Food allergy vs. food intolerance: What is the difference and can I prevent them?
What is an allergy?
An allergy happens when a person’s immune system treats a substance (allergen) like an inappropriate invader. The body will try to protect itself by releasing a chemical into the body called histamine. This chemical is what causes the symptoms that are unpleasant or even dangerous. The reaction can start very suddenly, even after being exposed to a small amount of the allergen.
Allergens can get into the body in different ways. They can be:
- inhaled (such as dust or pollen),
- ingested as food (some common ones are nuts, eggs or shellfish),
- ingested as medication (such as penicillin),
- injected by an insect sting (like a bee or wasp venom), or
- absorbed through the skin (such as poison ivy).
What foods are common allergens?
Any food can trigger an allergic reaction, but the most common are:
- tree nuts
Are there any foods I should avoid while breastfeeding to prevent my child from getting allergies?
You don’t need to avoid milk, egg, peanut or other foods while breastfeeding. There is no evidence that avoiding certain foods will prevent allergy in your child.
Is there a particular formula I should use to prevent allergies?
If breastfeeding is not an option or if you choose not to breastfeed, use a store-bought iron-fortified infant formula for the first 9 to 12 months. The formula should be cow’s milk-based. There is no evidence that soy-based or hydrolyzed formula will prevent your child from developing an allergy.
Should I wait to offer common food allergens to my baby for the first time?
- Don't delay. In infants at low risk for food allergy, common food allergens can also be introduced at around 6 months of age to try to prevent an allergy.
- For children considered at high risk of developing an allergy (e.g., they have a parent or sibling with an allergic condition, or they have other allergies, such as eczema), consider introducing common food allergens at around 6 months of age, but not before 4 months.
- When introducing foods that are common food allergens, try offering no more than 1 per day. Wait 2 days before you introduce another. This makes it easier to identify a food that may have caused a reaction.
- Once you offer these foods to your child, it’s important to continue to offer them on a regular basis.
- If you have concerns, speak to your health care provider.
How will I know if my child has a food allergy?
Most often, your child will have to eat a food more than once before you know they are allergic. For example, the first time your child is exposed to nuts, there will probably be no reaction. If they develop an allergy to nuts, the next exposure could be more serious.
What are the signs of an allergic reaction to food?
An allergic reaction can affect many different body parts. Symptoms can include:
- itchy mouth and throat when eating certain foods,
- hives (raised red, itchy bumps on the skin),
- stomach trouble (diarrhea, cramps, nausea, vomiting),
- swelling of the face or tongue, or
- trouble breathing.
What is anaphylaxis?
Allergic reactions can be very serious, even life-threatening. In rare cases, a child may have a rapid and severe reaction to an allergen. This is called anaphylactic shock or anaphylaxis. It can happen within minutes or up to 2 hours after being exposed to an allergen.
What are the symptoms of anaphylaxis?
A severe allergic reaction can cause:
- difficulty breathing,
- swelling of the face, throat, lips, and tongue (in cases of food allergies),
- rapid drop in blood pressure,
- tightness of the throat,
- hoarse voice,
If any of these happen to your child, go the nearest emergency department or call 911 immediately.
Do children outgrow food allergies?
Many children outgrow food allergies, especially if the allergy started before age 3. Allergies to milk, for example, will usually go away. However, some allergies, like those to nuts and fish, probably won’t go away.
What is food intolerance?
Food intolerance is different from an allergy. It is not caused by an immune reaction. Food intolerance will cause discomfort, but it’s not dangerous to your child.
How can I tell if my child has food intolerance?
Your child may experience bloating, loose stools, gas or other symptoms after eating a specific food. Even though this reaction is not dangerous, if it causes your child discomfort you might want to avoid those foods in the future.
What is lactose intolerance?
Lactose intolerance happens when the body doesn’t produce enough of the enzyme lactase to fully break down the sugar (lactose) found in most dairy products. It is rare in young children and usually only develops after 3 years of age. While some young children adjust to the lack of this enzyme, some will have problems for life.
If your child is lactose intolerant, you can give them the calcium they need by offering lactose-free or lactose-reduced milk.
While none of these items will provide enough calcium on their own, it’s also healthy to offer:
- fortified soy milk,
- canned salmon and sardines with edible bones,
- oranges or fortified orange juice,
- almonds, and
- pinto beans.
Many of these foods do not provide enough vitamin D. Talk to your doctor about whether a supplement of vitamin D would be right for your child.
When should I call the doctor?
It is hard to diagnose food allergies. If your child has a reaction to a food, you will need to see your doctor. Your doctor will refer you to an allergist for the right testing.
If a serious allergy is confirmed, your doctor may prescribe a medication (e.g. EpiPen or Allerject), a needle that will protect your child right away if they are exposed to the allergen.
More information from the CPS
- Newly Diagnosed Support Centre (Food Allergy Canada)
- Living Confidently with Food Allergy Handbook: A Guide for Parents and Families (Food Allergy Canada)
- Food allergies and babies (UnlockFood.ca, Dietitians of Canada)
- Food allergies and intolerances (UnlockFood.ca, Dietitians of Canada)
Reviewed by the following CPS committees
- Allergy Section
- Community Paediatrics Committee
- Nutrition and Gastroenterology Committee
Last updated: March 2021