Since childhood, Charlotte Campbell has felt unwell after eating peanuts, but it was only after a scary incident at a wedding aged 21 that she was diagnosed with a peanut allergy.
‘After eating a fried risotto ball at the reception I started getting a very itchy mouth, blocked sinuses and hives – then, within 30 minutes, it developed into nausea and vomiting,’ recalls Charlotte, a marketing manager who lives with her husband Will, 33, a teacher, in Hitchin, Hertfordshire.
‘I’d never experienced anything like it,’ she says.
‘As a child, I occasionally ate peanut butter or the odd thing containing peanuts, which made me feel sick and gave me a slightly itchy mouth. But I never suspected an allergy.’
Thankfully her sister, who had a diagnosed nut allergy, was also at the wedding and gave Charlotte antihistamines, which worked quickly.
A few weeks later Charlotte was referred for skin-prick tests, where a tiny amount of an allergen is placed on the skin, to look for any reaction.
Charlotte was tested for all common food allergies. When her arm became red and the skin raised in response to peanut, only improving after a couple of days, the diagnosis was confirmed.
Around 6 per cent of the UK adult population – around 2.4 million people – have a confirmed food allergy. In general, they are just told to avoid eating what they’re allergic to; there is no treatment.
Since childhood, marketing manager Charlotte Campbell, 32, has felt unwell after eating peanuts – but it was only due to a scary incident at a wedding aged 21 that she was diagnosed with an allergy
‘It made me anxious around food, especially when eating at other people’s houses and at restaurants,’ says Charlotte, now 32.
‘I had a couple of incidents when I ate things I thought were safe, such as a flapjack, and I quickly developed symptoms which eased off with antihistamines.’
Yet Charlotte can now safely eat a small amount of peanuts thanks to a groundbreaking clinical trial, using an approach known as oral immunotherapy.
This is where patients are gradually given tiny but increasing amounts of the food they’re allergic to, in a safe environment with medics on hand, in a bid to train their bodies not to react.
While an oral immunotherapy treatment has been approved for children, there isn’t an equivalent available for adults because of a concern that their immune systems are less adaptable than children’s. They also tend to have more severe reactions (it’s not clear why).
But now, for the first time, this method has been shown to be effective in adults.
In a study, led by King’s College London and Guy’s and St Thomas’ NHS Foundation Trust, participants received a tiny dose of peanut in hospital and were monitored for a reaction, before being sent home and instructed to take that same peanut dose daily for two weeks. The process was then repeated, increasing the dose in small increments, over around four months.
The study found that 67 per cent of the 21 participants were able to consume at least 1.4g peanut protein – the equivalent of five peanuts – after a minimum of four months without reacting, reported the journal Allergy in April. ‘If you can repeatedly expose the allergic patient to the things they’re allergic to, you can desensitise them and eventually make them less reactive,’ explains Professor Stephen Till, a consultant allergist at Guy’s and St Thomas’ and chief investigator of the trial, which was funded by the National Institute for Health and Care Research.
‘The challenge is giving someone something they’re allergic to without causing a reaction, which is why we do this in a controlled medical environment.’
When someone consumes a substance to which they’re allergic, their immune system produces immunoglobulin E (IgE) antibodies. These attach to the allergen, and activate immune cells to attack it, triggering the release of histamine. Histamine causes symptoms such as itching, swelling, redness, difficulty breathing, sickness, diarrhoea and low blood pressure.
Some 6 per cent of the UK adult population – or about 2.4 million people – have a confirmed food allergy, with peanuts ranking as one of the most common
But oral immunotherapy is thought to make the body produce a different antibody, immunoglobulin G (IgG).
‘We think IgG soaks up the allergen and stops it binding to IgE,’ explains Professor Till.
After the treatment is over and desensitisation is established, patients are advised to stick to having their safe number of peanuts each day to maintain the benefits.
‘We’ve shown that desensitisation works, and that patients will remain desensitised if they carry on eating peanuts every day – but we need more studies to know if they would continue to be desensitised if they stopped,’ says Professor Till.
‘Before this, all adults with an allergy could do was be very careful to avoid peanuts.
‘Now there’s hope that there could be a treatment to control the way that the immune system responds. Participants don’t need to worry if there is cross-contamination in their food from peanuts in a restaurant, for example.’
However, oral immunotherapy is time-intensive, which makes NHS provision and funding difficult. For this reason, ‘it’s important that we work out how to deliver immunotherapy predominantly at home or outside hospitals’, says Professor Till.
Another new tool is with treatments known as biologics, such as omalizumab, which stop IgE antibodies binding to immune cells. These could be used alongside oral immunotherapy and help people to tolerate higher doses of their allergen more quickly, explains Professor Till.
Other experts believe biologic drugs could be a standalone food-allergy treatment. In a US study published in the New England Journal of Medicine last year, children under 18 with peanut allergy were given injections of omalizumab or a placebo every two to four weeks for 16 weeks. At the end of the trial 67 per cent of participants who’d received omalizumab could tolerate 600mg of peanut protein, compared with 7 per cent in the placebo group.
‘While this is an important study, if you’re mopping up the IgE, you’d expect 100 per cent efficacy,’ says Mohamed Shamji, a professor in immunology and allergy at Imperial College London. ‘We’re trying to find out why it doesn’t work for everyone.’
Even so, he believes the drugs should be considered for food allergies; currently they’re not approved for this on the NHS (partly because they are expensive), though they are in the US.
Another promising development is using virus-like particles (VLPs) to essentially create a peanut allergy vaccine. VLPs are designed to look like a virus, so activate the immune response, but do not cause illness.
Researchers at Imperial College London attached a VLP to peanut allergen protein Ara h2, to help the immune system recognise and respond to the peanut allergen in a controlled way.
Professor Stephen Till, a consultant allergist at Guy’s and St Thomas’ NHS Foundation Trust, says patients can be desensitised to their allergies by repeated exposure
An early-stage clinical trial, published in the Journal of Allergy and Clinical Immunology in January this year, found the vaccine caused no adverse reactions. Further trials are planned.
‘The aim of the vaccine is to reset the immune response, so it becomes more of a healthy, non-allergic one,’ explains Professor Shamji, a senior author of the study.
There is a great need for new treatments, says Clare Mills, a professor of food and molecular immunology at the University of Surrey: ‘If someone is allergic to peanut, then just a few milligrams of it, equivalent to a speck of dust, can provoke a potentially fatal reaction.’
Meanwhile, the Natasha Allergy Research Foundation, the UK’s food allergy charity, is funding an oral immunotherapy trial using everyday, shop-bought foods as a treatment for young people aged three to 23 with peanut and cow’s milk allergies, across nine NHS centres in England and Scotland.
As Tanya Ednan-Laperouse, the charity’s founder, explains: ‘We know that some individuals on the trial have had a very positive response. We hope our findings [due next year] will show oral immunotherapy using everyday foods is not only effective but cost-effective, and will lead to it being adopted as a treatment for food allergies on the NHS.’
A year after the 2019 trial Charlotte took part in, she was able to eat up to four peanuts a day.
But after a bad reaction last summer has dropped down to three, though hopes to go back to four soon.
‘It’s made me a lot less fearful of foods, especially when eating out,’ says Charlotte. ‘Everything feels much easier now.’