Allergies to certain foods can be debilitating at best and potentially fatal at worst.
A new report from the Food Standards Agency says that around 30% of adults report experiencing adverse reactions when eating certain foods, but only around 6% of people – around 2.4 million people in the UK – have a clinically diagnosable allergy.
“Even if a food allergy seems mild, it could become life-threatening at any time,” says Dr Helen Evans-Howells, an NHS general practitioner (known online as Dr Helen Allergy), who has dedicated her career to allergy medicine since the birth of her son, who was allergic to milk as a baby and later developed an allergy to nuts. “For example, if you’ve ever gotten hives from eating sesame seeds, you could develop anaphylaxis the next time you eat them. Around 50% of deaths from anaphylaxis are in people who were told they had mild allergies.”
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What are food allergies?
A food allergy is an overreaction of the body’s immune system to proteins found in food.
Immunoglobulin E (IgE) is a specific immune cell that triggers a response. It’s part of the immune system designed to fight parasitic infections. Your body fights the parasites by coughing them up, sneezing, and producing tears to clear your eyes.
“If you have a peanut allergy, when you eat peanuts, IgE cells are formed which recognise its chemical composition,” says Dr Evans-Howells, director and chair of Anaphylaxis UK’s clinical science committee. “The IgE cells bind to the peanut and then attach to mast cells which contain all the chemicals such as histamine that control the allergic response. These chemicals are released and trigger a cascade of reactions.”
How do food allergies affect the body?
The most severe reaction is anaphylaxis (an extreme reaction of the immune system to food), which can rarely be fatal.
Signs of anaphylaxis include:
- The airways become narrow
- cough
- Voice changes
- Swollen tongue
- Difficulty breathing
- Dizziness, paleness, collapse
During anaphylaxis, “histamine dilates blood vessels and lowers blood pressure,” says Professor Stephen Till, an allergist practicing at HCA Healthcare UK at The Shard, “and it constricts the airways in your lungs, making it harder to breathe.”
Dr Evans Howells said: “Anaphylaxis is unfortunately very common and its incidence has increased significantly, although fortunately the mortality rate has decreased slightly.”
Anaphylaxis can sometimes resolve spontaneously. [resolve itself without treatment]”The body produces adrenaline, which reverses the effects of histamine on blood vessels. But you can’t expect it to go away on its own.”
How can I treat food allergies?
People with severe allergies are prescribed an epinephrine auto-injector (commonly known as an EpiPen or JextPen), which allows them to inject themselves with adrenaline to help stop the allergic reaction. Be sure to ask for help if you get such a prescription.
“If you see any signs of anaphylaxis, you should use epinephrine as soon as possible,” Dr. Evans-Howells says. “If you have hives, just swelling without airway issues, or a one-off episode of vomiting, diarrhea, or runny nose, use an antihistamine to treat those symptoms,” she says.
“Antihistamines can’t stop anaphylaxis, they only stop the reaction, so it’s important to use adrenaline as soon as a more severe reaction occurs.”
What is the difference between an allergy and an intolerance?
Sometimes people confuse “allergy” with “intolerance.”
“An allergy is when a certain part of the immune system reacts to something it shouldn’t react to. An intolerance is something that causes symptoms but is not immune in nature,” says Professor Till. “Some people experience bloating, gas or diarrhoea when they drink milk. These are common symptoms of lactose intolerance, but are not a milk allergy – the body just can’t digest lactose well.”
Intolerance reactions are generally less serious than allergic reactions. “Allergies can cause a medical emergency; intolerances almost never do.”
At what age do food allergies develop?
Milk and egg allergies are common in infants but usually outgrow by age 3 or 4. Tree nut and peanut allergies can develop in children but tend to continue into adulthood. Fish and shellfish allergies can develop at any time.
“Children who have severe allergies in childhood tend to continue to have them into adulthood,” Prof Till explains.
If you were allergic to milk or eggs as a child and have avoided them ever since, it may be worth getting re-evaluated by an allergist, but “allergies to things like peanuts, tree nuts, sesame, fish and shellfish tend to persist into adulthood, so long as the initial diagnosis was accurate,” says Prof Till.
Is there a cure for food allergies?
There is currently no cure for food allergies, but treatments and new therapies are now widely available.
A £2.5m trial at the University of Southampton, funded by the Natasha Allergy Research Foundation, found that food immunotherapy can help increase the amount of allergen a person can ingest before an allergic reaction occurs, but it is not a cure.
Dr Evans Howells’ private allergy practice in Poole, Dorset, has become the first community clinic in the UK outside London to offer food immunotherapy, a treatment that involves giving people, mainly children, tiny amounts of foods they are allergic to in order to reduce their sensitivity to those foods.
“You give them a small amount of the allergenic substance (in this case nuts) every day for a few weeks, then gradually increase the amount,” says Evans-Howells. “You essentially allow the allergen to evade the immune system, increasing the amount they can ingest before it triggers an allergic reaction.”
Immunotherapy has been widely available in the US and Canada for a decade, but is relatively new in the UK. “It takes time because you need appointments every two weeks and then you have to monitor the patient closely – the appointments take four hours,” says Dr Evans-Howells.
The problem is that food immunotherapy currently only works in children. “There is some evidence that it works in adults, but the success rate is lower,” explains Dr Evans Howells. “The human immune system is less flexible than children’s, so studies in adults tend to be less meaningful and have more side effects.”
But while immunotherapy certainly works, Dr. Evans Howells warns that it shouldn’t be attempted at home. “With peanut immunotherapy, the starting dose is 0.5mg. For comparison, one peanut is 300mg,” he says. “That’s a very small amount. If done incorrectly, this therapy can be deadly. Some people try it, but the results can be disastrous. It’s not worth doing.”
Another trial looked at a drug called omalizumab, which appeared to reduce allergic reactions while patients were taking the drug, but the reactions returned when patients stopped taking it. However, several trials are underway to see whether omalizumab can be used in combination with food immunotherapy in adults and children.
The nine most common food allergies are:
