A cows’ milk allergy, also known as cows' milk protein allergy, can occur when cows' milk -- consumed by the mother of a breastfeeding baby or used in formula for bottle-feeding babies -- causes symptoms in the baby before being weaned, or if the baby consumes cows’ milk protein-containing products during or after weaning. The allergy usually appears in the first year of a baby's life, but most children will outgrow it.
How Common Is Cows’ Milk Allergy in Infants?
Cows' milk allergy is one of the most common food allergies in the UK, affecting about 7% of infants who are formula-fed or fed both formula and breast milk. It can also occur in exclusively breastfed babies, but only 0.5% of these babies are affected, and the symptoms are usually mild or moderate. This is one reason breastfeeding exclusively is recommended by experts for the first 4 to 6 months of a baby's life.
It is thought that infants who have a family history of allergy are more likely to have a cows’ milk protein allergy. Same goes for infants with eczema and asthma. Those with asthma can have severe reactions, especially if their lung disease is poorly controlled.
What Causes Cows’ Milk Allergy?
An allergy occurs when the body's immune system mistakes a harmless substance -- in the case of food, a protein -- as a foreign invader and attacks it, much like it would attack bacteria or a virus. This abnormal response releases chemicals that in turn trigger the symptoms associated with an allergy.
Milk contains both casein (which forms the curd when milk goes sour) and whey (the watery bit when the curd is removed), and each of these has several different proteins, any of which can cause an allergic response.
A cows' milk protein allergy can cause different kinds of reactions, depending on the chemicals released, and the allergy is categorised based on these causes:
- Immunoglobulin E (IgE)-mediated reactions: The immune system releases histamine and other chemicals in response to cows' milk protein. The symptoms usually occur within 20 to 30 minutes of consuming the protein, but they can appear up to 2 hours later.
- Non-immunoglobulin E-mediated reactions: T cells are thought to be the trigger for the symptoms, which appear more gradually, from 48 hours up to a week after consuming cows' milk protein.
- Mixed IgE and non-IgE reactions: This is a combination of immunoglobulin E-mediated reactions and non-immunoglobulin E-mediated reactions.
A cows’ milk allergy should not be confused with lactose intolerance, a condition in which the body cannot produce enough of the enzyme needed to digest a type of sugar found in milk.
What Are the Symptoms of Cows’ Milk Allergy?
There are a wide range of symptoms that can be triggered by a cows' milk protein allergy, usually involving the skin, gastrointestinal tract, and respiratory tract. Those that involve the respiratory tract often occur along with other symptoms. These include:
IgE-mediated symptoms (these are acute and occur more quickly)
- Skin reactions: Itchiness, reddening of the skin, sudden itchy rash (urticaria -- either in one spot or generally all over), or swelling, most often of the lips, face, and around the eyes
- Gastrointestinal reactions: Swelling of the lips, tongue, or palate in the mouth, itchiness in the mouth, nausea, vomiting, colicky abdominal pain, or diarrhoea
- Respiratory reactions: Itchy nose, sneezing, runny nose, congestion, cough, wheezing, or shortness of breath
Non-IgE-mediated symptoms (these are non-acute and are delayed)
- Skin reactions: Itchiness, reddening of the skin, or eczema
- Gastrointestinal reactions: Acid reflux or gastro-oesophageal reflux disease (GORD), loose or frequent stools (poo), blood or mucus in poo, abdominal pain, colic, constipation, refusing food or aversion to food, redness in the perianal area, tiredness
- Respiratory reactions: Cough, wheezing, or shortness of breath
In rare cases, a child may have an anaphylactic reaction, which requires emergency medical help straight away because it can be fatal. Call an ambulance if you think your infant is struggling to breathe or is floppy.
A cows' milk protein allergy can sometimes lead to complications due to malabsorption or poor nutritional intake. The child may get chronic iron deficiency anaemia or fail to thrive.
How Is Cows’ Milk Allergy Diagnosed?
If you suspect your infant might have a cows' milk protein allergy, make an appointment to see your GP, who will ask about the child's family history to find out if other members of the family have a food allergy, asthma, eczema, or allergic rhinitis. The GP will want to know all about the symptoms and when they first appeared.
Before confirming a diagnosis of cows’ milk allergy, other conditions that may cause similar symptoms -- such as a food intolerance, other food allergies, Crohn's disease, coeliac disease, and GORD -- may need to be ruled out.
If the doctor suspects an IgE-mediated cows' milk protein allergy, your infant will usually be referred to an allergy specialist for a skin prick test and/or an IgE antibody blood test. If confirmed, then strict avoidance of cows’ milk protein is needed.
For suspected non-IgE-mediated cows' milk protein allergy, the GP may not need to refer your child to a specialist. But a referral will be made if there are concerns about your child's growth or symptoms are acute or severe. Based on the child's symptoms -- and provided a referral to a specialist is not necessary -- your doctor can recommend trying an elimination diet in which cows' milk protein is eliminated from the child's diet -- or the mother's if the infant is totally breastfed -- for a medically-advised period of time. If a cows' milk protein is responsible for the symptoms, this allows them to disappear -- and the symptoms will reappear when cows' milk protein is reintroduced to the diet at an appropriate time in the future as recommended by your doctor, confirming the diagnosis.
Beware of complementary or alternative health tests for food allergy, such as hair analysis or applied kinesiology. There is no scientific evidence that they work, and an incorrect diagnosis of a food allergy or intolerance may lead to unnecessary dietary exclusions. Cutting out a large number of foods on the basis of these tests can lead to nutrient deficiencies that can mean your child may fail to thrive.
Can an Infant Outgrow Cows’ Milk Allergy?
Most children will outgrow cows’ milk allergy.
Studies show that most children with non-IgE-mediated reactions will outgrow cows’ milk allergy by the time they are 3 years old.
For children with IgE-mediated reactions, studies show that about half of these children will outgrow cows’ milk allergy by the time they are 5 years old. Evidence suggests that a cows' milk protein allergy is more likely to persist in these children if they have asthma or allergic rhinitis, or if they have more severe reactions or higher milk-specific IgE antibody levels. Even so, it is rare for adults to have a cows’ milk allergy.
Will My Infant Need Any Treatment?
If cows’ milk allergy is diagnosed, cows' milk protein will need to be eliminated from your child's diet. A paediatric dietitian or health visitor can provide you with advice on either breastfeeding an infant with cows’ milk allergy or bottle-feeding an infant with cows’ milk allergy.
You will also be given advice on how to wean your child following a diet that excludes cows' milk. Because cows' milk provides a lot of important nutrients, especially calcium, a paediatric dietitian or health visitor can help ensure that your child is getting enough of all the nutrients necessary for healthy growth.
You should be given a management plan that will not only include how to feed your child, but also treatment, such as antihistamines or creams in cases where a child has eczema. Follow-up appointments should continue to ensure your child is thriving.
Because children can outgrow cows’ milk allergy, your child should be re-assessed as often as your doctor recommends, to determine if there is a change in tolerance of cows’ milk protein.