Actually, products like Tylenol Sinus, Sudafed PE, Advil Sinus & Pain and others containing the supposed decongestant phenylephrine may work worse than a placebo, since cold medicine often comes with unpleasant side effects like jitteriness and dry mouth, and can leave you feeling worse than you did before taking it.
"It's a ripoff," said Leslie Hendeles, a professor of pharmacy and pediatrics at the University of Florida wrote in an editorial which accompanied the study published in the Journal of Allergy and Clinical Immunology: In Practice in September . "Right now, people with a stuffy nose deserve to get relief from an effective medicine."
Notably, the study was funded by pharmaceutical giant Merck, but Hendeles receives no funding from Big Pharma.
It’s not the first time that phenylephrine has been shown to be largely ineffective. Acoording to the Washington Post:
One study showed that majority of the drug is broken down in the gut and the liver, flushed out of a person's system before it makes it into the bloodstream. A 2009 study that will sound especially sinister to anyone who suffers from allergies put 39 patients with a grass allergy into a sealed room called the "Vienna Challenge Chamber." Then, the scientists piped in grass pollen. The people were given phenylephrine, a sugar pill, or another decongestant called pseudoephedrine. Phenylephrine did no better than placebo, while pseudoephedrine -- which must be obtained by going to the pharmacist's counter -- beat them both.
The enormous market of over-the-counter drugs for people with respiratory ailments—estimated at $1.1 billion in annual sales in 2014—keeps Big Pharma in the business of selling drugs that apparently do little to relieve suffering. Going behind the counter incurs all sorts of additional costs, so pharmaceutical makers are reluctant to do that. The ingredient pseudoephedrine can be used to make methamphetamine and is subject to much more federal regulation, which is why companies started using phenylephrine in their decongestants instead.
At any rate, cold and allergy sufferers are better off with chicken soup.