How to Tell if a Baby Is Allergic to Formula

Formula intolerance is a fairly common occurrence in infants, but recognizing the signs of an allergy isn’t always easy. Learn what red flags to look for.


When my son was born back in 2007, he arrived healthy and content. As a formula-feeding mama, I choose to nourish my newborn with the brand suggested by my doctor. With a ready-to-feed formula bottle in hand, I went to work feeding my baby. He happily sucked it down.

With guests coming in and out of the hospital room along with my own cheerful, yet oblivious, disposition, I didn’t notice the subtle signs that something was amiss with my son. Fortunately, my nursing team did.

Soon after feeding he would not just spit up, but vomit large amounts of formula. Projectile vomit was more like it. He also experienced bouts of colic that occurred soon after feeding. We would soon find out that this unexplained fussiness was related to gas and abdominal pain.

After switching to a sensitive formula specifically designed for infants with cow’s milk allergy, my son’s symptoms vanished overnight. He left the hospital a day later than usual, but with the newfound ability to keep his formula down.

As approximately 80 percent of formulas currently on the market are milk-based, a cow’s milk allergy can become apparent as soon as a parent introduces their infant to formula. According to Chris Iliades, MD, up to 7.5 percent of infants develop cow’s milk allergies.

What the Experts Say

Babies may show the first symptoms of a milk allergy day to weeks after they’re first given a cow milk-based formula. Although breastfed infants are at a lower risk of developing a milk allergy, babies may show allergy symptoms if the mother has dairy in her diet.

Here is what the experts have to say about formula allergies, and what you can do to diagnose and manage symptoms.

“If your baby cries with feedings and produces occasional blood-tinged stool, he is likely to be suffering from milk protein, allergy.”

– Dr. Paula Elbirt, MD, Dr. Paula’s Good Nutrition Guide for Babies, Toddlers, and Preschoolers

“Sometimes babies’ bodies react to a particular protein or sugar in cow’s milk and you may need to experiment with different brands to find one that is the most readily digested by your baby.”

– Sandy Jones, Marcie Jones, and Michael Crocetti, Baby’s First Year

“Most commercial formulas are modified cow’s milk, and some infants have allergic reactions to them. Upset stomachs, diarrhea, irritability, and skin rashes will let you know that something isn’t quite right.”

– Editors of Good Housekeeping Magazine, The Good Housekeeping Illustrated Book of Pregnancy and Baby Care

“Detecting food allergens in the bottle-fed infant is the easiest of all elimination diets – provided the child will accept a new formula and the new formula does not also produce reactions. The easiest first attempt is a switch to soy-based formula.”

– Linda Folden Palmer, Baby Matters: What Your Doctor May Not Tell You About Caring for Your Baby

“Extensively hydrolyzed formulas (EHF) are the best alternative to milk-based formulas if the baby cannot be breastfed. In these formulas, the proteins have been broken down into constituent amino acids and peptides too small to be allergenic.”

– Janice Vickerstaff Joneja, Dealing with Food Allergies in Babies and Children

Signs Your Baby is Allergic to Formula

We’ve all heard the fundamental message ‘breast is best’. However, some women are unable to breastfeed for one reason or another. For women who are unable to or choose not to breastfeed, formula is a nutrient-rich substitution.

When introducing your baby to infant formula, be on the alert for signs of an allergy. While allergies can develop in any baby at any age, it’s more common in families where mom or dad have allergies.

In the majority of formula allergies, cow’s milk protein is to blame. If your infant has a formula allergy, certain signs and symptoms may develop soon after a feeding. Symptoms may include:

  • Fussiness: While there are a million reasons why babies fuss, digestive problems are one of the most common. According to lactation consultant Jan Barger, fussiness, crying, and obvious discomfort can occur shortly after you’ve started or finished a feeding.
  • Skin Problems: Formula allergies can show up on the skin in the form of a rash, hives, or flaky patches known as eczema. Some infants also develop a ring around the rectum that resembles diaper rash but doesn’t clear up with diaper rash cream.
  • Vomiting or Excessive Reflux: While most babies spit up during the first few months of life, excessive spit up or vomiting may be a cause for concern. If not properly managed, vomiting and excessive reflux can lead to irritability, bloating, and improper weight gain.
  • Abnormal Stools: Infants on baby formula typically have stools that differ slightly from breastfed babies. However, if your baby’s stools smell foul or are overly hard or loose, a formula allergy may be causing the abnormality. Also take note of diarrhea that persists for several days or blood in the stool.
  • Respiratory Issues: Cold symptoms do not always indicate a cold. Wheezing, chronic coughing, runny nose, and nasal congestion can also be caused by a food allergy. According to Meals that Heal for Babies and Toddlers by Eileen Behan, wheezing occurs in approximately 20 to 25 percent of infants with food allergies.

What to Do If You Suspect an Allergy

If your baby is exhibiting signs of a formula allergy, consult with your pediatrician. Many doctors will diagnose an infant based on symptoms alone, and may suggest eliminating cow’s milk protein from your infant’s diet.

Of course, your little one will still need a source of nutrition in the meantime. To nourish your baby, simply switch to a hypoallergenic formula. These sensitive formulas are specifically designed to not cause allergic reactions in infants with cow’s milk intolerances. After switching to an extensively hydrolyzed, hypoallergenic formula, the majority of babies will feel better.

Don’t worry mom and dad, your baby isn’t doomed to never enjoy a bowl of mac and cheese or an ice cream cone. According to Caring for Your Baby & Young Child by Steven P. Shelov, your child has a 50 percent chance of outgrowing a cow’s milk allergy by age one, 75 percent by age two, and 85 percent by age three to four. Cow’s milk allergies rarely last into adolescence.

It can be disheartening to learn that your newborn has a formula allergy, especially if it’s causing him discomfort. By switching to a hypoallergenic infant formula, you can eliminate allergy symptoms and ensure that your bundle of joy gets the nourishment he needs to thrive.


Brandy Dishaw

Brandy is a content specialist and proud mother of two children. She enjoys writing engaging content on parenting, children’s health, and educational topics, and has been published on websites like Modern Mom, Yahoo! Shine, and With more than a decade of experience as a writer and mom, she combines research and personal experience to provide her audience with insight to the world of parenting.

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