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food allergy

What is the difference between a food intolerance and a food allergy? 


The world of allergy may often feel completely inaccessible simply because of the vocabulary that gets used on the internet, in the media and by health care professionals. Intolerance and allergy often get used interchangeably and they really shouldn’t be as they are completely different conditions and involve different management strategies.


In this blog post, dietitian Sasha explains how to tell the two apart using the example of a milk allergy vs. lactose intolerance.

Food allergy


It’s very importance to distinguish between whether or not the body’s immune system is involved and doctors now distinguish between ‘Allergic Hypersensitivity’ and ‘Non-Allergic Hypersensitivity’.


A food allergy such as cow's milk allergy falls under the banner of ‘Allergic Hypersensitivity’ as your immune system is involved and you may have a quick reaction to even a tiny amount of that food. Symptoms may include swelling of the eyes, lips, tongue and roof of the mouth, itchiness in the mouth, ears or throat and rash where your skin is raised, red and itchy.


Not all allergic symptoms are immediate and some may occur up to 72 hours after consuming milk such as eczema, reflux, loose stools, mucus and/or blood in the stools, constipation. When you have an allergy to milk, you are reacting to the proteins in the milk and that is why the condition is often referred to as ‘cow’s milk protein allergy’. To manage the condition, all forms of cow’s milk may need to be taken out of your diet.

Lactose intolerance


Lactose intolerance does not involve the immune system so is classed as ‘Non-Allergic Hypersensitivity’ and symptoms are rarely immediate. Lactose intolerance is a digestive problem where the body is unable to digest lactose, a sugar commonly found in dairy products. Normally the enzyme lactase is responsible for breaking down lactose into smaller compounds so our bodies can absorb it. In the case of lactose intolerance, there is absence or deficiency of lactase, which leads to symptoms of bloating, nausea, wind, abdominal pain, constipation or diarrhoea.


Lactose intolerance may be managed by reducing the amount of cow’s milk (rather than completely removing all cow’s milk) you have in your diet. Most individuals with lactose intolerance can tolerate some lactose, although the amount varies between individuals. Yoghurt and hard cheese may be fine as these have lower levels of lactose than regular milk. Lactose free milks are a good alternative to cow’s milk containing alternatives as they generally contain the same amount of key nutrients such as calcium but have a low lactose content. Lactose free milks are not suitable as a management strategy for cow’s milk allergy, as they still contain cow’s milk proteins, which could cause an allergic reaction.

Please see your GP


If you suspect you may have a food allergy or intolerance, please book an appointment with your GP. Please avoid self-diagnosis and doing unreliable high street tests.


Home tests or allergy tests available on the high streetsuch as hair analysis, vega tests, applied kinesiology, serum-specific IgG tests are not recommended at all in the diagnosis of food allergy. They are unreliable tests and may be very expensive.


Irrespective of which condition you have, it is always advisable to get a referral to see a dietitian so she/he can ensure you diet is balanced and getting all the nutrients you needs for good health.

Sasha Watkins

Registered dietitian and co-founder of Field Doctor

IG: @sashadietitian

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