One in three people in the UK does not know the difference between common painkillers such as aspirin, ibuprofen and paracetamol, a survey suggests.
Many people just reach for the first pills available
The survey found 39% of women will consider what type of medicine to take, compared with only 27% of men.
The Panadol survey found a third of the 1,122 people questioned take the first medicine available for a headache.
Experts recommend that people first use paracetamol as a painkiller because it is gentler on the stomach.
Women were also shown to have better knowledge of pain relief, with 51% of women aware of the painkillers which can be inappropriate for those with heart problems, asthma or digestive disorders - compared with 41% of men.
Paracetamol: Painkiller, used to bring down temperature
Aspirin: Anti-inflammatory, reduces temperature, can cause gastric irritation, should not be given to under-16s
Ibuprofen: Similar to aspirin but fewer side effects
And while 89% of people knew painkillers can be unsuitable for individuals with medical conditions, more than 40% did not know which ones could pose a danger.
Hooman Ghalamkari is a community pharmacist in Worcester and said many people often ask for a painkiller by name, without considering what its ingredients are.
"There are many people who come into my pharmacy who have heard of a painkiller and just ask for it by brand name.
"They will also say that someone has recommended a certain brand to them but they still won't know what's in it, and won't even ask.
"There are issues with people not knowing what's in their medicine. If someone has asthma, for example, then taking aspirin or ibuprofen could make it worse.
"And if someone is already taking medicine prescribed by their doctor then taking further painkillers could mean they inadvertently take an overdose."
Mr Ghalamkari says information is available for people who wish to find out more about their medicines.
"There are safeguards in a pharmacy because as professionals we can advise people. But you can also buy these painkillers in supermarkets where are aren't the same safeguards in place."
Dr Chris Steele, a GP in Manchester, says paracetamol should be the "first choice painkiller" for most people.
"Paracetamol is gentler on the stomach and is an effective painkiller, so should always be considered first of all," he said.
"We have an excellent selection of painkillers available but there's a lot of confusion out there amongst the public.
"It's important that people are aware of the medicines they're taking because sometimes the painkillers they use can react with other medicines or make existing health problems worse."
Of those questioned in the survey sample, 41% of men do not take any pain relief, compared with 24% of women.
And the research claims that employees cost UK business £4.6bn in days off work due to common pains such as headaches, backache, period pains and toothache.
The survey was launched to coincide with Ask About Medicines Week, a campaign which encourages the public to ask more questions about medicines as they get older.
Figures from 2004 show that up to 10% of hospital admissions could be down to older people taking medicines that cause adverse reactions when combined.
Around half of older people at any one time are estimated to be taking drugs not as intended.
A leaflet entitled Ask About Pain Relief has also been produced containing advice on the use of painkillers.