What is a food allergy?
The US national guidelines for food allergy give a consensus definition. They cover two kinds of reaction. Some are driven by IgE, the antibody behind most quick allergic reactions. Others are not (called non-IgE-mediated).E2Good1
In a large German study that confirmed reactions with blinded food challenges, about 3.6% of people had a real adverse reaction to food. Of these, 2.5% were IgE-mediated and 1.1% were not.E2Good9
The same study found that about 35% of people said they had reacted to a food at some point in life. That is far more than the challenges confirmed.E2Good9
How common is food allergy in adults?
A national US survey estimated that 10.8% of adults, more than 26 million people, have a convincing food allergy. Nearly 19% of adults believe they have one.E2Good2
The most common adult food allergies in that survey were shellfish (2.9%), milk (1.9%), peanut (1.8%), tree nuts (1.2%) and fin fish (0.9%).E2Good2
The authors concluded that adults with a suspected food allergy need proper confirmatory testing and counseling. The aim is that foods are not avoided for no reason and quality of life is not harmed.E2Good2
What else can look like a food allergy?
The US guidelines note that people often confuse reactions that are not allergic, such as food intolerance, with food allergy. This makes the public believe food allergy is more common than it is.E2Good1
- Lactose malabsorption. Around two thirds of the world's adults do not fully absorb lactose, the sugar in milk, with wide differences between regions.E1Strong3
- Celiac disease. An immune reaction to gluten that affects about 1% of people in most populations. It ranges from severe malabsorption to almost no symptoms.Review10
- Scombroid poisoning. Spoiled fish such as tuna and mackerel can carry large amounts of histamine. Flushing and headache began 10 to 30 minutes after eating the fish in the study that identified histamine as the cause.E2Good4
- Hives. Hives are common: about 1 in 5 people has acute hives at some point in life.E2Good11
Because so many things can look alike, the German study concluded that a step-by-step approach that includes food challenges is needed to confirm the diagnosis.E2Good9
Do children outgrow food allergies?
Some do, and it depends on the food. In one large clinic group, milk allergy had resolved in 19% of children by age 4 and 42% by age 8. It had resolved in 64% by age 12 and 79% by age 16.E2Good5
In a similar study, egg allergy resolved in 4% by age 4 and 12% by age 6. It resolved in 37% by age 10 and 68% by age 16. Most children with egg allergy are likely to outgrow it by late childhood.E2Good6
Peanut allergy was long thought to be rarely outgrown. One study found it was outgrown in about 21.5% of patients. A population study in Australia found it resolved in 22% of children by age 4.E2Good7,12
About 9% of people with tree nut allergy outgrow it, including some who had severe reactions before.E2Good8
Many children with milk or egg allergy can eat these foods when they are extensively heated, as in baked goods. About 75% with milk allergy tolerated heated milk in one study. Most with egg allergy tolerated heated egg in another.E2Good13,14
European guidelines describe checking children with food allergy again over time, with allergy tests or supervised food challenges. The aim is that a food can return to the diet if tolerance has developed.E2Good15
How is food allergy managed?
After an IgE-mediated food allergy is confirmed, European guidelines name several essentials. These are avoiding the allergen with dietary advice (ideally from a specialized dietitian) and a written treatment plan. They also cover education on recognizing symptoms and a prescription for medicines including an epinephrine auto-injector.E2Good16
Treatments that change the allergy itself, such as oral immunotherapy and omalizumab, have their own guide: Immunotherapy for allergies.
What is not known yet
The milk allergy study found the outlook was worse than earlier reports had suggested. Still, some patients outgrew it in their teens, which is why follow-up matters.E2Good5
For tree nuts, researchers could not firmly recommend test cut-offs for deciding when a supervised challenge makes sense.E2Good8
Questions you might bring to your clinician
- Was this an IgE-mediated allergy, a non-IgE reaction, or something else such as an intolerance?
- Which tests, if any, would help confirm it, and what can each test show and not show?
- Is a supervised food challenge worth considering, now or later?
- If this is a child's allergy, how often should it be checked again?
- Is there a written emergency plan, and who should have a copy?