About half the patients we see also have a herald patch. This spot, also on the torso, is typically 2 or 3 inches across and can be mistaken for ringworm. Most textbooks say the cause is unknown, it lasts 6 to 8 weeks, and there's nothing that can be done to shorten the duration. We beg to differ.

 

According to DermNet New Zealand, however, "pityriasis rosea is associated with reactivation of herpes viruses 6 and 7, which cause the primary rash roseola in infants. Influenza viruses and vaccines have triggered pityriasis rosea in some cases."

In other words, just as shingles is a reactivation of varicella (also called human herpes virus 3) in a limited area of the body, pityriasis is a flare of the human herpes viruses that cause roseola in babies.

 

Other sources such as eMedicine dispute this link but it makes sense to us. Pityriasis is not contagious. It's often preceded by a viral illness. Kids only get it once. Acyclovir, an antibiotic used to treat herpes virus, has been shown to help in bad cases.

In our practice, we once saw a teen with a wicked case of pityriasis whose mother fed her a ton of carrots and had her lay in the sun. The rash resolved in a couple days (she did look a bit orange)!  While dermatologists typically advocate steroid creams, we favor aloe or calendula topically.   

 

Other skin conditions that might be mistaken for pityriasis include nummular eczema, tinea versicolor, and PLEVA. If you're not 100% sure about your teen's rash, a visit would be prudent.