Are fifth disease, cold sores/herpes, and pityriasis rosea related in any way to each other?

The first two are: Caused by viruses, parvovirus b19 and herpes simplex respectively. The third is a skin disease that might be triggered by a virus but not clear.

Viruses!: If treated properly, fifth disease (parvovirus b19) goes away on its own. So does pityriasis. Cold sores/oral herpes (hsv1), however, do recur, especially with stress or a compromised immune system (have a cold or another infection). Cold sores can be reduced by certified dentist-assisted laser therapy, and/or by using topical washes or ointments like gly-oxide and viroxyn.