What is the difference between a milk allergy and lactose intolerance?

Milk allergy and lactose intolerance are common reactions to dairy milk. Milk allergy affects more than 1 in 50 young children in Australia and New Zealand.

Milk allergy is a problem with your immune system. This causes your body to react to the protein in milk. An allergy usually causes symptoms in your stomach as well as in other parts of your body.

Lactose intolerance is a problem with your digestive system. It means your child doesn't have the enzyme needed to digest lactose. Lactose is the sugar that is found in milk.

There are some common symptoms between both milk allergy and lactose intolerance in children. Many young children grow out of their milk allergy or lactose intolerance.

Don’t remove milk or dairy products from your child’s diet unless told by your doctor.

What are the symptoms of milk allergy and lactose intolerance?

Milk allergy

Allergic reactions to milk can take minutes to several hours to happen.

Rapid reactions may take up to 2 hours to appear and include:

• hives (urticaria — a red, itchy skin rash)
• tingling and swelling of the lips, face or eyes
• difficulty breathing
• stomach pain
• nausea, vomiting or diarrhoea
• change in consciousness or floppiness in babies or young children

Delayed reactions include:

• an increase in skin rash, such as eczema
• nausea, vomiting or diarrhoea
• stomach pain and bloating

If you start to see an unusually large amount of mucus, and sometimes streaks of blood, in your baby’s poo, it could be a sign of a food intolerance or allergy.

Lactose intolerance

The symptoms of lactose intolerance in babies and children are:

• being irritable
• stomach aches
• bloating
• passing a lot of gas
• liquid, frothy stools (poo), which may also be green
• nappy rash
• slow weight gain

These symptoms can be common in babies. They don't necessarily mean your child has lactose intolerance. But if your child has ongoing diarrhoea or is not putting on weight, see your doctor.

What causes milk allergy or lactose intolerance

Milk allergy

Milk allergy occurs when your child's immune system reacts to the protein in milk. It’s one of the most common food allergies in young children. Most children outgrow milk allergy by the time they reach school age.

Lactose intolerance

Lactose is the sugar found in the milk produced by mammals, including humans. Some people don’t produce enough lactase to break down the lactose. Lactase is an enzyme that helps you to digest lactose.

Very few babies have true lactose intolerance. This is a rare genetic condition where you have no lactase enzymes at all. This is called primary lactose intolerance.

Babies and young children can become temporarily intolerant to milk. This happens when the lining of their gut is damaged. It can happen if they have gastroenteritis, or an allergy or intolerance to another food. It will get better once the gut heals. This usually takes a few months. This is called secondary lactose intolerance.

Lactose intolerance is more common among:

• Aboriginal and/or Torres Strait Islander people
• people from Asia and Africa
• people from the Middle East
• people from some Mediterranean countries

When should my child see a doctor?

It’s very important to see a doctor if your child has symptoms of milk allergy.

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How is milk allergy or lactose intolerance diagnosed?

Your doctor will ask about your child’s symptoms and do medical tests, such as a:

• skin test
• blood test
• stool (poo) test
• breath test

Tests that aren’t supported by evidence do not have a place in testing for milk allergy. Avoid tests like:

• vega testing
• kinesiology
• ALCAT tests

If your doctor thinks that your child is lactose intolerant, they may suggest cutting out lactose from your child’s diet.

How are milk allergy and lactose intolerance treated?

Treatment for milk allergy

If your child is allergic to milk, you need to completely remove dairy products from their diet. You may also need to avoid milk from other animals, such as goats.

You will also need to remove other foods that contain milk. This may include solid foods such as cakes, biscuits and other packaged foods.

You will need to follow your doctor's advice and read food labels carefully. Watch out for other words used to describe milk on food labels, such as:

• butter and ghee
• buttermilk and cream
• casein and caseinates
• cheese and curd
• dairy
• milk solids
• yoghurt and whey

You should also use coconut products with caution. These may be contaminated with cow’s milk.

If your child is over the age of one, they can be given soy milk, or other calcium-enriched milks made from:

• nuts
• oat
• rice

It’s important to make sure your child is getting enough calcium.

Do not reintroduce milk or dairy products into your child’s diet until your doctor says it’s safe.

Medicines for milk allergy

If your child is allergic to milk, you may be advised to carry an adrenaline autoinjector (EpiPen® and Anapen®).

Severe allergic reactions can sometimes lead to anaphylaxis. This is an emergency and can even be fatal (cause death). You can use an adrenaline autoinjector to give first aid in the event of anaphylaxis.

Can I still breastfeed my baby who has a milk allergy?

Breastmilk is best, including for babies who have a milk allergy. In some cases, your doctor may advise you to remove milk and dairy products from your own diet.

In other cases, you may be able to eat your regular diet. You can speak to your doctor for guidance.

Which formula can I use for my baby who has a milk allergy?

If your baby is formula-fed, and they have a milk allergy then you can use extensively hydrolysed formula (EHF) or amino acid-based formula (AAF).

Do not use formula made from:

• cow's milk
• goat's milk
• sheep's milk
• hypoallergenic (HA) or A2 milk
• lactose-free formulas

If your baby is over 6 months old, and not allergic to soy, you can also use soy protein formula.

Treatment for lactose intolerance

The main treatment for lactose intolerance is to reduce or remove lactose in your child’s diet.

Older children will need to cut down on, but not eliminate, dairy foods from their diet. They can still have some:

• cheeses
• yogurt
• calcium-fortified soy products
• lactose-free milk, butter and cream

Your doctor or a dietitian will advise you on the best diet for your child.

Most of the time, young children will recover from lactose intolerance after a few weeks on a low-lactose diet.

Speak to your doctor or dietitian about how to slowly reintroduce milk and dairy products into your child’s diet.

Can I still breastfeed my baby if they are lactose intolerant?

If your baby is lactose intolerant, you should keep breastfeeding.

Reducing the amount of dairy in your diet will not reduce the amount of lactose in your breastmilk.

Which formula can I use for my baby who is lactose intolerant?

If your baby is formula-fed, talk to your doctor or child health nurse before switching to a low-lactose or lactose-free formula.

Resources and support

For support to deal with milk allergy and lactose intolerance, you can get help from:

• your doctor
• your child health nurse
• Australasian Society of Clinical Immunology and Allergy
• Australian Breastfeeding Association on 1800 686 268

Read more about avoiding food allergies in babies from the Royal Australian College of General Practitioners.