Milk proteins and lactose

Allergy to milk is a reaction to the proteins in contrast to lactose intolerance, where the milk sugar, i.e. lactose is causing the problems. Individuals with milk protein allergy must avoid all milk products including cheese. Individuals with lactose intolerance tolerate cheese and small amounts of milk products.

Allergy to milk proteins

Milk protein allergy is a serious condition. Even tiny amounts of milk/milk proteins can elicit severe allergic reactions in sensitized individuals. Cow's milk contains a number of different proteins. Caseins and the whey proteins lactoglobulin and lactalbumin are present in highest concentrations. Allergic individual may react to one or several of these milk proteins. In addition, other proteins in cow's milk have been associated with allergic reactions.

Milk is a common ingredient in the following food: buns, cakes, cookies, meringues, potato gratins, pâtés, meatballs, hamburger, sausages, powder for gravy, legume salads, pancakes, waffles, omelet's, sweets, toffees and chocolate.

Milk might also be an ingredient in bread, mashed potatoes, vegetable soups, stews, fruit/berry desserts, curd, vanilla cream, ready to eat dishes with meat, fish and egg as well as mayonnaise. Bread can be brushed with milk or milk protein (casein).

Lactose intolerance

Lactose (milk sugar) is a natural component in all kinds of milk. Lactose intolerant individuals have reduced levels of an enzyme, lactase, needed to hydrolyze lactose in the small intestine. Lactase deficiency allows the lactose to reach the large intestine where it is fermented by the colon micro flora.

Symptoms of lactase deficiency are stomach/intestinal distension accompanied with pain, flatulence and diarrhea. The individual sensitivity to lactose varies but most individuals tolerate small amounts of lactose, corresponding to 100 ml of milk per day.


The presence of milk and products thereof including lactose in food products must always be declared, see further in the Food Information Regulation (EC) no 1169/2011.

Examples of methods of analysis

The caseins are the dominating proteins in milk and constitute about 80 percent of the proteins. The caseins are heat stable and thus suitable for the analysis of milk/milk proteins in food. The whey proteins are the residual proteins in milk after removal of the caseins, i.e. about 20 percent of the proteins in milk.

Lactoglobulin is one of the proteins in the whey fraction. Lactoglobulin is not as heat stable as the caseins but can be used as a complement for the analysis of milk in food products. The caseins are a better indicator for the presence of milk/milk proteins in compound food products unless only the whey fraction was included in the product to be analyzed.

Sensitive commercial ELISA test kits are available for the analysis of casein and lactoglobulin. The limit of quantification varies somewhat between different test kits and depends also upon the matrix. The limit of quantification for casein is as low as 0.5 mg/kg in certain matrixes.

Lactose can be quantified with an enzymatic method (lactose/galactose). The limit of quantification is just below 100 mg/kg. The enzymatic method is not suitable for the analysis of products where lactase has been added for the hydrolysis of lactose. Such products can be analyzed with chromatographic methods like HPLC or GC.

Accredited methods should be used in official control. The National Food Agency is accredited for analysis of casein and lactose/galactose in food.

Allergic reactions / Doses

The lowest dose of milk proteins/caseins that elicits an allergic reaction is not known. The table below shows information about the concentrations of casein detected in food products that have caused allergic reactions.

The National Food Agency has developed a guide on how to calculate the risk of allergic reactions to certain concentrations of milk. The guide is in English and can be reached below.

Food Consumed amountCasein conc. mg/kgEstimated dose  Reported reaction Age
Candies 30 g 30  0.9 mg Anaphylactic reaction* emergency treatment  6 years
Yoghurt (soy-based) 15 ml 107  1.5 mg Serious allergic reaction, emergency treatment  18 years
Chocolate coated mallow 5 g 1200  6 mg Anaphylactic reaction* emergency treatment   9 years
Dark chocolate 9 g 779  6.9 mg Allergic reaction 12 years 
Biscuit 25 g 300  7.5 mg Vomiting, breathing problems  10 years
Potato chips 40 g 830  36 mg Fatal anaphylaxis**  10 years
Ice cream (soy-based) 5 g 2000  10 mg Swelling of lips and tongue  3 years
Soy-based infant formula 250 ml 40  10 mg Asthma, vomiting  3 years
Chocolate 3 g 4000  12 mg Stomach pain, vomiting  9 years
Chocolate 25 g 1300  32 mg Urticaria, vomiting  3 years
Chocolate cake 82 g 800  66 mg Allergic reaction  5 years
Chocolate 50 g 2900  145 mg Stomach pain  14 years
Chocolate 50 g 5400  270 mg Stomach pain  14 years
Sausage 50 g 400  20 mg Vomiting, urticaria  6 years
Sausage 50 g 800  40 mg Vomiting, breathing difficulties   5 years
Sausage 100 g 600  60 mg Fatal anaphylaxis  15 years
Sausage 10 g  19  1.9 mg Allergic reaction  m
Sausage 10 g 11000 100 mg Urticaria, vomiting, breathing difficulties  3 years
Sausage 25 g 5000  125 mg Stomach pain  6 years
Sausage 25 g 16000  400 mg Vomiting, diarrhea  3 years
Sausage 25 g 17000  425 mg Stomach pain, vomiting  11 years
Meatballs 20 g 890  17 mg  Oral allergy syndrome, stomach pain



* Anaphylactic reaction means that the allergic individual suffers from blood pressure drop, respiratory comprise/cramps in the airways and a systemic reaction, called anaphylactic shock

** Fatal anaphylaxis means that the shock proceeds to unconsciousness and death

Reviewed 2019-12-16