The majority of people who think they are allergic to penicillin are actually not, according to new research.
Almost 95 per cent of the people who believed they were allergic to penicillin tested negative during a allergy test for the drug.
Often people had a bad experience with penicillin as a child but were never tested to see if they were truly allergic as they grew up, experts said.
Doctors also warned that sometimes people experienced a known side effect of the drug and mistook this as an allergy.
People mistakenly believing they are allergic to penicillin means they could be given alternative – sometimes less effective antibiotics – after surgery, researchers said.
It also means doctors have fewer options when selecting which antibiotic to use to treat a person's infection.
Penicillins are widely used to treat a variety of infections, including skin infections, chest infections and urinary tract infections.
The study comes after the World Health Organisation announced in April the world was facing a 'crisis' in antibiotic resistance, which they said is 'worse than the Aids epidemic'.
WORLD HEALTH ORGANISATION WARNS THAT ANTIBIOTIC RESISTANCE CRISIS COULD BE 'WORSE THAN AIDS'
Deaths from cuts and grazes, diarrhoea and flu will soon be common as antibiotics lose their power to fight minor infections, experts have warned.
The World Health Organisation says the problem has been caused by antibiotics being so widely prescribed that bacteria have begun to evolve and develop resistance.
It claims the crisis is worse than the Aids epidemic – which has caused 25million deaths worldwide – and threatens to turn the clock back on modern medicine.
The WHO warns that the public should ‘anticipate many more deaths’ as it may become routine for children to develop lethal infections from minor grazes, while hospital operations become deadly as patients are at risk of developing infections that were previously treatable.
Doctors are increasingly finding that antibiotics no longer work against urinary and skin infections, tuberculosis and gonorrhoea.
The WHO is urging the public to take simple precautions, such as washing hands to prevent bacteria from spreading in the first place.
Doctors are also being told to prescribe antibiotics sparingly and ensure patients finish the full course, as if they stop mid-way the bacteria may become resistant.
The crisis limits the choices of antibiotics available for prescription, and a perceived penicillin allergy adds further limitations, doctors said.
In the U.S., where patients pay for their prescriptions, they might be paying unnecessarily for more expensive drugs due to the perceived penicillin allergy.
Two studies were carried out to test the prevalence of misconceived penicillin allergies.
As part of the first study, 384 people who believed they were allergic to penicillin were given an allergy test.
The majority, 94 per cent, tested negative for penicillin allergy.
Lead author Dr Thanai Pongdee, from the Mayo Clinic in, Jacksonville, Florida, said: 'A large number of people in our study who had a history of penicillin allergy were actually not allergic.'
'They may have had an unfavourable response to penicillin at some point in the past, such as hives or swelling, but they did not demonstrate any evidence of penicillin allergy at the current time. With that in mind, their doctors prescribed different medications prior to surgery.'
In the second study, 38 people who believed they were allergic to penicillin were given penicillin skin testing.
Of the 38 people tested, all of them tested negative to an allergy for penicillin.
Often these patients, who believed they were allergic to penicillin, had been prescribed more expensive alternatives.
After discovering they were not allergic to penicillin the medical centre was able to change the medications of 29 of the patients, significantly lowering their prescription costs.
Dr Rob Hicks, a GP in London said the problem of a perceived allergy was known to doctors.
He said: 'It's my understanding that many people over the years have experienced unpleasant reactions to penicillin that are not always a true allergic reaction but may simply be a recognised side effect of the drug.'
'However, consequently they have either assumed or been told by their healthcare professional that they are allergic to penicillin.'
'It means there are fewer options when selecting a suitable antibiotic to treat a person's infection, particularly if there's also antibiotic resistance to one or more of the antibiotics that a person can take.
'It could mean it's harder to treat an infection, or if you run out of options, impossible.'
'True allergy to penicillin can result in mild symptoms but also can cause severe and potentially life-threatening allergic reactions so It's important that anyone with a penicillin allergy, or who believes they are allergic to penicillin, always let healthcare professionals looking after them, and friends and family, know this.'
The researchers advised patients that are told they have an allergy to something should be seen and tested by an allergist.
In the UK, patients who believe they are should go to their GP, who can perform a skin test to ascertain whether they are allergic to the drug.
The studies were presented at the American College of Allergy, Asthma and Immunology (ACAAI) Annual Scientific Meeting.
