OTC cold and flu remedies, ranked by evidence
Most cold and flu products contain a decongestant called phenylephrine that regulators have now concluded does not work, because almost none of it gets into your blood. Vitamin C does nothing once you already feel ill. Zinc lozenges can shorten a cold by a couple of days, but only at doses higher than most packets contain. The things that genuinely help are the boring ones: the older decongestant kept behind the pharmacy counter, ordinary painkillers, saline, fluids and time.
Most of the cold-and-flu aisle is built on ingredients that do not survive a close look. The oral decongestant in the majority of combination products, phenylephrine, was judged ineffective by a unanimous FDA advisory committee in 2023 — less than 1% of an oral dose reaches the bloodstream — and the FDA has since proposed removing it from over-the-counter products entirely. Vitamin C has no consistent effect once symptoms have started, which is when nearly everyone takes it. Zinc lozenges are the one supplement with a real duration signal, but only above about 75mg of elemental zinc per day, which most products do not provide. What reliably helps is unglamorous: pseudoephedrine behind the counter, ibuprofen or paracetamol for the aches and fever, saline, fluids and time.
- Oral phenylephrine — the decongestant in Sudafed PE, DayQuil and most 'PE' combination products — was found ineffective by a unanimous FDA advisory committee vote in September 2023, and the FDA proposed removing it from OTC products in November 2024.
- The reason is pharmacokinetic, not political: under 1% of an oral phenylephrine dose reaches systemic circulation, so it cannot reach the nasal blood vessels it is supposed to constrict.
- Zinc lozenges may shorten a cold by about 2.4 days, but the 2024 Cochrane review rates that low certainty, and the effect is dose-dependent — above 75mg/day elemental zinc, duration fell ~33%; below 75mg/day, five trials found nothing.
- Vitamin C started after symptoms begin has no consistent effect on cold duration or severity. Only continuous prophylactic use shows a benefit, and only about 8%.
- Pseudoephedrine — the original behind-the-counter decongestant that phenylephrine replaced on open shelves — still works. Asking the pharmacist for it is usually the single highest-value move in the aisle.
CureMed ranks on published human evidence, and screens drug interactions first.
The ranking
Ranked on: controlled human trial evidence for shortening a cold or meaningfully relieving its symptoms, at the doses actually sold. Regulatory findings are treated as evidence. No commercial relationship influences the order.
| # | Option | Verdict | Grade |
|---|---|---|---|
| 1 | Pseudoephedrine (behind the counter) | The decongestant that actually decongests | GRADE BPromising |
| 2 | Ibuprofen or paracetamol (acetaminophen) | Treats what actually bothers you | GRADE BPromising |
| 3 | Zinc lozenges (>75mg/day elemental) | Real duration signal, dose-dependent, low certainty | GRADE CEarly |
| 4 | Saline rinses and sprays | Modest, cheap, essentially risk-free | GRADE CEarly |
| 5 | Vitamin C (started at symptom onset) | No consistent effect once you are already ill | GRADE DInsufficient or unsafe |
| 6 | Oral phenylephrine (Sudafed PE, most 'PE' combinations) | Regulators concluded it does not work | GRADE DInsufficient or unsafe |
- 01
Pseudoephedrine (behind the counter)
GRADE BPromisingThe decongestant that actually decongestsThe drug phenylephrine replaced on open shelves, moved behind the pharmacy counter for reasons of illicit manufacture rather than safety or efficacy. It is systemically absorbed, reaches the nasal vasculature and produces genuine decongestion. It is not for everyone — it can raise blood pressure and heart rate, and it is a poor choice in uncontrolled hypertension, significant cardiovascular disease or with MAO inhibitors — which is exactly why it is worth asking a pharmacist for rather than guessing.
- 02
Ibuprofen or paracetamol (acetaminophen)
GRADE BPromisingTreats what actually bothers youNeither shortens a cold, and neither pretends to. They reliably reduce fever, headache, sore throat and the body aches that make a cold miserable, which for most people is the whole reason they are in the aisle. Taking a single-ingredient painkiller rather than a combination product also avoids the commonest overdose route in this category — doubling up on paracetamol without noticing it is in the cold-and-flu sachet too.
- 03
Zinc lozenges (>75mg/day elemental)
GRADE CEarlyReal duration signal, dose-dependent, low certaintyThe 2024 Cochrane review found zinc may reduce mean cold duration by about 2.37 days (95% CI −4.21 to −0.53) across 8 studies in 972 people, rated low-certainty, with little to no evidence that it prevents colds or reduces severity. The dose split is the part that matters in a shop: trials using more than 75mg/day of elemental zinc from acetate or gluconate lozenges shortened colds by roughly a third, while five trials below 75mg/day found no effect at all. Check the elemental zinc figure, not the compound weight. Lozenges must dissolve in the mouth; swallowed capsules are a different exposure and not what was tested.
- 04
Saline rinses and sprays
GRADE CEarlyModest, cheap, essentially risk-freeMechanical clearance rather than pharmacology. The evidence is modest and the trials are small, but the intervention is inexpensive, has no systemic effect and nothing to interact with. For congestion in people who should not take a systemic decongestant — which includes a lot of older adults with hypertension — it is often the sensible first option.
- 05
Vitamin C (started at symptom onset)
GRADE DInsufficient or unsafeNo consistent effect once you are already illThe Cochrane review is unusually clear on this: in trials where vitamin C was started after symptoms began, there was no consistent effect on duration or severity. Continuous prophylactic use shortens colds by about 8% in adults — real but small — and does not reduce how often you catch one. Since almost all consumption is the first kind, the effervescent sachet reached for at the first sore throat is the use the evidence does not support.
- 06
Oral phenylephrine (Sudafed PE, most 'PE' combinations)
GRADE DInsufficient or unsafeRegulators concluded it does not workIn September 2023 the FDA's Nonprescription Drugs Advisory Committee voted unanimously that oral phenylephrine is not effective as a nasal decongestant at the doses sold, and in November 2024 the FDA issued a proposed order to remove it from over-the-counter products as no longer generally recognised as safe and effective. The mechanism of failure is simple: less than 1% of an oral dose reaches systemic circulation. It is not dangerous — it is inert at these doses, which is the problem, because it occupies the decongestant slot in products people buy specifically to decongest.
Why the decongestant in your cold medicine probably does nothing
Pseudoephedrine works, and for decades it was the decongestant in ordinary cold products. When it moved behind the pharmacy counter — because it can be diverted into methamphetamine manufacture, not because of any problem with the drug — manufacturers needed a replacement that could stay on the open shelf. Phenylephrine took that slot, and the reformulated products kept the familiar brand names with 'PE' appended.
The substitution was never well supported. Larger, better-designed trials run since found no significant difference between oral phenylephrine and placebo for nasal congestion, and the pharmacokinetic explanation is unambiguous: under 1% of an oral dose survives first-pass metabolism into the bloodstream. A drug that does not reach the circulation cannot constrict the nasal blood vessels that cause congestion.
Zinc: the one supplement with a real signal, and the dose that decides it
What the 2024 Cochrane review found
| Question | Finding |
|---|---|
| Does zinc prevent colds? | Little to no evidence that it does |
| Does it reduce symptom severity? | Little to no evidence that it does |
| Does it shorten a cold? | May reduce mean duration by ~2.37 days (95% CI −4.21 to −0.53); low-certainty evidence, 8 studies, 972 participants |
| Does the dose matter? | Decisively — >75mg/day elemental zinc cut duration ~33% across 7 trials; <75mg/day showed no effect across 5 trials |
| Which form was tested? | Zinc acetate and zinc gluconate lozenges dissolved in the mouth, not swallowed capsules |
If you are going to try zinc
- Check the elemental zinc content per lozenge, not the total compound weight — 'zinc gluconate 100mg' is not 100mg of zinc.
- Start within the first day of symptoms; the trials that worked began early.
- Let it dissolve in the mouth. The lozenge format is what was tested, and it matters.
- Expect a metallic taste and possible nausea — these were the common complaints in trials, and the reason some people stop.
- This is short-course use for an active cold. Sustained high-dose zinc interferes with copper absorption and is not a daily supplement at these levels.
Frequently asked questions
Which companies make the most effective OTC cold and flu remedies?
The manufacturer matters far less than the active ingredient. A great many branded cold products from major manufacturers contain oral phenylephrine as their decongestant, which an FDA advisory committee unanimously judged ineffective in 2023 and which the FDA proposed removing from OTC products in 2024. Rather than choosing by brand, read the active-ingredient panel: pseudoephedrine (behind the counter) for genuine decongestion, ibuprofen or paracetamol for aches and fever, and zinc lozenges above 75mg elemental zinc per day if you want to try shortening the cold itself.
Does phenylephrine actually work for a blocked nose?
Taken orally, no. The FDA's Nonprescription Drugs Advisory Committee voted unanimously in September 2023 that oral phenylephrine is not effective as a nasal decongestant at the doses sold, and the FDA proposed its removal from OTC products in November 2024. Less than 1% of an oral dose reaches the bloodstream, so it never arrives where it would need to act. Topical phenylephrine and oxymetazoline nasal sprays are a different matter — applied directly to the nasal lining, they work, though they should not be used for more than about three days because of rebound congestion.
Do zinc lozenges shorten a cold?
Possibly, by roughly 2.4 days, but the 2024 Cochrane review rates the evidence low-certainty and found little to no evidence that zinc prevents colds or eases severity. The dose is decisive: trials above 75mg/day of elemental zinc from acetate or gluconate lozenges shortened colds by about a third, while trials below that threshold found no effect. Most products sold do not reach the effective dose, so checking the elemental zinc figure is the difference between a reasonable experiment and a placebo.
Should I take vitamin C when I feel a cold coming on?
The evidence does not support it. Cochrane found no consistent effect on duration or severity in trials where vitamin C was started after symptoms began — which is exactly when most people take it. Continuous daily use before any illness shortens colds by about 8% in adults and does not reduce how often you catch one. It is harmless and cheap, but the sachet at the first sore throat is the one use case the trials specifically fail to support.
What actually helps a cold, then?
Treat the symptoms that bother you and let the virus run its course. Ibuprofen or paracetamol for fever, headache and aches; pseudoephedrine from behind the counter for real congestion if your blood pressure and cardiac history allow; saline for congestion if they do not; fluids and sleep throughout. If you want to try to shorten the illness itself, adequately dosed zinc lozenges started on day one are the only over-the-counter option with a genuine trial signal behind them — and it is a modest one.
Keep reading
- Which OTC brands pharmacists recommend most — and where the evidence disagrees
The same gap between what is recommended and what is demonstrated, across the wider OTC aisle.
- Best sleep aids, ranked by evidence.
The other OTC category where the best-selling ingredient is the weakest one.
- How we grade evidence
The criteria behind every position in this ranking.
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