Pityriasis Rosea: What causes it?

509px-Pityriasisrosa.pngIn high school, I had a friend who developed a strange rash on his stomach and back. The rash was little red bumps that stayed on his trunk and spread slightly to his arms, but nowhere else. He wasn't allergic to any foods and hadn't changed soaps  or detergents before developing this rash. Baffled, he went to the doctor, who looked at his rash and immediately diagnosed him with what the medical community calls  pityriasis rosea.

As the article says, this is a rash that is not terribly uncommon in young people, and poses no threat. When my friend found out this was what he had, obviously those of us who were in contact with him wondered how he got it and if we could also get it. His answer, the no one knows for sure what causes this rash, raised the question I am now posing: What really causes pityriasis rosea?

There is much disagreement in the medical community when it comes to pinpointing what causes this rash. As this particular article states, some believe that it is caused by a virus. However, others completely believe that a virus is not the cause. And still, others do not rule the possibility of a virus out, linking it to the HHV6 virus. Given all of this evidence, I believe that a virus is the most probable cause of this rash, however there is room for skepticism. Before contracting the rash, many patients show symptoms of a common cold, which we know is caused by a virus. Here, there are two possibilities: 1) the HHV6 virus is causing the cold symptoms or reversely 2) the cold virus somehow turns into the HHV6 virus. However, there could also be a third variable present. Perhaps a measure taken while one has a cold (such as medicine taken) can somehow spark an outbreak of this virus in some people? Or even chance could be present: that it is simply a coincidence that one has a cold and about a week later develops pityriasis rosea. There is not really any sign of what causes this consistent among all patients, making tests and studies difficult. What do you think? Do you think a virus, a third variable, chance, or something entirely different is causes the pityriasis rosea rash?


Hey I think that the common cold virus is most likely the cause of pityriasis rosea, only because the majority of the people tested were found to have had symptoms of a common cold prior to getting it. Because of what we have learned from class though I know that correlation does not equal causation so your third variable hypotheses are possible. I think that another third variable that could play a role in whether a person gets pityriasis rosea is how strong the person’s immune system is.

Have you ever thought that it’s possible that the chances are high for everyone to get pityriasis rosea but in general people have a strong enough immune system to fight it off. Therefore the participants may just happen to have a weaker immune system than the average person. Even though this is unlikely it is possible and could have definitely had an impact on the results of the observations.

As I stated earlier I believe the common cold virus is most likely the cause of the pityriasis rosea like you think. However I disagree with the possibility that the HHV6 virus was causal because the chances of people having this virus in the first place are slim. Most people are not walking around with a virus related to herpes. It is possible though the common cold virus can lead to the HHV6 virus provided certain factors like a person having an already weak immune system, and them not taking care of themselves while being sick. I agree with you that medicine could be a third variable because it wouldn’t be the first time that remedies have been suspected to be harmful. The same thing happened with Jenny McCarthy blaming her son’s autism on a vaccine. I doubt that it is possible that the majority of the people who had a common cold prior to getting pityriasis rosea got it due to chance.

I'm not positie what could cause this or what the third variable could be, however I do wonder if it's just dependent on the type of skin a person has. If it is a virus, maybe it's only people with extremely sensitive skin that get the actual rash. Maybe many people are walking around with this certain virus, but they do not show any symptoms besides the common cold because their skin is not as irritated. I, personally, have very sensitive skin in general. So I wonder if that could possibly make me more susceptible of getting this virus and having a rash like this?

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