Food intolerance and allergies have different causes but similar symptoms. Here, we describe what causes these conditions and how they are diagnosed and treated.

The difference between food intolerance and food allergy

Food intolerance is an inability to properly digest certain types of foods, whereas food allergies are an immune system reaction to eating a particular food.

Food intolerance

If your body can’t digest a particular type of food, this can make you feel unwell – this is food intolerance. Food intolerances are not usually life-threatening. However, it’s important to diagnose food intolerances in individuals to prevent long-term health problems.

Types of food intolerance

The common food intolerances are:

  • lactose (milk)
  • yeast
  • gluten (a protein in grains such as wheat, barley and oats)
  • sugar

Lactose intolerance is the most common food intolerance and occurs in about 75% of the world’s population. However, New Zealanders with ancestors from northwest Europe can often digest lactose because they’ve inherited a genetic mutation that allows them to do this.

Find out more about genes and lactose intolerance.

Symptoms of food intolerance

Symptoms of food intolerance can include nausea, bloating, vomiting and diarrhoea. These symptoms are similar to those seen for a food allergy, so these conditions can be difficult to tell apart.

Diagnosis and treatment of food intolerance

The simplest way to diagnose food intolerance is to remove the food from your diet and see whether symptoms improve. Also, doctors can test for specific food intolerances. For example, lactose intolerance can be diagnosed using a lactose tolerance test, a hydrogen breath test or a genetic test.

Find out more about a genetic test for lactose intolerance.

The best way to treat food intolerance is to remove or reduce the food from your diet. However, biotechnology has come up with some novel ways of treating lactose intolerance.

Food allergy

Your immune system keeps you healthy by attacking and removing disease-causing organisms like bacteria or viruses. If you have a food allergy, your immune system mistakenly attacks a food substance. Fortunately, food allergies are rare (only 1–2% of the world’s population are affected).

Any substance that causes an allergy is known as an allergen. Common food allergens include milk, eggs, peanuts, tree nuts (such as brazil nuts, hazelnuts, pecans and walnuts), fish, shellfish, soy and wheat.

Symptoms of food allergy

Food allergy symptoms occur rapidly and can be mild (skin rashes, itchy eyes and nose, wheezing, coughing and nausea) or serious (vomiting and diarrhoea). In rare cases, people experience anaphylaxis, which can stop breathing and is life-threatening.

Diagnosis and treatment of food allergy

A medical examination and blood tests are required to diagnose a food allergy. Blood tests can detect whether the immune system is producing antibodies against a particular food. If you have a food allergy, you must avoid the food that causes the reaction.

Useful links

Information on the causes and symptoms of food allergies and intolerances from the Ministry for Primary Industries.

An article explaining the difference between food intolerance and allergies from Allergy New Zealand.

A summary of food allergies from foodreactions.org. The information is adapted from the research by Dr Clare Mills at the Institute of Food Research, Norwich, UK.

 

    Published 3 September 2009