You ate something, you felt awful, and you still can't say why. Maybe it was bloating, a rash, or a whole day of feeling flattened, after a food you've eaten for years. Why me? And why now?
Start with a number that should make you careful. In a survey of 40,443 American adults, 19.0% said they had a food allergy. Going by the symptoms they described, the figure that looked convincing was 10.8%. So more than four in ten of those who believed it probably had something else going on. The same survey has a stranger finding: of the adults with a convincing allergy, 48.0% had developed it as adults. This is not only a childhood problem.
So here are the reasons food allergies and sensitivities occur, starting with how an allergy begins: seven things that seem to push it along, and what the old advice got wrong.
Allergy or sensitivity?
A food allergy is an immune error. Your body takes a harmless protein for a threat, makes antibodies against it, and reacts the next time it turns up, usually fast, with itching, swelling or hives, and at worst a reaction that can kill. Unconventional Remedies for Chronic Allergies, linked below, has where the word comes from. Philipp Dettmer's explains the system that makes that mistake.
A sensitivity is a looser word for something slower: bloating or a headache, hours or days after the meal, with none of those antibodies involved. This article is mostly about the first one. Food Allergies, Sensitivities, and Intolerances, linked below, has the second.
A rough guide. A true allergy tends to come on fast, often with hives, swelling or trouble breathing, and a small amount can set it off. A slower problem tends to show up in your gut or your head, comes and goes, and often depends on how much you ate. The tick in reason 3 is the exception, because it strikes hours later. All of that is a clue, not a diagnosis.
Is it really rising?
Partly, yes. Food Allergy Research & Education, an American charity, puts the number at 33 million Americans. Among US children, reported food allergy went from 3.4% in 1997–1999 to 5.1% in 2009–2011, a rise of 50%. Peanut allergy in American children went from 0.4% to 1.4% between 1997 and 2008.
Some of that is noticing. Across the UK, hospital admissions for anaphylaxis, the severe reaction, from all causes rose by 615% between 1992 and 2012, while deaths from it stayed flat. The authors suggest that growing awareness may be part of it. But genes don't change that fast, so it makes sense to look at what changed around us. Theresa MacPhail's follows why our bodies have become so irritable.
1. Timing: we told parents to wait
For years, the advice in the UK, Australia and North America was to keep peanuts away from babies. Peanut allergy kept on rising anyway.
Then researchers compared Jewish schoolchildren in two countries, 5,171 in the UK and 5,615 in Israel. In the UK, 1.85% had a peanut allergy. In Israel, it was 0.17%, about a tenth as much. The obvious difference was that Israeli babies ate peanut earlier, more often and in larger amounts. Much of that peanut came as Bamba, a peanut puff. Few snacks have a better research record.
So they tested it. In a trial of 640 babies at high risk, because of severe eczema, an egg allergy or both, half were told to avoid peanut and half to eat it regularly, until the age of five. Among the 530 babies whose first skin test was negative, 13.7% of the avoiders ended up allergic, against 1.9% of the eaters. Among the 98 who already tested positive, it was 35.3% against 10.6%.
Read that again. The careful advice may have been part of the problem. Early exposure to other common allergens may also protect, though the evidence is strongest for peanut.
Three warnings. Those babies were tested first and watched closely, so if yours has severe eczema or an egg allergy, get them checked before you try this. This is about preventing an allergy, not a recommendation to eat peanuts. Whole nuts are also a choking risk for children under five, so anything given to a baby needs to be crushed, ground, or spread as a nut butter on food such as toast.
2. Your skin: the wrong way in
Here is the odd one. You may become allergic to a food through your skin.
In a study following 13,971 British preschool children, peanut allergy went with an oozing, crusted rash, at about five times the odds, and with creams containing peanut oil, at nearly seven times. That last figure rests on parents' memories and a small number of children, so take it as a clue. In Australia, babies with eczema had 11 times the risk of a peanut allergy by their first birthday, and nearly six times the risk of an egg allergy.
What's in the house may count too. In the homes of 133 British children with peanut allergy, the household got through a median of 18.8 g of peanut a week, against 6.9 g in the homes of 150 children with no allergy. The babies themselves weren't eating any more of it. The link was strongest for peanut butter, and those who also ate peanut early seemed to be protected.
Then there's the soap. Japanese women began turning up with wheat allergy after using a facial soap that contained hydrolysed wheat protein. In one study of 157 women with self-reported wheat allergy and 449 without, current use of that soap went with 2.6 times the odds. They had been washing their faces.
Put that next to the peanut trials and a working idea appears. A food first met through broken skin may be read as a threat, and a food first met through the gut is more likely to be accepted. It isn't settled, but it does explain why a baby's eczema and a baby's first foods keep turning up in the same studies.
3. The tick
This one a meat-first site has to tell you honestly. A tick bite can make you allergic to red meat.
A bite can leave you with antibodies to alpha-gal, a sugar found in mammals, including beef, pork, lamb, venison and rabbit, and in gelatin and milk. The lone star tick is the usual suspect in the US and the paralysis tick in Australia. Reactions typically begin 2 to 8 hours after eating, and they can be serious. In the first 24 patients described in detail, the hives or anaphylaxis came on 3 to 6 hours after the meal. Think how hard that is to trace. You won't blame a steak you ate that long ago.
The clue came from an unlikely place. Thomas Platts-Mills and his colleagues were trying to work out why some patients reacted badly to a cancer drug, cetuximab, and found antibodies to the alpha-gal in it. Then Platts-Mills was bitten by a tick himself and developed the allergy, and the team made the link. He didn't need to go that far to prove it.
Poultry and seafood don't contain it. The tick has nothing against a chicken. The allergy can improve if you avoid further bites, over anything from eight months to five years. The problem here is the tick and not the meat, but if you get hives a few hours after red meat and you've been bitten, ask for the test. Check yourself after walks through long grass, and take off any tick you find early, with fine-tipped tweezers such as this .
4. Too clean, too polluted
The original hygiene idea was that children meeting fewer microbes grow up with immune systems more likely to overreact. Unconventional Remedies for Chronic Allergies has the best evidence for it, Amish children who grow up beside farm animals, with allergies six times as rare as in a similar farming community. There is one food-specific clue as well. In a large Australian study of babies, having a pet dog went with less allergy across every group they looked at, including egg and peanut. That's a link, so don't buy a dog as treatment, but it fits. Your Hay Fever May Start on the Road, Not in the Field has the other side, the diesel particles that taught people's immune systems a new target.
Both of those are mostly about what you breathe, and the link to food allergy is less direct. But letting your children play outdoors and keeping them away from smoke and traffic both cost little.
5. Your gut
Processed food gets the blame here, and part of that is fair. Foods That Upset Your Gut: What's Real and What's Personal has what emulsifiers do to the protective layer of the gut, and why the barrier is real while "leaky gut" as a diagnosis is shakier.
How much of this starts a true allergy is still an open question. A damaged gut lining is a much better explanation for the slower reactions, and Food Allergies, Sensitivities, and Intolerances goes through them.
6. A bad night and a hard run
This one doesn't start an allergy, but it does change the day it bites you.
In a trial with 81 adults with peanut allergy, researchers measured how much peanut it took to set off a reaction. After exercise, that amount fell by 45%. After a night of sleep deprivation, it also fell by 45%. So a food you got away with on Monday may catch you after a short night on Thursday, and it can look as though the allergy is coming and going. It isn't. You just slept badly.
So if you know you have an allergy, be stricter after a short night or around hard exercise. That's the day to read the label twice.
Stress often gets added to this list, and it may well belong there, but this trial didn't test it.
7. Vitamin D: a lead, no more
Food reactions sent more Americans to emergency departments in the Northeast than in the South, with about a third higher odds, and the authors wonder about sunlight and vitamin D. But when Australian researchers measured vitamin D in babies, they found no link with food allergy at one year, mostly egg allergy in that group. So it's a question, not an answer. Your skin makes vitamin D in the sun and you want it for other reasons, but don't count on it here.
What the old advice got wrong
You'll read that an overburdened liver and a "sluggish" lymphatic system let toxins build up and set off food reactions. No good evidence for that turned up. Your liver clears what it can around the clock, and Hidden Toxins in Your Diet: What's Really in Your Healthy Food has what a cleanse does and doesn't do.
You'll also read that eating the same food again and again gives you an allergy to it. In the peanut trial, eating it regularly was what protected those children.
And you'll be told to eat a colourful variety of fruit and vegetables to prevent it. No good trial supports that either, and raw apple is one of the foods that can set off a birch pollen allergy.
What to do
Keep a food diary, and look three days back. Write down what you ate and how you felt. A same-day diary misses the slow reactions, as Food Allergies, Sensitivities, and Intolerances explains.
Test it properly. A positive skin or blood test doesn't always mean a real allergy. The check that counts is eating the food under supervision, which is called an oral food challenge. If you've ever had a severe reaction, don't try this at home.
Heat can change the answer. When 100 children with milk allergy were given heavily heated milk under supervision, 68 tolerated it, though not ordinary milk, and 9 tolerated both. The other 23 reacted, and more severely than the others had reacted to ordinary milk. So don't try this at home either.
Don't assume it's for life. Childhood allergies to milk, eggs and soy often go with age, while those to nuts and shellfish typically stay. So an allergy from childhood is worth checking again.
Skip the online panels. Hidden Toxins in Your Diet has what those blood tests measure, which is how your body responds to your regular meals. So the test may simply have read you your shopping list.
Don't cut foods on a guess. With a child this matters most, because a wrong diagnosis of milk allergy can lead to poor growth and missing nutrients, as well as real reactions if the true cause is missed. Take out one food, check the result, and put it back if nothing changes.
Start from something simple. Meat, fish and eggs make a plain base for finding out what you react to, with one food added back at a time. Be honest about this, though, because they aren't all innocent. In that survey of American adults, shellfish was the most common allergy at 2.9%, with milk at 1.9% and fin fish at 0.9%. If one of those is your suspect, take it out as well.
Read the label every time. In the US, milk, egg, peanuts, tree nuts, fish, shellfish, soy, wheat and sesame must be named on the label. "May contain" warns of traces picked up in the factory. Other countries list different foods, so check when you travel.
Wash with soap. After handling peanut, liquid soap, bar soap or wipes left none detectable on hands. Plain water left it on 3 of 12 hands and antibacterial sanitiser on 6 of 12. Ordinary household cleaners cleared it from tables, except dishwashing liquid, which left it on 4 of 12.
Look after a baby's skin. Treat eczema early, and read the label on creams and soaps for food oils and food proteins.
Tell the people who kiss you. Right after a peanut meal, saliva can hold enough allergen to set off a reaction. In most of those tested it was gone within an hour with no effort at all, and none had it several hours later after a peanut-free lunch. Brushing and rinsing cut it, but it was still detectable in about 40% of samples.
Have a plan for a bad day. Swelling in the throat, trouble breathing or fainting means calling the emergency services straight away, and using adrenaline if you've been prescribed it. Tell the school, the people you live with and anyone you eat with what to do, and consider wearing a medical alert bracelet.
So, why you?
There may not be one answer. It could be what you met first and how you met it, the state of your skin, a tick you've forgotten, or a bad night that lowered the bar. Most of that is outside your control now. What's left to you is to stop guessing, and find out which one you're dealing with.
Look at your daily habits, then. Tonight, write down what you ate today and how you felt, and keep it up for the next three days.
Reacting to meals, but no allergy shows up? Food Allergies, Sensitivities, and Intolerances: Why Your Body Keeps Reacting to Food That's Supposed to Be Good for You — the three kinds of reaction, the gut barrier, the tests that miss them, and elimination diets.
Allergies in your nose and eyes as well? Unconventional Remedies for Chronic Allergies — where the word comes from, the Amish children, the bedroom, rinsing, and what the evidence doesn't support.
Know someone convinced they're allergic to half the kitchen? Send them this, and ask when they were last tested.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. A severe allergic reaction is an emergency, so call the emergency services straight away.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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