Casein is a protein found in milk and other dairy products. A casein allergy occurs when your body mistakenly identifies casein as a threat to your body. Your body then triggers a reaction in an attempt to fight it off.
This is different than lactose intolerance, which occurs when your body doesn’t make enough of the enzyme lactase. Lactose intolerance can make you feel uncomfortable after consuming dairy. However, a casein allergy can cause:
- severe pain
- food malabsorption
- breathing problems
Casein allergies are most common in infants and young children. This allergy occurs when the immune system mistakes casein as something the body needs to fight off. This triggers an allergic reaction. Infants who are breast-fed are at a lower risk of developing a casein allergy. Experts aren’t completely sure why some infants develop a casein allergy while others don’t, but they believe genetics may play a role.
Usually, a casein allergy will go away by the time a child reaches 3 to 5 years of age. Some children never outgrow their casein allergy and may have it into adulthood.
Where is casein found?
Mammal’s milk, such as cow’s milk, is made up of:
- lactose, or milk sugar
- up to four kinds of casein protein
- other kinds of milk proteins
The amount of each of these substances in milk depends on:
- which animal the milk comes from
- where in the milking cycle the animal was
- how long the animal has been lactating
- what the lactating animal was eating
Many dairy products contain casein, but not all do. Because casein is a protein, it’s found mostly in dairy products with moderate-to-high protein content such as:
- low-fat milk
- ice cream
Dairy products containing less protein and more fat, such as butter and cream, contain very little casein. Clarified butter, or ghee, contains no casein at all.
Casein can also be in other foods and products that contain milk or milk powder, such as crackers and cookies. This makes casein one of the more difficult allergens to avoid. This means it’s very important for you to read food labels carefully and ask what’s in certain foods before buying or eating it. At restaurants, make sure you alert your server about your casein allergy before ordering food.
You should avoid products that contain milk or may have been exposed to foods containing milk if you or your child has a casein allergy. A food’s ingredients list will state this. Additionally, some food packaging may voluntarily list statements such as “may contain milk” or “made in a facility with milk.” You should avoid these foods as well because they may contain traces of casein.
One in every 13 children under 18 years of age has food allergies. A casein allergy will typically show up when an infant reaches 3 months of age and will resolve by the time the child is 3 to 5 years old. It’s not known exactly why this occurs. However, researchers have found that some children with casein allergies who are exposed to small amounts of casein in their diets appear to outgrow their allergies more quickly than children who consume no casein.
The American Academy of Pediatrics (AAP) recommends that children not be introduced to cow's milk before 1 year of age because a baby’s body cannot tolerate the high levels of protein and other nutrients found in cow’s milk. The AAP suggests all babies be fed only breast milk or formula until 6 months of age, when you can begin introducing solid foods. At that point, avoid feeding your child foods containing milk, and continue giving them only breast milk or formula.
You should call your doctor right away if your child is showing any of the symptoms of a casein allergy. They’ll ask you about your family’s history of food allergies and will perform a physical exam. There isn’t a specific test that will diagnose a casein allergy, so your child’s doctor will perform several tests to make sure another health problem isn’t causing the symptoms. These include:
- stool tests to check for digestive problems
- blood tests to check for underlying health issues
- a skin prick allergy test in which your child’s skin is pricked with a needle containing a small amount of casein to see if a reaction occurs
Your child’s doctor may also give your child milk and observe them for several hours afterward to look for any allergic reaction.
There are many substitutes for casein-based products on the market, including:
- soy, rice, or potato-based milks
- sorbets and Italian ices
- certain brands of soy-based products, such as Tofutti
- certain brands of creams and creamers
- most soy ice creams
- coconut butter
- certain brands of soup
In recipes calling for 1 cup of milk, you can substitute 1 cup of soy, rice, or coconut milk or 1 cup of water combined with 1 egg yolk. You can use the following to replace dairy yogurt:
- soy yogurt
- soy sour cream
- pureed fruit
- unsweetened applesauce
Currently, no definitive link between a casein-free diet and a reduction of disease or disorder symptoms has been established. Studies are ongoing, and some people have found that cutting out casein improves the symptoms of some health problems. If you’re considering a casein-free diet, it’s important to consult with your doctor first.