A cure for the common cold has eluded medics for decades.
Now, scientists believe sucking on a zinc lozenge may be the answer to sufferers' prayers.
Taking lozenges which contain the mineral shortened the length of a cold from seven days to around four, research suggests.
The lozenges are commonly found in pharmacies and health shops - but people had to take one every few hours to see any effect.
In common colds, the virus may grow in the throat, which is why using lozenges may work better than swallowing pills, researchers said.
"Ordinary tablets that enter directly into the stomach, without releasing zinc in the pharyngeal [throat] region, are not effective," said lead author Dr Harri Hemila, of the University of Helsinki.
Zinc is important for the immune system and eating too little in the diet is known to increase the risk of infection.
The latest findings confirm previous studies by Dr Hemila's team, as well as those by Cardiff University's Common Cold Centre.
The team reviewed the available evidence on zinc and colds.
Previous research showed using low-dose zinc acetate lozenges had found no effect on the illness.
So Dr Hemila only looked at trials where patients took more than one lozenge, delivering a total of 75 milligrams (mg) of zinc or more per day.
They found three trials where people were randomly assigned either zinc acetate lozenges giving a high dose of the mineral or a placebo.
One trial also looked at differences in results for people with and without allergies.
The trials had a total of 199 people, who were were mostly female and between 20 and 50 years old. One third had allergies, including allergies to grasses, trees and pets.
They were instructed to have a lozenge every two to three hours and the lozenges took about 15 to 30 minutes to dissolve.
Overall, the average dose of zinc was between 80 and 92 mg of zinc per day.
The review found that patients who used zinc lozenges experienced colds that were almost three days shorter on average compared with the week-long colds of the group given a placebo.
The effect of the zinc lozenges was not altered by a person's allergies, smoking or how severe the cold was, researchers found.
And the results were also similar across age, sex and ethnic groups.
"This is a very important subject to study because the common cold is a very common problem and it leads to loss of work as well as disability because people are not able to focus," said Dr Meenu Singh, a professor of pediatrics at the Postgraduate Institute of Medical Education and Research in Chandigarh, India.
Dr Singh, who was not involved in the study, told Reuters Health while these results are promising, there are some side effects of zinc that need to be explored before high doses of zinc are available over the counter, rather than the current lower-dose ones.
For example, in previous studies, when zinc was inhaled it cause people to temporarily lose their sense of smell.
This means lozenges could dampen taste as well, Dr Singh said.
Some people also complain the lozenges leave a metallic taste in the mouth, he added - although the Finnish researchers said this wasn't a problem in the studies they reviewed.
"There is information now available that zinc in a higher dose could reduce your cold by a certain duration, but there is an added discomfort of taking lozenges," Dr Singh said.
"The tablets are large and need to be taken continually throughout the cold to be effective".
Dr Hemila warned that people with a cold should look for lozenges that do not contain citric acid, which can prevent the release of zinc into the body.
"Common cold patients should try zinc lozenges with doses about 80 to 100mg per day very soon after the onset of the common cold," Dr Hemila advised, adding that the lozenges can be used for one to two weeks of treatment.
The study was published online in the British Journal of Clinical Pharmacology.