Most medicines and tablets to treat sore throats, colds, flu, stomach troubles and various other illnesses are a waste of money, an investigation by 60 Million Consumers has found.
The group looked at 61 medicines that are sold over the counter in France without customers needing a prescription.
On those they tested 28 were considered to have side effects so severe they were classed as dangerous.
Certain medications were found to have effects that actually made things far worse than the original condition they were designed to treat.
There were examples of skin creams which could lead to sleep problems if used regularly and pills to unblock noses containing pseudoephedrine, that carries the risk of causing cardiovascular problems.
Helene Berthelot, a pharmacist who supervised the report also talked of patients being admitted to hospital with intestinal bleeding after taking too many tablets for a sore throat.
The effectiveness of as many as 20 others was either “weak or not proven” although at least they rarely had any undesired effects.
Only 13 medications like the medicine Clarix, Vicks vaporub, Imodiumcaps and Gaviscon were judged to be effective in treating the condition.
“We are in favour of self-medication but only if the user is well informed about side-effects and method of use and the products are perfect,” said Thomas Laurenceau from 60 Million Consumers.
"Over the years we have noticed more and more undesired side effects, it's very worrying."
The magazine says customers should be really aware of their symptoms before purchasing the medication, normally be in good health and only take then for a limited amount of time.
In France around 2,500 medicines are available over the counter but in many cases customers are badly informed about them and the risks they carry, for examples Strepsils Lidocaine for sore throats and Contalax, for constipation.
Berthelot says pharmacists can make a lot of money from over the counter medicines, but they should still sell the correct products.
The list of 28 medicines to be avoid according to 60 Millions Consumers.