People with penicillin allergies are more likely to get superbugs

People diagnosed with penicillin allergies are far more likely to get potentially deadly superbugs, study reveals

  • Less than 10 per cent of those who think they have a penicillin allergy actually do
  • An allergy means people are more likely to be given generic antibiotics 
  • These can destroy good bacteria in the gut, raising the risk of serious infection

People diagnosed with penicillin allergies are far more likely to get superbugs after being prescribed antibiotics.

Around one in ten British people claim to be allergic to penicillin, but fewer than 10 per cent of them actually are, as doctors misdiagnose rashes and headaches in children as reactions to the drug.

A study of more than 300,000 people has now raised fears over the number of people wrongly diagnosed.

It found those who believe they have a penicillin allergy have a two-thirds higher risk of getting MRSA, which can cause blood stream infections and pneumonia.

They also have a quarter higher risk of Clostridium difficile, which causes extreme diarrhoea and fever.

Experts blame this on many people wrongly labelled as allergic to penicillin getting less targeted drugs from their GP for minor ailments like ear and throat infections. 

Experts worry people who are thought to have a penicillin allergy are given more general drugs, which destroy good bacteria in the gut and raise the risk of illness from ‘superbugs’

These ‘broad-spectrum’ antibiotics allow bacteria to evolve into superbugs which can be deadly in the vulnerable and elderly.

Dr Kimberly Blumenthal, from Massachusetts General Hospital in Boston, who led the study, said: ‘We found there are real harms to patients that result from a misdiagnosis of a penicillin allergy.

‘This warrants patient awareness, and also parent awareness because penicillin allergy is often diagnosed in childhood. 

‘Patients with a penicillin allergy label should reevaluate the diagnosis with their doctor and consider whether allergy testing should be pursued.’

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While children may show signs of being allergic to penicillin, this can often be a simple skin reaction caused by a virus. 

Even those with a positive diagnosis may no longer be allergic to penicillin a decade later, as their immune system ‘forgets’ its reaction to the drug.

Knowing more than 90 per cent of people in the UK who claimed to have an allergy to penicillin were wrong, the US researchers wanted to see the risk of their risk of contracting a superbug.

The study, published in the British Medical Journal, followed 301,399 people prescribed antibiotics by their GP, including 64,141 with a documented penicillin allergy, for six years.

Those with an allergy 69 per cent more likely to get MRSA 


Superbugs are usually formerly easy-to-treat infections which have become increasingly dangerous because of a rise in antibiotic resistance – a phenomenon in which overuse of antibiotics has caused bacteria and fungi to evolve to become immune to traditional treatments.

The World Health Organization has warned if nothing is done the world is headed for a ‘post-antibiotic’ era.

It claimed common infections, such as chlamydia, will become killers without immediate answers to the growing crisis.

Bacteria can become drug resistant when people take incorrect doses of antibiotics, or they are given out unnecessarily.  

Figures estimate that superbugs will kill ten million people each year by 2050, with patients succumbing to once harmless bugs.

Around 700,000 people already die yearly due to drug-resistant infections including tuberculosis (TB), HIV and malaria across the world.  

In addition to existing drugs becoming less effective, there have only been one or two new antibiotics developed in the last 30 years.

In September, the World Health Organisation warned antibiotics are ‘running out’ as a report found a ‘serious lack’ of new drugs in the development pipeline.

Without antibiotics, caesarean sections, cancer treatments and hip replacements would also become incredibly ‘risky’, it was said at the time. 

Those labelled with a penicillin allergy were 69 per cent more likely to get MRSA, the study found, and had a 35 per cent higher risk of Clostridium difficile, known as C. diff.

These people were four times more likely to be prescribed two particular types of broad-spectrum antibiotics, which are less targeted than penicillin, so may destroy larger numbers of vital gut bacteria. 

This bacteria is needed to keep C.diff, which occurs harmlessly in the gut, in check so it cannot cause illness.

It is less clear why they lead to MRSA, although this may be due to the drugs killing bacteria in a way which better allows them to evolve.

The results show higher use of broad spectrum antibiotics accounted for more than half of the increased MRSA risk and 35 per cent of the increased C.diff risk.

People should be tested more thoroughly 

The authors conclude that people should be given skin tests, and tiny amounts of penicillin to check they are really allergic so they can be safely treated with the drug if not.

Peter Gibson, spokesman for Antibiotic Research UK, said: ‘We urge medics to follow national guidelines set down by NICE in respect of diagnosing Beta-lactam antibiotics allergies.

‘That advice includes involving a specialist drug allergy service.

‘Patients should also see their GP if they suspect they have such an allergy – and there is information available via NHS Choices and other reputable sources on the signs of such an allergy.’

Non-specific antibiotics increase the risk of antibiotic resistance 

Professor Kamila Hawthorne, vice chair of the Royal College of GPs, said: ‘Diagnosing a penicillin allergy in childhood is often anecdotal, although occasionally it is very obvious when a patient has an anaphylactic reaction (for example, severe swelling around the mouth and lips and breathing difficulties).

‘On other occasions a child may present with a rash that is assumed to be an allergic reaction, when it might be a viral infection.’ 

She added: ‘The main issue with not being able to prescribe penicillin to a patient is that the safe alternatives tend to be broad-spectrum antibiotics and will therefore non-specifically affect a number of bacteria.

‘This increases the risk of both antibiotic resistance and pathogenic bacteria and fungal infections moving into the space vacated by safer bacteria.’

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