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Millions Mistakenly Think They Are Allergic to Penicillin

On the 95th anniversary of the discovery that penicillin could kill many of the common bacteria that infect people, experts have warned that many of us mistakenly think we are allergic to penicillin.

Around 6% of people in the UK have a penicillin allergy label on their medical record, equating to an estimated four million people, explained the Royal Pharmaceutical Society (RPS). However, over 90% of patients were found not to have an allergy to it when fully assessed, the Society pointed out. It said that being labelled allergic to penicillin was associated with a "higher mortality rate" of an extra six deaths per 1000 patients in the year following treatment for infection.

"Millions of people are potentially missing out on the best antibiotic if they develop an infection because they mistakenly believe they are allergic to penicillin," alerted the RPS. This meant their health could be "compromised" by receiving different antibiotics that may be "less effective, prolong recovery periods, and could cause admission to hospital", it warned.

It was in 1928  when Dr Alexander Fleming, a Scottish bacteriologist working at St Mary's Hospital in London, returned from holiday to find mould growing on a Petri dish of Staphylococcus bacteria. Having noticed that the mould appeared to prevent bacteria around it from growing, he soon identified that the mould produced a self-defence chemical that could kill bacteria. He named the substance penicillin.

Penicillin Allergy Day began in the US and is celebrated on 28 September. It is being marked for the first time by the RPS with a focus on the impact a penicillin allergy label has and how it can affect a patient's treatment.

Risk of Genuine Penicillin Allergy Low

"Many individuals are at low, or very low risk, of having a genuine penicillin allergy," said Tase Oputu from the RPS. "We often find that after careful investigation that they can take penicillin safely," she highlighted. She emphasised that those who may have had a severe reaction in the past would need allergy testing, and in some cases "may never" be able to take penicillin. 

People might believe they are allergic to penicillin for a variety of reasons, underlined the RPS. Some of these reasons included:

  • Common side effects of antibiotics, such as nausea or diarrhoea, were often confused with allergic reactions
  • Symptoms of the infection being treated, for example a rash, could be considered an allergic reaction and reported as such
  • Allergy reported years ago, perhaps in childhood, had settled down but the perception of an allergy remained

"Once on a patient's record, a penicillin allergy label can remain there for years without question, compromising their treatment," the RPS stressed.

Amena Warner, head of clinical services for Allergy UK, explained that many people were labelled for penicillin allergy from early childhood, often after having a rash with antibiotics. "This label can be carried with them the rest of their lives, without it ever being investigated," she pointed out. 

Penicillin Allergy Label Removal Possible

Although there are long waiting times to see a specialist allergist for a definitive test, the RPS believed that there were other ways to remove a penicillin-allergy label. There was now a national effort looking into this and the best way to do it, Ms Warner reassured. Compiling a detailed history of symptoms is the main method. This can be given to a healthcare specialist as part of a consultation," explained the RPS.

The RPS and its Antimicrobial Expert Advisory Group called on patients to check their medical record the next time they visited their GP, to ensure they were not wrongly labelled as allergic to penicillin. 

Ms Oputu emphasised that every medicine had benefits and harms and urged patients to "ask questions about a penicillin allergy label on their medical record".

"Patients should talk to their pharmacist or other health professional to help understand the difference between side effects and allergic reactions, which can sometimes look similar, so they receive the most effective treatment for their needs," she advised.

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