The Difference Between Allergy and Intolerance

All your questions answered about Food Allergy and Intolerances. Written by Registered Baby and Child Dietitian, and Milk Allergy Specialist, Christina Hills.

Many parents use “allergy” and “intolerance” interchangeably- but they actually mean different things. Understanding the difference can help you get the right diagnosis and the right diet plan.

Allergy

A food allergy happens when the immune system responds to food proteins like those found in cow’s milk, egg or peanut 

Allergic reactions can be immediate (IgE-mediated)- causing hives, swelling, vomiting or breathing difficulties — or delayed (non-IgE)- causing reflux, eczema or tummy issues.

Even a small amount of the food can cause a reaction.

Food Intolerance

A food intolerance does not involve the immune system. It happens when the body struggles to digest or process a food, often due to missing enzymes or a gut sensitivity.

Common examples include:

• Lactose intolerance- when the body can’t digest lactose, the sugar in milk.

• Fructose or sorbitol intolerance- in toddlers, sometimes causing bloating and loose stools.

Intolerances are usually dose-dependent- meaning small amounts may be tolerated and they don’t usually cause any dangerous reactions like those we see with severe allergy- like an anaphylaxis response to peanuts 

Both allergies and intolerances can cause distressing symptoms but the causes, diagnosis and management are very different. Understanding which applies to your child is key to finding peace and progress.

Need Extra Support?

If you’d like one-to-one guidance through an allergy diagnosis, reintroduction, or allergy-safe weaning, I offer personalised consultations to help you feel informed, and supported through every stage of your child’s allergy journey.

👉 Book a session or explore more resources in the Milk Allergy Hub.