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Formula Allergy In Babies: Causes, Signs And Treatment

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Formula or formula milk is designed to substitute human milk for babies (1).It contains nutrients to support the growth and development of an infant. Its use is recommended by several apex pediatric organizations when breast feeding isn’t possible, or breast milk supply isn’t enough to meet the baby’s dietary needs.

While most babies consume formula without much concern, some may develop formula allergy. Formula allergy is an immunological condition that causes mild to severe allergic reactions after formula milk ingestion. Prompt pediatric evaluation is necessary to resolve the symptoms at the earliest.

This post shares the difference between formula allergy and intolerance, causes of formula allergy, its symptoms, and treatment.

Is Formula Milk Allergy Common In Babies?

Most baby formulae use animal milk (cow) or plant milk (soy) as the protein source. According to the American Academy of Pediatrics (AAP), 80 percent of the commercial formulae are cow milk-based (2). Cow milk is a common food allergen, with cow milk protein allergy affecting about two to three percent of infants (3) (4).

According to the British Journal of General Practice, “The incidence of cow’s milk protein allergy (CMPA) in formula-fed babies is around five to seven percent (5)Besides, about 10 to 14 percent of babies allergic to cow milk exhibit reactivity to soy protein (6). Soy itself is a common allergen that can trigger an allergic reaction in babies.

What Is The Difference Between Formula Intolerance And Formula Allergy?

Formula intolerance and formula allergy are different conditions.

Formula intolerance is a non-immunological condition involving the digestive system. It is when the digestive system cannot breakdown certain formula milk compounds due to some underlying reason, leading to gastrointestinal discomfort. Food intolerances could develop due to congenital or acquired enzyme deficiencies, sensitivity to food additives, reactions to naturally occurring chemicals in foods, or accidental ingestion of a toxin/pharmacologic agent (7) (8).

Formula allergy is an immunological condition where the immune system mistakenly identifies milk proteins as pathogens and attacks them with antibodies. The immune response leads to an allergic reaction, causing symptoms such as hives (skin bumps) and tissue swelling. Allergies are usually more severe and life-threatening than food intolerances.

What Causes Formula Allergy In Infants?

The hypersensitivity and inappropriate action of the immune system towards formula lead to formula allergy. The immune system identifies one or more proteins in the formula milk as foreign entities or pathogens and attacks them. It ultimately triggers allergic reactions, the severity of which varies from one baby to another (9).

Heredity and environmental factors may play a role in the manifestation of baby formula allergy. For instance, the chances of a food allergy rise to about 75 percent if both parents have allergies (10). The baby may also have cross-reactivity where they could display hypersensitivity to other similar substances. For instance, a baby allergic to cow milk formula may also be allergic to goat milk formula.

Signs And Symptoms Of Formula Allergy In Babies

Formula allergy can be IgE or non-IgE mediated, wherein the signs and symptoms could appear immediately or hours and even days after ingesting the formula. Here are some signs and symptoms you should keep a check on (4) (6).

  • Itchy red bumps or skin rashes (hives)
  • Acute wheezing, blocked or runny nose
  • Acute vomiting
  • Swelling of the mouth, cheeks, lips, tongue, and throat
  • Abdominal cramps, diarrhea (possibly bloody), or constipation
  • Loss of appetite
  • Slow weight gain
  • Extreme irritability or colic

In some cases, formula allergy can cause a potentially severe allergic reaction (anaphylaxis), making the prompt diagnosis of the condition imperative.

Diagnosis Of Formula Allergy

There is no specific test to detect formula allergy. If you suspect your baby has formula allergy, consult a pediatrician promptly.

  1. Physical examination: During the physical examination, the doctor will collect the baby’s medical history, family medical history, and details about symptoms. The doctor may suggest an elimination test based on the information collected.
  1. Elimination diet test: In this test, your doctor will ask you to eliminate the current formula milk from your infant’s diet and reintroduce it after a week. If reintroduction causes a reaction, it indicates formula allergy. Your pediatrician may recommend additional tests to confirm the
  1. Blood test: A blood test for formula allergy will estimate the number of antibodies present in the body. These antibodies are responsible for triggering an allergic reaction. Additionally, the doctor may ask for a stool test to help determine inflammation in the body, generally seen in milk allergy (11).
  1. Skin prick test: This test involves placing drops of formula milk on the back of the infant’s hand or forearm. The skin is then pricked using a sterile probe to let the milk enter the skin. If an itchy, reddish bump develops within 15 to 20 minutes, it indicates an allergy. This test is rarely conducted in babies younger than six months (12).

Based on the diagnosis, your doctor will suggest switching to a different baby formula and seeing how the baby reacts. The next section contains some baby formulas that could be advised to a baby with formula allergy.

Can Formula Allergy Be Treated?

There is no cure or treatment for formula allergy. An infant with formula allergy is advised to use hypoallergenic formula. Below are some commercial formulae that your doctor could recommend, depending on your infant’s symptoms and tolerance  (5) (13).

1. Soy infant formula

Soy infant formula is made of soy protein isolate and is free from cow milk protein and lactose (14). Its use is often advised to babies with lactose intolerance. Some babies with cow milk allergy may develop soy protein allergy. However, term infants with IgE-mediated allergic reaction to cow milk protein may use soy-based formula (15).

2. Hydrolyzed protein formula

These are hypoallergenic formulas available in two types —partially hydrolyzed and extensively hydrolyzed.

  • Partially hydrolyzed protein formula contains cow milk protein (whey and casein) broken down into smaller proteins that are easy to digest. However, the hydrolysis is not enough to render the protein inactive to trigger an allergic reaction. Thus, this formula is not suitable for babies with cow’s milk allergy but may be beneficial to babies with a soy allergy.
  • Extensively hydrolyzed protein formula contains casein that is broken down into smaller, easy-to-digest form. About 90% of babies with cow’s milk allergy can tolerate this formula as it is easy to digest and does not trigger an allergy. Casein is the most common cause of cow milk allergy in babies.

3. Amino acid-based formula

Amino acid-based formula or elemental formula contains amino acids, which are the basic building blocks of proteins. This formula is well-tolerated by most babies. It is typically recommended for babies who are unable to tolerate even extensively hydrolyzed formula.

The USDA advises parents and caregivers not to change a baby’s formula without consulting a pediatrician. Speak to a pediatrician if you wish to try another type of formula for your baby with formula allergy.

Formula allergy in babies can happen if an infant is allergic to cow milk or soy. If you suspect your baby has formula allergy, consult a pediatrician promptly. The doctor can help diagnose the symptoms correctly and suggest appropriate formula alternatives for your baby.

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