Cow’s milk allergy terms explained

To help you along your journey from diagnosis to treatment, we have created a handy guide which contains explanations of common medical terms related to cow's milk allergy (CMA). Always ask your doctor or other healthcare professional for more information if you have any concerns or need further clarity.



The part of your body below your chest where your stomach and intestines are located. Commonly known as the belly.1


A substance, most often a protein, that causes an allergic reaction.2

Allergic Reaction.

Occurs when the body’s immune system overreacts to an allergen. The immune system normally protects the body from infections and diseases, however, in some people, allergens may trigger the production of antibodies called immunoglobulin E (IgE). These antibodies cause a release of chemicals that cause symptoms, most often in the nose, throat, skin or gastrointestinal tract.3


A doctor who specialises in the diagnosis and treatment of allergies.4 


A condition involving an abnormal reaction to an ordinarily harmless substance, also known as an allergen, such as cow’s milk protein, pollen or nuts.3

Amino acid.

A small molecule that serves as a building block for protein.5

Amino acid-based formula (AAF).

A hypoallergenic formula formed of amino acids. Amino acid-based formulas contain no milk protein, to prevent an allergic reaction in infants with cow’s milk allergy. This type of formula is also sometimes shown as elemental because it is formed of the simplest form of proteins, amino acids.6,7


A life threatening allergic reaction typically involving the whole body. Symptoms can include distressed breathing, throat and tongue swelling, low blood pressure, intense stomach pain, vomiting and hives.2,8


Also known as immunoglobulins, antibodies are Y-shaped proteins that are produced by the immune system to help stop invaders from harming the body. When an invader enters the body, the immune system springs into action. These invaders, which are called antigens, can be viruses, bacteria, or chemicals. There are several classes of antibodies including immunoglobulin G (IgG), which are most important to protect against infections.9


A group of drugs that block the effects of histamine, a chemical released in body tissues and fluids during an allergic reaction.9


A common lung conditon characterised by recurrent breathing difficulties. People with asthma have acute episodes when the air passages in their lungs get narrower and breathing becomes more difficult. Sometimes episodes of asthma are triggered by allergens, although infections like cold or flu, exercise, pollution and other factors are also important triggers.2,10

Atopic dermatitis.

See eczema.



A condition in which the abdomen feels full and tight and may appear swollen. It may be a result of food intolerance or allergy.11

Blood test.

A scientific examination of a sample of blood, sometimes performed to diagnose IgE-mediated reactions to allergens. A blood test for cow’s milk allergy will typically involve taking a sample of your baby’s blood and analysing it for a specific IgE antibody (previously referred to as a RAST test).12-14



A major protein component of cow’s milk that can trigger an allergic reaction in infants and children with cow’s milk allergy. Alimentum is made from casein protein that has been extensively broken down into little fragments that the immune system of most babies with CMA cannot recognise or react to.15,16


Frequent, prolonged and intense crying or fussiness in a healthy infant for no apparent reason. Colic usually starts a few weeks after birth and stops by the sixth month. The causes of colic are unknown, but some experts think that some cases of colic could be the result of an allergy to cow’s milk proteins.17-19


A disease or medical condition present from birth.20


A common condition in which there is difficulty in emptying the bowels, usually associated with hardened faeces.21

Cow’s milk protein.

Protein components such as casein and whey that are made from cow’s milk. Babies with cow’s milk allergy have an allergy to cow’s milk protein.15,16



See eczema.


This is when the stool (faeces) is loose, frequent and watery. There are a number of different causes of diarrhoea. A bowel infection (gastroenteritis) is a common cause and diarrhoea can also be the result of a food allergy.22


A qualified and regulated healthcare professional that assess, diagnose and treat dietary and nutritional problems at an individual and wider public-health level.23

Double-blind placebo-controlled food challenge (DBPCFC).

This test is considered the gold standard for diagnosing food allergies such as cow’s milk allergy and is also used in clinical trials. An infant with suspected cow’s milk allergy will receive increasing doses of cow’s milk and a placebo (a harmless substance that doesn’t contain cow’s milk). The cow’s milk and the placebo are given separately, either hours apart or on separate days. As the allergen and the placebo look alike, neither you or the healthcare professional will know which one you are receiving, hence the term ‘double-blind’. The healthcare professional then monitors the baby for a period of time to determine whether there is a reaction to cow’s milk. These tests are only performed in a setting with medical supervision in case of a severe reaction.14,24



A common skin condition that causes the skin to become itchy, inflamed and have a rash-like appearance. Atopic eczema is more common in children, often developing before their first birthday. It's usually a long-term condition, although it can improve significantly, or even clear completely, in some children as they get older. Atopic dermatitis is a type of eczema and often occurs in infants with allergies to allergens like cow’s milk.2,25

Elemental formula.

See amino acid-based formula.

Elimination diet.

The process of excluding certain food which may be causing your symptoms from your diet, like cow’s milk, from a diet to determine whether it is responsible for causing allergic reactions for two to six weeks. Breastfeeding mums may eliminate milk products from their own diets to determine whether a baby has cow’s milk allergy. Formula fed babies may switch to a hypoallergenic formula, which means it has been specially designed to not cause allergic reactions in babies with cow’s milk allergy. Never restrict your baby’s diet unless this has been advised by a healthcare professional.13,14


A type of disease-fighting white blood cells that are involved in inflammatory processes like allergic disorders. When too many eosinophils congregate where they would not be usually present they can cause chronic inflammation, resulting in tissue damage.26

Eosinophilic oesophagitis (EoE).

Sometimes described as oesophageal asthma, EoE is an allergic condition caused by inflammation of the oesophagus, which is the tube that sends food from the throat to the stomach. This occurs when eosinophils which are white blood cells move from the digestive tract, where they are supposed to stay, to the oesophagus and build up, causing inflammation and discomfort.26

Essential fatty acids.

A group of fatty acids that are essential to human health and cannot be manufactured by the body, so you must get it from your diet. Essential fatty acids are also abbreviated as EFA.27

Extensively hydrolysed formula (eHF).

A hypoallergenic formula for infants containing a thoroughly broken—down form of protein, so that the immune system of most infants would no longer be able to recognise it as harmful.28



Also known as 2’-FL, 2’-fucosyllactose is the most common form of human milk oligosaccharide in mothers’ milk, which has been clinically shown to help support a baby’s developing immune system.29-32


The expel of intestinal wind that forms while food is being digested and when swallowing air. The air is then passed through the rectum. Flatulence is a normal process, but can sometimes by a sign of a health condition. When gas gets trapped you may notice your baby’s belly appear bloated or have a hard tummy and you may also notice them cry or become more fussy than usual.33

Food allergy.

A condition that causes an allergic reaction to substances found in food or drink, such as cow’s milk protein. An infant with a food allergy to cow’s milk may show colic, hives, itchy rash, swelling of the face, wheeze, vomiting, diarrhoea and refusal of food.3

Food challenge.

See oral food challenge.

Food intolerance.

A condition that causes difficulty digesting certain food and having an unpleasant physical reaction to them. Food intolerance may also be referred to as non-IgE-mediated food hypersensitivity or non-allergic food hypersensitivity. The difference between a food allergy and food intolerance is that food allergies typically cause an immune response, while with food intolerance the reaction is triggered by your digestive system.3

Food protein enterocolitis syndrome.

A condition causing vomiting, abdominal pain and diarrhoea. Food Protein-Induced Enterocolitis Syndrome or FPIES, is a delayed (non-IgE-mediated) food allergy. It most commonly affects babies and infants and will show symptoms 30 minutes to 6 hours after eating the problem food, it may cause infants to also become lethargic and sleepy.34

Food sensitisation.

The production of IgE antibodies in response to the presence of food allergens, without displaying symptoms of an allergic reaction.3



A doctor specialised in diagnosing and treating problems related to the digestive system.35

Gastroesophageal reflux disease (GORD).

For babies, spitting up (reflux) is normal and as your baby’s upper digestive tract matures, this will disappear. However, if your baby seems to be distressed or in pain as well as spitting-up frequently, this may be a sign of GORD. GORD is caused by a combination of factors which may include a weakened sphincter, which is the ring of muscle at the base of the oesophagus that connects the mouth to the stomach, or can also be linked to cow’s milk allergy.36


Hay fever.

A condition in which the immune system reacts to allergens such as pollen or dust mites, typically when it comes into contact with your nose or eyes. Symptoms include runny nose, itchy throat, sneezing, blocked nose and sore eyes. In Ireland, symptoms tend to be worse between March and October, when there is more pollen in the air.37


A rash of raised, often itchy, red welts on the surface of the skin that can appear as a result of the body’s reaction to certain allergens such as cow’s milk proteins. Hives, also known as urticaria, occur when something causes high levels of histamine and other chemicals to be released in the skin.38

Human milk oligosaccharide (HMO).

A type of complex carbohydrates found in human milk that supports infant’s developing immune system. They comprise the third largest solid component of human milk after lactose and fat and more than 100 oligosaccharides have so far been identified. The amount and composition of HMO in most mothers’ milk will vary between women and over the course of lactation.30,39


The process of breaking down a protein into smaller parts or fragments. Cow’s milk protein in extensively hydrolysed formulas for infants, has been broken down into small pieces so they are less likely to cause allergic reactions in most infants with cow’s milk allergy.28


Unlikely to cause an allergic reaction.40

Hypoallergenic formula.

Hypoallergenic formulas are recommended by healthcare professionals to infants who are allergic to cow’s milk protein. The proteins in hypoallergenic formula are so thoroughly broken down that the immune system of most babies with CMA cannot recognise and react to them.28,40



Reactions that involve the antibody immunoglobulin E, also known as IgE. IgE-mediated food allergies cause your child’s immune system to react abnormally when exposed to allergens such as milk. Infants with this type of food allergy will react quickly, usually within minutes to a few hours after ingesting food or drink containing cow’s milk.41

Immune response.

Immune response. The way in which the body reacts and defends itself to substances that appear foreign and harmful. The response is originated by the immune system. Cow’s milk protein, although often harmless triggers an immune response in babies with cow’s milk allergy.42

Immune system.

The immune system is the body's defence against infections. Cow’s milk allergy is an abnormal response by the body's immune system to milk and products containing milk.43

Immunoglobulin E (IgE).

A type of protein in the body called an antibody. As part of the immune system, it plays a role in allergic reactions, when a person is allergic to cow’s milk, this triggers the immune system and IgE is produced to fight the allergen. This starts a chain of events leading to allergy symptoms.42,43


A clinician or scientist who is trained in managing problems related to the immune system.44


Inflammation is one way the body can react to an allergen, infection, injury, or other medical condition. Symptoms of inflammation include, redness, swelling, pain, warmth and trouble using the area. Inflammation is often the unifying mechanism underlying all the conditions associated with cow’s milk allergy.45,46

Iron-deficiency anaemia.

A condition in which the blood lacks adequate healthy red blood cells, which are responsible for carrying oxygen to the body’s tissues. Red blood cells need iron to carry out their job properly. When iron levels are low, there’s a decrease in the flow of oxygen to organs and tissues in the body.47



A sugar naturally found in milk and other food made from milk.48

Lactose-free formula.

Formulas for infants and young children who find it difficult to digest lactose (lactose intolerance). These formulas are free from lactose sugar, but not from cow’s milk protein, so infants with cow’s milk allergy may react to these formulas.28

Lactose intolerance.

A condition caused by the inability to digest lactose, a sugar found in milk and milk products. Symptoms include, bloating, abdominal pain, diarrhoea and flatulence. Lactose intolerance is common in adults, but is rarely seen in young babies. Cow’s milk allergy and lactose intolerance are not the same but they are often confused with each other as they share some of the same signs and symptoms. Typically, infants with lactose intolerance can tolerate a small amount of milk and milk products and the symptoms are generally localised to the gastrointestinal tract, whereas infants with cow’s milk allergy can trigger an immune response with a small amount of milk and have more varied symptoms across the body as cow’s milk allergy involves the immune system.45,48


Milk protein.

See cow’s milk protein.

Milk sugar.

See lactose.


Necrotising enterocolitis.

Inflammation of the bowel (intestines) that may damage small or large parts of the bowel to a variable extent. It usually causes a temporary intolerance to milk-containing feeds, but in the worst cases the bowel may become so damaged that parts require surgical removal. Symptoms tend to include general signs of illness, problems feeding or vomiting, and a swollen and tender abdomen.49


A type of reaction to an allergen such as milk, that are caused by a reaction involving other components of the immune system apart from IgE antibodies. Typically, symptoms tend to appear slower compared to IgE-mediated reactions, taking from several hours to days after ingesting milk or milk products.45



The muscular tube, sometimes called the gullet or food pipe, connecting the throat with the stomach.50

Oral food challenge.

A test used to diagnose food allergies. The process involves feeding a patient a very small amount of a possible allergen (such as cow’s milk) and monitoring for any signs of allergic reactions. An oral food challenge must never be undertaken without the advice of a healthcare professional.14,24


Partially hydrolysed formula.

An infant formula comprised of partly broken down protein. Unfortunately, most babies allergic to cow's milk will react to these large pieces of milk protein. So, these formulas are not given to infants allergic to cow's milk.28


A protein is a nutrient that is formed of long chains of amino acids, which are essential for growth and repair of the body and maintenance of good health. It is also an important energy source.51



See eczema or hives.


See gastroesophageal reflux (GOR).


An inflammation of the mucous membrane that lines the nose, often due to an allergy to pollen, dust or other airborne substances.2



A process by which a person’s immune system responds to its first exposure to an allergen. This leads to the production of a defensive protein known as an antibody in response to any substance it considers a threat. In some, but not all cases of sensitisation, the production of the antibody leads to symptoms of allergy when that substance or food is encountered.2

Short bowel syndrome.

A condition that occurs when fluids and nutrients are not absorbed by the gut like they should. This is often because part of the small intestine is missing or isn’t working right. Short bowel syndrome can be present from birth (congenital) or can result from damage to the intestine by various conditions such as necrotising enterocolitis.52

Skin prick test.

A common allergy test for IgE reactions to allergens. A skin prick test for cow’s milk allergy involves exposing a small area of your baby’s arm or back to cow’s milk protein, and then gently pricking the skin so the liquid is absorbed. If your baby is sensitised, the site will turn red or swell in about 20 minutes. The test should be prescribed and performed by a healthcare professional.12-14

Soy-based formula.

An infant formula made from soya beans. Soya should not be given to infants under 6 months, due to the risk that infants with CMA may develop allergy to soya.53,54



See hives



The forceful emptying of the contents of the stomach, also commonly known as throwing up. It is normal for nausea (upset stomach) to come before a bout of vomiting. Vomiting can occur for a multitude of reasons, one being an allergy to cow’s milk protein.55



A high-pitched whistling or rattling sound heard more clearly when you exhale that often indicates a person is having problems breathing perhaps due to an allergic reaction.43


A protein found in cow’s milk that can trigger an allergic reaction in infants with cow’s milk allergy.15,16


IMPORTANT NOTICE: Breastfeeding is best for infants and is recommended for as long as possible during infancy. Alimentum and EleCare are infant formulas for special medical purposes and should only be used under the recommendation or guidance of a healthcare professional.


UK-SIMILAC-2000018 November 2020