if she was my daughter i would take her to the doctors.
Generally no treatment is required for Fifth's disease in children. Some acetaminophen (Tylenol) will reduce the aching and fever if she has one, and Benadryl will reduce the itching. Avoid giving Aspirin to children with a fever-could lead to Reye's syndrome. Make sure she drinks plenty of fluids and rest, because the virus will dehydrate and weaken her. Keep watch of her temperature, definitely call the doctor if fever is over 100 F
Good luck I hope she recovers soon! The course of Fifth's disease is generally 1-2 weeks.