Phenylephrine - A conspiracy theory I believe
My conspiracy theory belief is that phenylephrine doesn't work as a nasal decongestant

One conspiracy theory I believe in is that [henylephrine doesn't actually work as a nasal decongestant.
What is Phenylephrine? It's the active ingredient in the cannot-be-turned-into-meth cold and flu medications that are sold in pharmacies in Australia.
During the original expansion of meth, a lot of meth was manufactured by converting pseudoephedrine into methamphetamines. Governments in various countries started pressuring drug companies to produce alternatives to pseudoephedrine cold and flu medication, and voila, phenylephrine was introduced.
My conspiracy theory belief is that given that everyone wanted to be helpful in trying to end the meth epidemic, no one looked too hard at the efficacy of phenylephrine.
In 2008, I was sold phenylephrine thinking it was pseudoephedrine and then discovering first-hand how ineffective phenylephrine is. Since then, I've been pretty convinced that phenylephrine is entirely ineffective at dealing with nasal congestion.
Alas, I have some vindication for this view, given that an FDA advisory released the following statement in 2023:
The committee discussed new data on the effectiveness of oral phenylephrine and concluded that the current scientific data do not support that the recommended dosage of orally administered phenylephrine is effective as a nasal decongestant.
Sadly, the wheels of justice turn slowly, and the phenylephrine is still available for sale. I look forward to my eventual vindication when phenylephrine is finally removed from pharmacy shelves in Australia.