One in five people in the UK believes that it can be beneficial to give your body a medicines "detox" by occasionally stopping your regular drug treatment for a long-term condition, a new study has found.

In fact, doing so can seriously impair health, and for someone with diabetes, asthma or depression, the results of doing so can be catastrophic, warns the National Pharmacy Association (NPA), which carried out the survey.

The poll also reveals that nearly a third of people in the UK believe it is OK to take non-prescription medicines that have been specifically recommended for someone else - whereas in fact this can be dangerous, even with common cough and cold remedies - and some people also think it is safe for children to be given adult medication provided that the dosage is reduced.

Other widely-held and potentially dangerous beliefs revealed by the survey are that 25% of people are under the impression that aspirin is just a weaker version of ibuprofen, while 50% think that the influenza vaccine can cause flu. This latter misconception is a long-standing myth that could stop some people who are in "at-risk" categories from getting the protection they need, says the NPA.

Moreover, millions of people in the UK could be using out-of-date medications. One in 10 of those surveyed told the Association that they never check to see if their medicines are still in date; however, drugs can become increasingly less effective once they pass their expiry date, the NPA points out.

"There is a lot of misunderstanding about how medicines work in your body - it's important to get the right treatment and the right advice," said Leyla Hannbeck, head of information at the NPA.

"We are especially concerned that people with long-term conditions may feel it is right to 'detox' from time to time, by taking a break from their prescribed medicines. For someone with, say, asthma, diabetes or depression, the result of doing so can be catastrophic," she warned.

The study was launched at the start of Ask Your Pharmacist Week, which aims to raise awareness of the range of services and expert advice available to people from their pharmacies.