When the Combat Methamphetamine Epidemic Act of 2005 passed, pharmacies moved all cold-medicine with the actually-works ingredient pseudoephedrine, only available on request and with a copy of your ID. In its place, the pharmacy shelves were restocked with phenylephrine, which was alleged to work just as well. It doesn't work at all.
Researchers have long been suspicious of the efficacy of phenylephrine, but studies were mixed. Now, thanks to a University of Florida study published in The Journal of Allergy and Clinical Immunology: In Practice, we know that phenylephrine is useless at the doses allowed over the counter; and may not work even at higher doses.
Thanks to the meth wars, cold medicine's effective ingredient isn't