"When you're a winter Olympian, it's always cold and flu season."

That's the gist of a new ad for Vicks DayQuil featuring Olympic skier Ted Ligety. But with the stringent rules around performance-enhancing drugs, can Ligety even take the product he's endorsing?

The answer is yes… for now.

While the World Anti-Doping Agency prohibits the use of certain decongestants, phenylephrine - the drug found in DayQuil - is only part of the " 2014 Monitoring Program." That means it's OK for Sochi, but could be banned by the 2018 Games in PyeongChang, South Korea.

Check out our performance-enhancing drug cheat sheet.

Phenylephrine works by reducing the swelling of blood vessels in the nasal passages. The drug's cousin, pseudoephedrine, does the same thing, but its stimulant effects land it on WADA's prohibited list in urinary concentrations greater than 150 micrograms per milliliter.

Pseudoephedrine was part of WADA's monitoring program in 2008, and was reintroduced to the prohibited list in 2010 "based on the results of controlled excretion studies as well as scientific literature."

Athletes are advised to stop taking pseudoephedrine-containing drugs like Advil Cold and Sinus and Zyrtec-D at least 24 hours before competing to allow the drug to clear from the body, but WADA is still monitoring pseudoephedrine in smaller concentrations.

Caffeine and nicotine are also part of the 2014 monitoring program.

Vicks did not immediately respond to requests for comment about the new ad campaign and the 2014 Monitoring Program. Another prohibited decongestant, levmetamfetamine, is found in Vicks Vapoinhaler.

A Vicks DayQuil ad features Olympic skier Ted Ligety. (Image credit: Butter. music + sound/Vimeo)