Allergy and intolerance
IgE antilichamen koemelk
Antibodies against milk protein; shows whether the immune system is sensitive to cow's milk, not whether it gives you symptoms.
Everything about this testWhat it measures
This test measures the amount of IgE antibodies against the proteins in cow's milk in the blood. IgE is the type of antibody that, in an allergic reaction, prompts mast cells to release histamine. The body only makes such antibodies after it has been in contact with the allergen before; this is called sensitization. The result is a number in kU/l; the laboratory indicates from which value the result counts as positive.
- Sensitization to cow's milk: the body has made IgE antibodies against cow's milk
- Support in investigating a suspected allergy to cow's milk, together with the story of the symptoms
- Support with the question of whether symptoms after milk fit an allergy rather than lactose intolerance
High
A value above the cutoff means that you have IgE antibodies against cow's milk: sensitization. This is not the same as an allergy. Cow's milk allergy mainly occurs in the first year of life and goes away again in most children: just over half tolerate cow's milk again around their first birthday. As with egg, the IgE result often stays positive while the child already tolerates milk again. According to the Dutch Pediatric Society (NVK), children with an IgE-mediated cow's milk allergy often also react to goat's milk, sheep's milk and other animal milk; they do not need to avoid soy products. According to the Dutch Society for Clinical Chemistry (NVKC), the level of the result says nothing about how severe a reaction would be, although a clearly higher value does go with a greater chance that there really is an allergy.
Low
A value below the cutoff means that no IgE antibodies against cow's milk have been found. An IgE-mediated allergy to cow's milk is then a lot less likely. In some young children, the symptoms are not IgE-mediated; the test is then normal even though there is a cow's milk allergy. Lactose intolerance is not an allergy and cannot be seen with this test. Symptoms after eating can also have another cause, for example an intolerance or a bowel condition.
If your result is abnormal
The GP mainly looks at the story: which symptoms, how soon after eating and how often. Often a food diary follows, along with temporarily leaving out the suspected food and then reintroducing it. If a true allergy is suspected or after a severe reaction, a referral follows to an allergist or pediatrician, where a food challenge test is done if needed; according to the Dutch medical specialists' guideline (FMS), this test is the gold standard.
Reliability
A positive IgE result shows sensitization, not allergy: it only means that there are antibodies, not that cow's milk gives you symptoms. The pooled specificity of the IgE test for cow's milk in the Dutch medical specialists' guideline (FMS) is 48 percent: about half of the people studied without a cow's milk allergy still have a positive result. Because a positive result also occurs in people without an allergy, the result can cause confusion when viewed separately from the symptoms. The result can only be interpreted together with the story of the symptoms and, if in doubt, with a food challenge test in the hospital.
Limitations
- In children, the result often stays positive after the allergy has already gone away.
- A cow's milk allergy that is not IgE-mediated gives a normal result.
- Lactose intolerance, a problem with digesting milk sugar, cannot be shown or ruled out with this test.
- Laboratories use different measuring methods; results from different labs cannot always be compared one to one.
How common is this
The Netherlands Nutrition Centre (Voedingscentrum) estimates that 2 to 3 in 100 children develop a cow's milk allergy in their first year of life; this makes it the most common food allergy in babies. According to the Dutch Pediatric Society (NVK), the IgE-mediated form occurs in about 0.7 in 100 children. In adults, cow's milk allergy is rare.
Who is this useful for
The result says the most when there has been a clear reaction shortly after consuming cow's milk, as an addition to the conversation with the doctor. In people who consume cow's milk normally and have never had an acute reaction to it, a positive result does not mean that you are allergic and can lead to unnecessarily avoiding cow's milk. With vague symptoms such as abdominal pain, tiredness or eczema without a clear link to a meal, the test adds little. For a baby with a suspected cow's milk allergy, testing goes through the child health clinic, the GP or the pediatrician.
Downsides and risks
- A positive result without symptoms easily leads to cow's milk being unnecessarily left out of the diet. This can lead to a shortage of nutrients and, according to Thuisarts.nl, can actually increase the chance of an allergy, especially in children.
- A normal result does not rule out symptoms caused by cow's milk: there are people with symptoms in whom no IgE antibodies can be found in the blood.
Sources
- NHG-Standaard Voedselovergevoeligheid en coeliakie (M47)
- FMS Richtlijnendatabase: Voedselprovocatie, module Plaatsbepaling diagnostiek voedselallergie
- NVK-kennisdocument: IgE-gemedieerde koemelkallergie bij kinderen
- Voedingscentrum: Koemelkallergie
- Thuisarts.nl: Ik denk dat mijn kind niet tegen bepaald voedsel kan
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results