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 (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 amount||Casein conc. mg/kg||Estimated 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