By Tracey Alperin, B.S.
Brigham and Women's Hospital
An allergy is an overreaction by your immune system to a substance (allergen) that is normally harmless. Common allergens are dust mite, pet dander, pollen and certain foods, such as eggs, milk, nuts and fish.
What causes an allergy to develop?
There are three risk factors for developing an allergy.
- Genetics – Allergies run in families. A child has a much higher risk of allergy when there is a family history of allergy.
- Contact with an allergen – Some evidence indicates that prenatal exposure or exposure during infancy to an allergen may make a child more sensitive to the substance. Exposure to dust mites, cigarette smoke and air pollution may increase the risk of atopic dermatitis, allergic asthma, rhinitis and food allegies.
- Bottle feeding – Breast milk has special proteins made by the mother's immune system that help protect babies from developing allergies.
Why is breastfeeding good for a baby's immune system?
Breast milk affects a baby's immune system in many ways. For instance:
- Breast milk has lymphocytes and macrophages. These are white blood cells that are active in the immune response to bacteria and viruses. Macrophages kill bacteria that bind to their surfaces. Lymphocytes make antibodies in response to bacteria and viruses. This helps the body recognize and destroy them more quickly. These antibodies from mom are very important because infants don't make antibodies efficiently until six months of age.
- Breast milk contains Lactobacillus bifidus. This harmless bacterium is naturally found in our guts and helps us digest food. As Lactobacillus bifidus breaks down food, it produces lactic acid. This makes the inside of the gut acidic and "unfriendly" to many bad bacteria.
- Nursing an infant when his mother is sick is beneficial. Mom is making antibodies to her illness. These antibodies are passed directly to her infant through her breast milk. This helps the baby fight off the virus without becoming sick.
Can breastfeeding reduce a baby's risk of developing an allergy?
There are several theories for how breastfeeding may help prevent a child from developing an allergy. For example, mom's antigens in breast milk might sensitize an infant and help her be less susceptible to an allergy.
Another proposed theory is that breast milk may act as a buffer against infectious organisms within the infant's intestine.
Whatever the explanation, the literature supports that:
- Solely breastfeeding an infant reduces the risk of asthma.
- Any amount of breastfeeding decreases the risk of recurrent wheezing.
- Breastfeeding protects against cow's milk allergy in children with a family history of allergy.
Should mom eliminate certain foods from her diet while breastfeeding in order to reduce her baby's risk of developing an allergy?
Expectant or new mothers may want to eliminate common food allergens such as eggs, cow's milk, fish and nuts from her diet. The medical literature indicates that it may reduce an infant's risk of developing an allergic disease in the first year or two of life. However, there is not enough evidence that this gives a child long-term protection from allergies.
What are some other advantages of breastfeeding?
- Breast milk provides all the nutrients your baby needs. As your baby's nutritional needs change, so does the composition of breast milk.
- Breast milk is free and readily available. No assembly required.
- Breastfeeding triggers the release of oxytocin, which helps to contract the uterus so it can return faster to its normal size.
- A breastfed baby has fewer colds, episodes of diarrhea, ear infections and gastrointestinal problems. That's because mom's antibodies has made the baby's immune system stronger.
- Breastfeeding allows time for baby and mom to bond. The oxytocin that breastfeeding releases helps mom fall in love with her baby.
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Tracey Alperin is a recent graduate of the Brigham and Women's Dietetic Internship. She completed her B.S. in Human Biology, Health, and Society from Cornell University.