Lactose Intolerance

Frequently Asked Questions

This document has been developed by ASCIA, the peak professional body of clinical immunology/allergy specialists in Australia and New Zealand. ASCIA information is based on published literature and expert review, is not influenced by commercial organisations and is not intended to replace medical advice.

For patient or carer support contact Allergy & Anaphylaxis Australia or Allergy New Zealand.

ASCIA PC Lactose Intolerance FAQ 2024140.52 KB

Q 1: What is lactose?

Lactose is a naturally occurring sugar that is found in dairy foods such as cow’s milk, yoghurt and cheese. Lactose is also the main sugar in human breastmilk. To be absorbed by the body, lactose needs to be broken down by an enzyme called lactase into galactose and glucose, which are simple sugars. This happens in the small intestine which is part of the digestive system (the gut).

Q 2: What is lactose intolerance?

Lactose intolerance happens when the body doesn’t produce enough, or any, lactase enzyme to break down all the lactose in dairy products. For some people, this is long term and for others, it is short term:

Primary lactose intolerance is a very rare genetic (inherited) condition, where the body does not produce any lactase and is a life-long condition.
Secondary lactose intolerance is caused by inflammation (swelling) of the gut, where the body does not produce enough lactase. This can be caused by infection, cancer treatment or other gut conditions and can be short or long term. This FAQ is focused on secondary lactose intolerance.

Q 3: What are the symptoms of lactose intolerance?

When people with lactose intolerance consume products containing lactose, they may get symptoms that can be uncomfortable, including:

Bloating
Gas (wind or flatulence)
Stomach upset
Diarrhoea

These symptoms usually happen straight after eating or drinking a product that contains lactose. This occurs because lactose moves through the gut without being broken down by lactase. Lactose draws water into the gut and when it gets to the large intestine (a part of the gut), it is broken down by bacteria which produce gas. It can be hard to know if symptoms are caused by lactose intolerance or by another medical condition, so it is important to talk to your doctor or dietitian before changing your diet.

Q 4: How is lactose intolerance different to cow’s milk protein allergy?

Cow’s milk protein allergy involves the immune system (IgE mediated) and is different to lactose intolerance. People with lactose intolerance will have negative allergy tests to cow’s milk protein.

Treatment of cow’s milk protein allergy is different from lactose intolerance. Lactose free formula or milk is not suitable for people with cow’s milk protein allergy. People with cow’s milk protein allergy can have symptoms such as skin swelling or rashes, vomiting, wheeze, cough and severe allergic reactions (anaphylaxis). If you get any of these symptoms, you should talk to your doctor.

Although lactose intolerance symptoms can be uncomfortable, it does not cause anaphylaxis.

Q 5: How is lactose intolerance diagnosed?

Lactose intolerance can be diagnosed in different ways, which include:

Elimination of lactose from diet for a short time then reintroducing it while monitoring symptoms.
Hydrogen breath test. After consuming lactose, more hydrogen is in the breath of people with lactose intolerance.
In some cases, doctors may take a biopsy (tissue sample) during a gastroscopy, which is a medical procedure, to check the levels of lactase enzymes in the gut.

Q 6: How is lactose intolerance managed?

Lactose intolerance can be managed in different ways:

Lactase enzyme drops or tablets from a pharmacy can be taken before, or added to, regular dairy products to help digest the lactose.
Lactose can be minimised in the diet by consuming lactose free products. Speaking to your doctor or dietitian can help work out what level of lactose you can tolerate to avoid diet restrictions that are not needed.
For babies with lactose intolerance, lactose free formula is available. It is important that this is not fed to a baby with cow’s milk protein allergy.
Some people are highly sensitive and may need to avoid medications that contain lactose.
With short term lactose intolerance, lactose may be reintroduced into the diet after it has resolved.

People with lactose intolerance can still produce a small amount of the lactase enzyme, which means that tolerance can vary between people. For example, one person may be able to tolerate a small cup of regular cow’s milk while another may tolerate only a small amount of cow’s milk in tea or coffee.

Q 7: Are there any products available that are low in lactose?

People with lactose intolerance do not always need to avoid all dairy foods, unless they also have a confirmed cow’s milk protein allergy. Some dairy products are naturally low in lactose and are often well tolerated by people with lactose intolerance. These products include:

Small amounts of hard or matured cheeses such as cheddar, Edam, Swiss, mozzarella, brie, camembert and fetta.
Small amounts of cream and fresh cheeses such as cottage cheese and ricotta.
Pot set yoghurt, which is lower in lactose than normal yoghurt.
Butter and margarine.

Q 8: Are lactose free products available?

It is important to choose lactose free foods and drinks that contain similar levels of nutrients, such as protein and calcium, as regular dairy products. A dietitian can help with this.

Lactose free dairy products are widely available, including:

Lactose free cow’s milk, yoghurt, cheese, cream, ice cream and custard.
Soy milk and yoghurt do not contain lactose. Choose products that have added calcium (calcium fortified).

Content developed August 2024

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