What is Lactose Intolerance?

Many people who have an adverse reaction to dairy products think they are allergic to milk this is not always the case. A food allergy is defined as any adverse reaction to an otherwise harmless food or food component that involves the body's immune system. Therefore when talking about a food allergy it only involves the body's immune system.

A food intolerance is when you develop symptoms after eating a food product that your body can't deal with adequately. With milk products this is because the digestive system does not produce enough of or any lactase (an enzyme found in the stomach), which breaks down lactose ( the sugar found in dairy products), to a simpler sugar which can be digested. The symptoms include stomach cramps, bloating etc. (see Symptoms and diagnosis).


How do you know if someone in your family is Lactose Intolerant or allergic to milk? The symptoms of a milk protein allergy fall into 3 types of reactions

Skin Reactions:

Stomach and Intestinal Reactions:

Nose, Throat and Lung Reactions:

As you can see most of these symptoms can be seen in people who have asthma or hayfever or a cold. They could have indigestion or a reaction to a chemical or plant they handled. Milk is not always the first choice for doctor to look at when you go to them with any or all of the above. Other symptoms have been recorded such as muscle weekness or spasms, but more research is required.

However, a milk allergy (rather than an intolerance) can be life threatening and an anaphylactic reaction can occur.
Anaphylaxis means "Without Protection". It is a severe reaction by the body to an offending Allergen (something causing the allergy), and it happens very fast, within minutes of exposure. Foods that commonly cause this reaction are peanuts, tree nuts, milk, eggs, shellfish and fish. Drugs also can cause a reaction these include penicillin, Sulphur and aspirin. Bites and stings from insects such as bees, wasps and ants can cause an anaphylactic reaction. An anaphylactic reaction involves more than one system of the body. It can begin with a tingling sensation in the lips, tongue or throat, this progresses to red raised itchy rash, feeling dizzy asthma symptoms, change in blood pressure and loss of consciousness and collapse.

What tests are available?

A range of tests can be taken to find out what you are allergic to or have an intolerance the most common is the RAST Test (RadioAllergoSorbent Test). This test is used to see if you have any antibodies, particularly the antibody IgE, against a specific allergen in your blood. Basically a sample of blood is taken added to the food that might be the cause, a radioactive marker is added aimed at the antibody IgE. The sample is then measured to see how much IgE is present in the blood. The test however is not perfect as a positive result can be obtained if the food contains anything that will specifically bind to IgE that is already in the blood sample.

The other test is a Skin Prick Test. Here a few drops of a highly diluted solution of the allergen is put on the skin, the skin is then scratched and the weak substance leaks under the skin. After 15 minutes the allergist examines the test area for a zone of redness. This zone is measured to give a level of reaction, depending on the severity of the the large the zone the more severe the allergy. This procedure is carried out by a doctor or qualified nurse.

(Please bear in mind that these test are mainly for allergies rather than intolerances and you should speak to your doctor or health professional before undertaking these test.)

Nice - The National Institute of Health and Clinical Excellence has produce some guidance in February 2011 for Allergy and Intolerance test for children. Click here for the guidance material.

If however you think you or a member of your family are intolerant to dairy products rather than allergic there are three types of tests available to measure lactose absorption in the digestive system. The first is the Lactose Tolerance Test. The test begins with a fast for 24 hours and blood is taken and the glucose level tested. Then a drink of lactose is given and for the next 2-3 hours blood samples are taken to see how much glucose is in your blood, and this will determine if lactase is present in your digestive system. This test is not used on young children.

The second test is the Hydrogen Breath Test. Normally no hydrogen is produced in a normal gut, however undigested lactose produces various gases including hydrogen. The test can be affected by certain foods and drugs, and smoking so may not be very accurate. This test is not normally used on young children, however the test is being used more recently.

The final test is the Acid Stool Test. This measures the amount of acid in stools. Undigested lactose is fermented in the lower bowel and creates lactic acid which can be simply measured. This test is used for young children and gives some idea if the child is lactose intolerant.

Another test available is the Enzyme-Linked Immunosorbent Assay (ELISA). This is a food sensitivity test that measures the amount of the antibody IgG your immune system produces in response to a specific food group you are sensitive. The test is carried out by taking a tiny sample of blood (a pin prick). The sample is then tested for the antibody against each food group and any raised levels of antibody show you have a sensitivity to that food group. This is the test used by most of the home testing companies (see below for some companies that offer this type of test).

The following tests are also available however they are usually carried out by unqualified people and often give false readings.

Vega Test
This is an electrical test where the machine measures the conductivity between electrodes either held in the patient's hand or to acupuncture points. Different solutions are then placed in a metallic tray . Then the machine is calibrate by place a vial containing a toxic substance in the tray, the vial causes a reduction in electrical conductivity. Other substances are then placed in the try and if similar readings are seen they are reported as an allergic or sensitive reaction. These tests are usually carried out in health food store by unqualified people who advise the patient to eliminate various foods, sometime to the detriment of the patient. Elimination diets should only be prescribed by a qualified dietician or nutritionist. The BMA recommends that Vega testing should be avoided.

Leucocytotoxic test
In this test the patient's white blood cells are mixed with extracts of specific foods and the cells are measured for evidence of some form of change. Various false positive and false negative results are seen and although various tests have been carried out they have been shown to be unscientific.

Hair Analysis
Here a sample of hair is tested for toxic metals. However hair analysis as a means for diagnosing an allergy has never been validated. The test will only tell you if you have been exposed to heavy metals.

Applied Kinesiology
Patients are asked to hold samples of food either under their tongue or in a glass container in their hand. The patient is then asked to press their free arm against the examiner. An allergic response is detected if the patient does push as hard as prior to holding the food (a reduction in muscle response). It has been difficult to find any scientific evidence for this test and in fact the test failed a double blind study.

Most of the material above has come from The non dairy, organisation (now closed)and Gastroenterology group of Naples (USA) see links.

A number of private test facilities are available,  most have been shown to be a waste of money ( see articles by The Sunday Times and Which? Consumer Association magazine). Please speak to your GP, allergist of dietician first before embarking on these expensive tests.

However if you wish to try one of the postal test then visit   York Test Laboratory Site.  York Test Laboratory have a range of tests for food  allergies and sensitivities. These tests examine the amount of food specific IgG antibody your body produces against the food type you are sensitive to, by using the Enzyme-Linked Immunosorbent Assay (ELISA) method. York Test Laboratory Site will supply more information and the cost for the test (dependant on the number of foods tested. The company supply and sample kit for you to use and return to the laboratory. They also will carry out tests for vegetarian food sensitivity, Helicobacter pylori (the ulcer bacteria) and a hair mineral analysis. You can write to  Genesis 3  at York Science Park,York,YO10 5DQ, Tel: Freephone 0800 074 6185 (UK only) or +44 (0) 1904 410 410, Fax: 01904 422000 or email customercare@yorktest.com and of course by visiting their site by clicking the heart logo. York currently offer milk intolerance tests not lactose intolerance.

Another company you can try is Cambridge Nutritional Sciences Ltd. The company provides a special blood collection kit which allows collection and safe transport of the sample to their laboratory for analysis. The cost of the test is similar to the other companies. Their address is Cambridge Nutritional Sciences Ltd, Eden Research Park, Henry Crabb Road, Littleport, Ely, Cambridgeshire CB6 1SE Tel: 01353 863279 Fax : 01353 863330.


I have recently been asked about Galactosemia (a high blood level of galactose). This is a genetic disorder usually caused by the lack of the enzyme Galactose 1-phosphate uridyl transferase. The disorder is present from birth.
The absence of Galactose 1-phosphate uridyl transeferase can be tested by a urine or blood test if family members are known to suffer from galactosemia.
Milk and milk products must be completely eliminated from the diet and because galactose is also found in some fruit vegetables and sea products, such as seaweed, these should also be avoided.
For more information there are a number of sites worth visiting see the British links.

Labelling of commercial products

One of the biggest problems for people who have allergies, especially in the UK, is that the information on labels of prepared food is often inadequate, confusing and inaccurate.

This situation affects those who are allergic or intolerant to food, food is bought in good faith, the label checked for the allergen, but the product could well have been produced on the same line as products containing milk, wheat, shellfish, nuts, etc.

In 1998 the UK government published a white paper for the setting up and objectives of the Food Standards Agency. This paper can be viewed from A force for change. The paper is important and you can e-mail comments to the ministry regarding labelling, etc. Recently the setting up of the FSA was discussed in Parliament, however most of the debate was taken up with GM food and so we still have no firm decisions on how the FSA will work other than all companies who sell food will have to pay to fund the FSA. Since then new regulations have existed and as of 13 December 2014 new changes to labelling will come into force in the UK. Click here for details. The FSA has also produced new guidance (August 2013) for people who have a food allergy or intolerance. The FSA site also has online training courses for food establishments.

For more information about food labelling read Sue Dibb's book "What the label doesn't tell you". Sue is a co-director of the Food Commission and a regular contributor to the BBC's Good Food magazine. Sue deals with hidden milk products and other allergens. The book is well worth reading. Book information

This page has been around since 3 March 1998. Thanks for the support.

This page was last updated Wednesday, 31-Aug-2005 20:30:35 GMT