Being allergic to certain food can be debilitating at the best of times and deadly at the worst.
According to a new report from the Food Standards Agency, around 30 per cent of adults report having adverse reactions when eating some foods. However, only around six per cent (around 2.4 million people in the UK) were found to have a clinically diagnosable allergy.
“Even when food allergies seem mild, they can turn life-threatening at any moment,” says Dr Helen Evans-Howells, an NHS GP (known online as Dr Helen Allergy) who has devoted her career to allergy medicine since the birth of her son, who was allergic to milk as a baby and then developed a nut allergy. “Even if you’ve only ever had hives from eating sesame, for example, you could go into anaphylaxis the next time. Around 50 per cent of deaths from anaphylaxis are in people who’d been told their allergies were mild.”
What are food allergies?
A food allergy is an overreaction by the body’s immune system to proteins found in food.
Immunoglobulin-E (IgE) is the particular immune cell responsible for causing a reaction. It’s a part of the immune system designed to fight parasitic infections. The body fights parasites by vomiting them up, sneezing them out, or clearing the eyes by watering.
“If you’re allergic to peanuts then when you eat a peanut, an IgE cell is shaped to recognise its chemical composition,” says Dr Evans-Howells, who is trustee and chair of the clinical and scientific panel for Anaphylaxis UK. “It binds to that peanut then attaches to a mast cell which contains all the chemicals that control an allergic reaction, like histamine. These chemicals are released, creating a cascade of responses.”
How do food allergies affect the body?
The most severe response is anaphylaxis – an extreme reaction by the immune system to food – which can, in rare cases, lead to death.
The signs of anaphylaxis are:
- The airways becoming constricted
- Coughing
- Voice changes
- Tongue swelling
- Breathing difficulties
- Dizziness, paleness, collapse
During anaphylaxis, “histamine causes the blood vessels to dilate, lowering blood pressure,” says Professor Stephen Till, a consultant allergist with a practice at HCA Healthcare UK at The Shard. “It also causes bronchial tubes in the lungs to constrict, so it becomes more difficult to breathe.”
Dr Evans-Howells says: “Anaphylaxis is sadly very common and rates of it have risen hugely, but thankfully the rates of death have reduced slightly.”
“Anaphylaxis can be self-limiting [resolve itself without treatment]. The body produces adrenaline which reverses the effects of histamine on the blood vessels. But you can’t rely on it to naturally resolve itself.”
How should you treat food allergies?
People with severe allergies are given adrenaline auto-injectors (commonly known as Epi-Pens or Jext pens) which allow them to give themselves a shot of adrenaline which should help stop the allergic response. Help should always be sought if this is given.
“You should use adrenaline as soon as you see a sign of anaphylaxis,” says Dr Evans-Howells. “If it’s just hives, swelling without any airway issues, one spell of vomiting, diarrhoea or a runny nose, then use antihistamines to treat those symptoms,” she says.
“Antihistamines won’t stop anaphylaxis, they only stop the reactions which is why it’s vital to use the adrenaline as soon as you get more serious responses.”
What is the difference between an allergy and an intolerance?
People sometimes confuse ‘allergy’ with ‘intolerance’.
“An allergy involves a very specific part of your immune system reacting to something it shouldn’t react to. An intolerance is something which causes symptoms, but not of an immune nature,” says Professor Till. “Some people might feel bloated, have wind and diarrhoea when they drink milk – that’s a common manifestation of lactose intolerance, but it’s not a milk allergy. It’s that their body can’t digest lactose well.
Generally, intolerance reactions are less severe than allergic reactions. “Allergies can cause medical emergencies. That’s not often the case with intolerances.”
At what age can food allergies appear?
Milk and egg allergies are more common in infants but they usually grow out of them by three or four years old. Tree nut and peanut allergies can come on in children but tend to last into adulthood. Fish and shellfish allergies can start at any time.
“The children who are more allergic in childhood tend to be those whose allergies persist into adulthood,” explains Professor Till.
If you were allergic to milk or eggs as a child and have avoided them ever since, it may be worth visiting an allergy specialist for another diagnosis. However, “things like peanut, tree nut, sesame, fish and shellfish allergies – as long as the original diagnosis was accurately made – tend to stick around into adulthood,” says Professor Till.
Are there any cures for food allergies?
There are no current cures for food allergies. However, treatments and new therapies are becoming more widely available.
A £2.5 million trial at the University of Southampton, funded by the Natasha Allergy Research Foundation found that food immunotherapy works to help increase the amount of an allergen a person can consume before they have a reaction. But it isn’t a cure.
Dr Evans-Howells’ private allergy practice in Poole, Dorset, became the UK’s first community clinic, outside of London, to offer food immunotherapy, a process by which mostly children are given minuscule amounts of the food they’re allergic to in order to decrease their sensitivity to it.
“You give someone a tiny amount of the thing they’re allergic to – in this case nuts – every day for a number of weeks, then you gradually add a bit more,” says Dr Evans-Howells. “You’re basically trying to sneak that allergen past their immune system which builds up how much they can have before a reaction is triggered.”
Immunotherapy has been widely used in the US and Canada for a decade, but it is relatively new to the UK. “It’s time-consuming because fortnightly appointments are needed and you need to have good supervision of patients afterwards – it’s a four-hour appointment,” says Dr Evans-Howells.
The trouble is that food immunotherapy currently only seems to work in children. “There’s some evidence that it works in adults, but it’s less successful,” explains Dr Evans-Howells. “Our immune systems are less malleable than children’s so adult studies tend to have less significant results and more side-effects.”
However, while immunotherapy does work, Dr Evans-Howells cautions that it must not be attempted at home. “With peanut immunotherapy the first dose is 0.5mg – for context, one peanut is 300mg,” she says. “It’s a tiny, tiny amount. In the wrong hands, this therapy could kill someone. Some people do try it but they may have tragic consequences. It just isn’t worth it.”
Another trial looked at a drug called Omalizumab, which seemed to reduce allergic reactions for as long as the drug was being taken, but the reactions returned once patients stopped. However, some trials are ongoing to see whether Omalizumab could be combined with food immunotherapy for adults and children.
These are the nine most common food allergies: