Cold & flu remedies: What works and what doesn’t

We've looked at the evidence behind more than 50 products.

Various healthy natural products for immunity boosting and cold remedies on white background.

There are big bucks to be made selling cold and flu remedies. Last year, Kiwis forked out $38 million at the supermarket on pills and potions for fighting winter bugs.

We looked at more than 50 cold and flu products, from decongestants and antihistamines through to cough drops, to find which offer the most effective relief from winter ills. Considering the hefty price of some products, you might think there’s strong science supporting their effectiveness. But we found it’s often less than convincing.

Oral decongestants

With pseudoephedrine absent from the shelves since 2011, there’s just one decongestant ingredient in cold and flu tablets and elixirs – phenylephrine.

It’s frequently combined in a tablet with paracetamol and marketed under a variety of names, including Codral Relief, which claims to have “a non-drowsy formula for relief of headaches and fever, blocked and runny nose, body aches and pain”.

Three US clinical trials published in the past decade concluded phenylephrine was no better at relieving congestion than a placebo.

Lemsip touts its Cold & Flu with Decongestant capsules as “a quick way to get effective relief from symptoms such as headache, body aches, blocked nose, fever, and sore throat”.

Manufacturers’ claims that phenylephrine may clear congestion date to trials done 40 to 60 years ago. But only half of these trials showed phenylephrine was effective. Three US clinical trials published in the past decade concluded it was no better at relieving congestion than a placebo.

There’s more evidence the paracetamol will relieve your bunged-up nose than the decongestant. You’ll also save money by sticking with the medicine-cabinet staple. A two-pill dose of the painkiller-decongestant tablets we looked at were, on average, three times the price of plain paracetamol.

When we asked companies for evidence to support claims for phenylephrine, the results were underwhelming.

The New Zealand Self Medication Industry Association (NZSMI) – the PR representative for major maunfacturers such as Reckitt Benckiser (Nurofen, Lemsip) and Bayer (Demazin) – offered a decade-old study showing phenylephrine working in four out of eight trials.

Others pointed to Medsafe’s registration of the ingredient for use as a decongestant. Multichem (which produces the Ethics range) ignored our requests.

No company alerted us to the recent US clinical trials showing phenylephrine was no more effective than a placebo at relieving congestion. Even Bayer, which sells Demazin-brand medicines with phenylephrine and which sponsored two of the studies, didn’t mention them.

Bottom line: Good evidence is yet to emerge supporting phenylephrine’s effectiveness as a decongestant.

Cough medicines

Cough medicines fall into two categories: dry cough remedies, which use a cough suppressant such as dextromethorphan or pholcodine, and chesty cough remedies, which typically use the expectorant guaifenesin.

If you’re suffering from a dry cough, Vicks Formula 44 Dry Cough promises “long-lasting cough relief”, while Duro-Tuss Forte says it “relieves a stubborn dry cough”.

Independent reviews have found little if anything to support the claims for cough medicines.

On the chesty side, Benadryl Chesty Cough & Nasal Congestion says it will “relieve chesty coughs … fast”. Robitussin’s Chesty Cough formulation “loosens and helps clear chest congestion”, according to the box.

However, independent reviews have found little if anything to support the claims for these ingredients. A 2014 study by the Cochrane Collaboration, which conducts systematic reviews on healthcare, cautiously concluded there was “no good evidence for or against” their effectiveness.

The review also questioned how the products “can continue to be promoted using language that implies that their effectiveness is not in doubt”.

In support of product claims, the NZSMI and Procter & Gamble (Vicks) sent us a study on dextromethorphan, which concluded more research into the active ingredient’s effectiveness is a good idea. They also sent us research where artificially stimulated coughs were successfully suppressed.

Radiant Health, which sells pholcodine in the Duro-Tuss range it distributes, pointed to a 2012 European Medicines Agency review that noted there was “a large body of data demonstrating the effectiveness of opioids in the management of non-productive cough”. However, Cochrane Reviews have not found the evidence conclusive for pholcodine.

Six recent international clinical trials on over-the-counter cough formulations containing dextromethorphan or guaifenesin also did not demonstrate they work. That’s despite their high price: products we looked at ranged from $12.99 to $28.99.

GlaxoSmithKline (Panadol, Coldrex), Pfizer (Dimetapp, Robitussin), Procter & Gamble and Reckitt Benckiser (Mucinex, Strepsils) all sponsored at least one of these studies but none mentioned them in replies to us.

The only ingredient for which studies show some support is the expectorant bromhexine, found in some Benadryl, Bisolvon, Dimetapp, Duro-Tuss and Robitussin formulations. However, evidence for its effectiveness is largely based on trials involving people suffering from long-term respiratory disease rather than a winter bug.

Bottom line: If you’re considering a cough medicine, keep an eye on the ingredients and be aware that you may be getting nothing beyond the placebo effect.

Double dosing

The same ingredients pop up repeatedly with over-the-counter cold remedies, which places consumers at risk of double or triple-dosing.

For example, if a patient took 2 capsules of Codral’s Cold, Flu & Cough Day or Night, a dose of Vicks Formula 44 Dry Cough Syrup and followed it with a Strepsils Dry Cough Lozenge, they would receive the drug dextromethorphan in three ways.

Overuse of the medication can cause breathing problems, vomiting and convulsions.

Too much paracetamol is also risky and can lead to liver failure. Paracetamol is commonly found in cold and flu sachets, such as Lemsip and Codral Relief varieties.

Bottom line: Always check the list of active ingredients before you buy – and take – over-the-counter medication. Medsafe requirements mean many over-the-counter products must carry a warning about the risks of taking more than one medicine at a time.

Antibacterial and antiviral action

A standard cold or bout of flu is caused by a virus, not bacteria. But that hasn’t stopped manufacturers adding antibacterial agents and spruiking their benefits.


The Strepsils range boasts on packs it has “double antibacterial action”. Ethics Medicated Throat Lozenges uses the same phrase, and emphasises the product provides “symptomatic relief of sore throats and mouth infections”. Codral and Difflam also sell lozenges touting the antibacterial agents in them.

While sucking a throat drop will increase the flow of saliva and soothe your throat, you’d get the same effect from a lolly or a spoonful of honey. The anti-inflammatory and anaesthetic agents in some products may numb a painful throat, but their antibacterial ingredients won’t do anything to help cure your cold.

Despite the antibacterial hype on the front of the packs, the Codral and Strepsils ranges have a disclaimer on the back that states, “the efficacy of an antibacterial agent in lozenges in reducing the severity or duration of throat infections has not been clinically established”. Difflam packs carry a similar warning, but Ethics brand lozenges stay mum.

Hand washes

There’s little point buying products such as antibacterial hand washes if you’ve got a cold or flu. According to the US Centers for Disease Control and Prevention (CDC), it hasn’t been proved these hand washes are any better at stopping the spread of infection than similar products without antibacterial chemicals.

There’s also a risk they could do harm. The CDC says laboratory tests have shown a link between antibacterial chemicals in cleaning products and bacterial resistance. However, further research is needed to determine whether these products may contribute to bacterial resistance outside of the lab.

Antiviral tissues

Feel free to stick with regular tissues. The idea of a three-ply tissue with a middle layer of citric acid and sodium lauryl sulfate to kill viruses was first put to the test in a series of trials in the 1980s. The results were disappointing – the technique managed to cut down transmission from one person in the house to another, but overall these families still caught just as many colds as the ones using tissues with a placebo.

The tissues can cost up to four times the price of others. Regular hand washing with soap and water, in and away from the home, and covering your mouth when you cough or sneeze are the best techniques to prevent transmission of common cold germs. The vaccine remains your best bet for avoiding the flu.

Bottom line: Antibacterial and antiviral additives will do little to prevent you from catching a cold, or relieve your symptoms once you have one.

Natural remedies

Vitamins and extracts are often promoted as being able to both prevent the common cold as well as shorten the length of time you’re sick. But the jury’s still out on most products.

Probiotic supplements

There are signs regular use of “good bacteria” may ward off illness and help a person recover more quickly. A 2015 Cochrane Review found taking a probiotic supplement in a tablet or dairy product appeared to halve the number of colds a person had and cut the duration of these bugs by nearly two days. However, the experts had misgivings about the quality of the trials and considered the evidence low.


The herb is often found in supplements purporting to boost the immune system. But systemic reviews have found only one good-quality study showing garlic supplements lower a person’s risk of developing a cold. More research is needed.

Vitamin C

Research has failed to demonstrate the vitamin offers any benefit in either prevention or treatment of winter bugs, beyond that of the placebo effect. The sole exception is for people under physical stress, such as high-performance athletes.


There is some evidence that regular use of these supplements can slightly reduce the risk a person will experience a cold. However, this benefit appears to be weak.

Bottom line: There’s no good evidence showing regular use of supplements will reduce your chances of catching a cold. Product claims for supplements have leapt ahead of the science.

What may work

There are cold and flu remedies that have better evidence behind them. And they’re often cheaper options.

Nasal sprays

The blood vessels in your nose swell up when you catch a virus, contributing to that “bunged up” feeling, alongside the extra mucus your body produces. Nasal sprays encourage these blood vessels to constrict or nasal glands to reduce the mucus produced. Studies suggest sprays with ipratropium bromide, such as Atrovent Nasal and Otrivin Plus, may offer relief from congestion, while oxymetazoline, used in Dimetapp, Drixine, Sudafed and Vicks Sinex, and xylometazoline, used in Otrivin, may also provide relief, albeit modest. Nasal sprays are also cheaper than painkiller-decongestant pills. The downside of nasal sprays is that you must stop using them after a certain time (usually three to five days) or risk “rebound congestion”, when a blocked nose returns after you cease using the product.


Some over-the-counter cold and flu tablets combine paracetamol with an antihistamine and a decongestant. Antihistamines appear to offer some cold sufferers a short-term boost. As they do for allergy sufferers, antihistamines block the body chemical histamine, which causes runny noses, watery eyes and sneezing. If you choose an ordinary antihistamine pill you’ll pay, on average, $1.51 a day, compared with $5.40 for combination cold pills with an added antihistamine.

Paracetamol, ibuprofen and aspirin

These everyday painkillers can offer relief from the aches and discomfort of winter bugs.


The jury is still out but there are small studies that have found honey can relieve symptoms and help children sick with the common cold sleep better.

A doctor’s note

University of Auckland medical professor Bruce Arroll says the best thing you can ask your doctor for is a sick note instructing you to take a few days off work. This stops you passing the virus to the outside world. There’s no cure for the common cold and most prescription medicines won’t offer anything more than a placebo effect.

Bottom line: A few days of R&R remains the best prescription for recovery. Your cold should clear up within a week, though a cough may last a month. Flu can linger up to a fortnight. If your symptoms are severe, see a doctor.

GUIDE TO THE GRAPHICS PRICE is based on the recommended dose of a medication or combination, and averaged across a range of brands. Prices were collected in a store survey conducted in March 2017.

Which remedies are effective?

What are the rules?

Consumers rely on health agencies to ensure they’re not wasting their money on something that doesn’t work the way it claims.

Medsafe, the Ministry of Health’s medicines-safety agency, is tasked with ensuring medicines are safe and effective, and of high quality.

So what is Medsafe’s view of over-the-counter decongestant and cough remedies?

Medsafe group manager Chris James says medicines for treating the symptoms of a minor illness have a different bar to pass than a drug for a life-threatening condition – and a medicine’s effectiveness is weighed against its safety risks.

“If new data is showing the benefits [for the formulations] do not outweigh the risks any more, we’ll be taking regulatory action.

“From what we’re seeing at the moment, we consider the benefits still outweigh the risks for these products for the population. That’s not to say that we’re not looking at what’s coming through … at the Cochrane Reviews and the studies. We’ll be paying very close attention to what some of the big regulators in the world are doing,” he says.

We’ve asked Medsafe to review the efficacy and marketing of these medications. We believe regulations should require a higher standard of evidence for over-the-counter medications than what’s currently accepted.

Unsafe for under 6

Unsafe for under 6

17may cold and flu under 6 promo

Unsafe for under 6

The risk of adverse effects means Medsafe recommends the following substances are not given to children under the age of 6:

  • Cough expectorants guaifenesin or ipecacuanha
  • Cough suppressants dextromethorphan or pholcoldine
  • Decongestants phenylephrine and pseudoephedrine
  • Antihistamines brompheniramine, chlorphenamine, diphenhydramine, doxylamine, promethazine or triprolidine

Member comments

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Francois D.
16 Aug 2019
How about Zinc Lozenges?

I saw mush news and research about the effectiveness of zinc lozenges while living in the US. It seems that these somehow limit the virus' ability to multiply - thereby shortening the cold. I was very surprised to see that these products are not on the shelves at pharmacies - curious why not, as in my experience they really seemed to work.

Consumer staff
19 Aug 2019
Re: How about Zinc Lozenges?

Hi Francois,

Thanks for the question. While some studies found zinc could have promise, unfortunately, there isn’t a reliable answer on this one - yet. The Cochrane Collaboration, which systemically reviews all the available medical research, is currently analysing the evidence for zinc’s effect on the common cold. We’re keeping an eye on this review and hope to include the results once they’re available. Sorry not to be more help!


Olivia - Consumer NZ writer

Sarah L.
13 Jun 2017
Vicks inhalers

Hi great article thank you just wondering about the benefits of the vicks chest rubs and Inhaler sticks? We're they not included in any tests? Thanks. Sarah

Previous member
13 Jun 2017
Re: Vicks inhalers

Hi Sarah,

We primarily looked at cold and flu medications, those with approved drugs that are absorbed by the body for symptom relief. Therefore, we didn’t look at inhalants, and the Cochrane Collaboration hasn’t reviewed the subject. However, there are a few studies out there (such as this one: that have found cold sufferers using the chest rubs feel their nose has cleared and/or can sleep better.

One interesting study (that has been subject to some debate) is this one: It found that the feeling of relief from inhaling the vapours may just be a subjective experience — in reality the rub may make your body produce more mucus. However, it’s important not to read too much into one study. A key thing to remember is that (unlike the inhaler sticks designed for the nose) Vicks advises you to only use the rub on your chest and throat, not under your nose. I hope that’s helped!

Kind regards,
Olivia – Consumer NZ staff member

Christina R.
22 May 2017
Any addictive cough medicine ingredients?

I have read about people overseas becoming addicted to cough medicines. Are any sold in NZ that contain addictive ingredients?

Previous member
22 May 2017
Re: Any addictive cough medicine ingredients?

Hi Christina,

It’s possible that the substance you read about was codeine, which can be addictive. Codeine is added to some cold and flu products in New Zealand, typically the pills you buy over the counter. However, Medsafe is currently considering whether to put further restrictions on the sale of codeine. Overseas, the cough medication dextromethorphan (which you’ll find in dry cough syrups in NZ) has been known to be abused, but scientists aren’t yet sure if it is a physically addictive substance.

Kind regards,
Olivia - Consumer NZ staff

Jan M.
17 May 2017
great article

thanks for this - a great article and really good to have confirmation about effective remedies.

Lewis B.
15 May 2017

Ginger has also been used to treat the common cold in China for thousands of years. No studies on this?

Previous member
18 May 2017
Re: Ginger

Hi Lewis,

Thanks for your question. The gold-standard clinical trials we’ve seen for ginger as a natural remedy tend to focus on nausea. Ginger didn’t really pop up in our research on the common cold, except being mentioned as a Chinese remedy. The Cochrane Collaboration hasn’t looked into this area, as they have for Echinacea and garlic for the common cold, for example. It may be an area that researchers haven’t thought to invest the money for a robust trial yet.

Olivia - Consumer NZ staff

George L.
14 May 2017
UK Research

After searching for a cure for the common cold for many years the Cold Research Centre based at Salisbury in England was only able to come up with the suggestion that taking extra vitamin C and zinc might shorten the duration of the cold.

Alan F.
14 May 2017
Good Article

Couldn't agree more with the article findings, phenylephrine is useless, a complete waste of money.
I head straight to the doc for a prescription of sudomyl.

13 May 2017
I agree with this article

Octrivin is brilliant. I just use the junior one... does the job well. And in only one nostril...(too much information??) ... I find extends how long I can use it.

Previous member
13 May 2017

A friend of mine, who is a retired doctor told me a few years ago that zinc is the only thing with proven impact. Did you look at this?

David H.
13 May 2017
+1 for Zinc

I'm pretty sceptical about most supplements but zinc really does seem to lessen the length and severity of any colds I catch. The virus always used to end up in my lungs, much to the 'delight' of those who had to put up with my coughing, but ever since taking zinc at the first sign of a cold, it hasn't been a problem. I still get the cold but it never lasts as long as it used to. New Scientist also ran a comparative article ( which said there was some evidence for the efficacy of zinc supplements.

Previous member
15 May 2017
Re: Zinc?

Hi Lesley,

There has been a bit of uncertainty over the science on zinc for the common cold. We rely on the experts at the Cochrane Collaboration and their assessment of the scientific trials of natural remedies. A few years ago, Cochrane released a review of the research for zinc and did conclude the mineral was effective at helping people fight off a cold.

However, last year (after a number of errors in the review were pointed out) Cochrane withdrew this review. Because of this complex situation, we decided not to comment on zinc in the article, but will update it the next time Cochrane re-reviews the trials. We didn’t want to guess for ourselves what this withdrawal meant (you can read more here: It may be that the next review comes to an entirely different conclusion or that it simply finds that zinc is effective, but the experts aren’t as confident in that conclusion as they were previously. I hope that has helped to answer your question.

Olivia - Consumer NZ staff

Steven P.
08 May 2017
Pseudoephedrine was a very effective decongestant - lets have it back again

Whilst the P drug is a serious problem, surely pseudoephedrine can be made into a tablet that remains effective yet is extremely difficult to extract and make P from?

Then we could go back to having an effective cold symptom reliever. I used to simply take paracetamol and sudomyl 60mg tablets. When a cold was heavy I could 3 tablets a day (morning/lunch/night) and as you "dried up" and the cold became less you could drop that 2 tablets morning/night and then 1 tablet at night and finally none.

You could buy 60 x sudomyl tablets for ~$10 and it was HIGHLY effective.

The modern cold remedies are just rubbish. This consumer article reinforces for me what I already believed.

I hope there is a way that pseudoephedrine can be delivered that will make it very difficult to extract. The first drug company that can come up with a good format will make a fortune - an effective cold symptom reliever back on the market.

You can still get sudomyl 60mg tablets from the doctor, but, you get the Spanish inquisition and they will only supply very small quantities (10 tablets) at a time.

The few have wrecked it for the many!

13 May 2017
best way to prevent extraction

Agreed. Looking at P usage worldwide, it's problematic in deprived communities. In order to have effective cold medications again, voters need to seek policy that reduces social inequity

Jo R.
26 Aug 2020
Discontinued too

The alternative Sudomyl you mention has now been discontinued too. So far the only working alternative found is kiwi made Rocket Fuel by SavvyTouch. Does not fix sinus like sudomyl but it helps to relieve, which is more that a lot do and it its natural

H W.
04 May 2017
Kaloba works..medically proven

You missed Kaloba. Clinically tested in medical is a natural antiviral with proven efficacy and now registered as a medicine in some countries. Safe for kids. My family have used it for years

Previous member
08 May 2017
Re: Kaloba works..medically proven

Hi there,

Thanks for your comment. The 50 products we looked at were based off common cold & flu ingredients sold in supermarkets and pharmacies (the ones consumers were most likely to buy) and Kaloba didn’t pop up.

While Cochrane have looked at it, most of the scientific evidence it examined concerned chest and sinus infections, rather than the common cold:

Olivia – Consumer NZ staff

Andrew Crosby
04 May 2017
Spoilt by idiots

10 years ago we had an effective decongestant​, sadly some idiots decided it was just the thing to get high on, could we try to get it back some how? A national purchase register sounds to me like a great idea...

Paul W
07 May 2017
May as well take sugar pills

I agree. Now days you pay about $18 for what basically amounts to sugar pills. No use whats so ever. Thanx to the current Government on banning the stuff that worked

04 May 2017
Fair Trading Act?

Have you referred your findings to MBIE? Isn't this similar to the Nurofen claims?

Previous member
04 May 2017
Re: Fair Trading Act?

Hi Simon,

While the Fair Trading Act protects consumers from misleading claims, there’s also protections in the Medicines Act specifically prohibiting misleading claims on medicines. Because of this, we think Medsafe, who is responsible for enforcing this legislation, is the appropriate agency to investigate. We’re keen to see how they respond to the request we’ve made for them to review both the marketing and benefit-risk ratio of these products.

Olivia - Consumer NZ staff