Great study, but wrong conclusion: The Vapo Rub fail
© 2010 Roy Benaroch, MD
A study due for publication in December, 2010 claims to show that Vick’s Vapo Rub can help your child fight through the common cold. Though it was funded by the manufacturer (Procter and Gamble), it’s a good study—but if you read it carefully, there are some big red flags that say “Beware!” I don’t agree with the author’s conclusions, and I don’t agree with headlines in the media extolling the virtues of Vick’s. The study was well-designed, but the authors themselves found a fatal flaw that renders their results meaningless.
The study design was solid, and cleverly tried to prevent parents from being able to skew the results. 138 kids from age 2-11 years with at least moderate coughs were recruited. Children with more-specific causes of cough, like asthma, were excluded; and the children were not allowed to take other kinds of medication that might suppress a cough. The group was divided into thirds: one group received no treatment at all, one group received plain petrolatum (similar to Vaseline), and one group received Vick’s Vapo Rub. The parents were given a glass jar in an opaque bag with their study drug (or an empty jar, if they were in the no treatment group), along with a second jar that contained Vapo Rub in all three groups. When the families began treatment, they were instructed to first rub Vapo Rub under their own noses—then rub the study medication on their child’s chest. By putting Vapo Rub on the parents, the hope was that parents would not be able to tell whether they had put plain petrolatum or Vapo Rub on their child’s chest.
The next day, parents filled out a questionnaire, recording how well, or how poorly, their child did. The kids who received Vapo Rub did the best, especially when their ability to sleep was judged. That’s what the mainstream and medical press are reporting. But sometimes it pays to read the study a little bit further.
Thought the authors tried to prevent the parents from knowing what treatment group they were in, 90% of the parents correctly “guessed” what their child had been treated with the night before. I don’t know if the parents were able to smell past the Vick’s on their own noses, or if they didn’t follow directions, or if the approximately 50% of children in the Vapo Rub group who developed skin irritation gave it away—but in any case, this was essentially an unblinded study. Almost all of the parents knew whether their child was treated with Vick’s or the placebo—and that could certainly account for the observed differences in how the children did.
It’s human nature. The placebo effect has been documented in almost every clinical study that’s been done. People who are given what they think is medicine expect to get better, or expect their kids to get better, and will honestly judge that they did get better. Even if the “medicine” is itself just a placebo. Our own expectations influence our perceptions. If study participants are aware of whether they’re taking placebo or the study drug, clinical studies of medications are worthless.
There are other reasons to think twice before using Vick’s Vapo Rub. It can be quite toxic—according to the discussion section of this new study, an 8 tsp dose can kill a child. Much smaller doses are probably safe, but have occasionally been linked to seizures (children with seizures were excluded from the study.) In children less than two, Vick’s can cause serious lung irritation and breathing troubles.
When deciding whether to try a treatment, parents and physicians ought to weight the risks and the benefits. This study, in which the participants were inadvertently unblinded, allows us to draw no conclusions about whether Vick’s actually works. We do know that there are genuine risks. I’d stay away from Vicks, especially in younger children, until there is better proof that it actually works.
If you do want to try Vick’s Vapo Rub, follow the directions carefully. Do not put any near your child’s mouth, and do not use it in children less than two. Keep it way out of the reach of children and pets.