A Note On Lactose- It's Not Always An Allergy!

If It's Not An Allergy, What Could It Be?

Many healthy, thriving breastfed & bottle fed babies develop gastric symptoms, such as; excessive gas and frequent, watery bowel movements (only when associated with other symptoms) due to lactose overload, which is associated with large, frequent feeds. These symptoms cause tummy pains. A baby with tummy pain can appear to be hungry because he seeks to feed in an attempt to relieve this discomfort, (which it does but only temporarily). However, the extra feedings could further add to the vicious cycle of lactose overload and gastric symptoms.  Lactose overload - also called 'functional lactase insufficiency' - is a common but poorly recognized problem affecting countless numbers of breastfed and bottle-fed babies in the early months of life. The number of babies affected is unknown owing to the transient nature of the symptoms associated with this problem. The distress experienced by babies suffering GI discomfort due to lactose overload is typically dismissed as ‘its normal’ or misdiagnosed as colic, reflux, lactose intolerance, or milk protein allergy or intolerance.

When Does It Affect Babies Most?

Newborn babies are very susceptible to lactose overload due to their involuntary sucking reflex which disappears around 3-4 months old. It is triggered by pressure on the baby’s hard palate by the mother’s nipple, the nipple of a feeding bottle, a pacifier, the baby’s fist, or a parent’s finger. Once the sucking reflex has been triggered, the baby will suck regardless of whether she is hungry or not. Because a reflex is an involuntary, automatic response, she cannot not suck. The presence of a baby's sucking reflex increases the risk of overfeeding if parents are not careful, especially in the case of bottle-fed babies.

What Causes Lactose Overload?

Baby’s are designed to digest lactose, many cannot digest excessive amounts.  Larger amounts of milk that travel thru the intestinal tract will be pushed thru quicker, and unable to be digested properly.  It is the amount of milk that is in the intestines at any given time that causes the problem.  

As milk begins to drain from the small intestines this stimulates the gastro-colic reflex. This reflex causes contractions of the intestinal wall, which then pushes the contents along. It’s the body’s way of making room for the new feed. (The gastro-colic reflex action is why newborn babies often poop or pass gas during feeding and grunt at times.) If a baby is fed again before the lactose in the previous feed is fully digested, the gastro-colic reflex may push some of the undigested lactose from the previous feed from the small intestines through to the large intestine

Once there are undigested lactose in the large intestine, this is when the trouble starts.  Undigested lactose will draw in excess water from the intestine walls thru a process called osmosis.  Then the intestinal bacteria will begin to ferment the undigested lactose. The end result for baby is bloating, intestinal cramps, frequent watery/sloppy, foul smelling bowel motions, and lots of farts. Stools are acidic and can scald baby’s little bottom if left in contact with the skin too long.

Once your baby starts to feel pain, she will cry out for a bottle for comfort.  When this happens, the baby is consuming again too much milk & lactose so the cycle will repeat itself again.  


  • A formula-fed baby’s bowel motions tend to be sloppy and foul smelling.
  • Bloating
  • Cramps
  • Excessive gas (farting) - foul smelling.
  • Irritability/screaming.
  • Sleeplessness or wakefulness.
  • Baby appears to be constantly hungry.
  • Baby gains large amounts of weight (which is not the case when a baby is lactose intolerant).
  • Baby is usually less than 3 months old, but in some cases this problem can continue up to the age of 5-6 months.
  • The baby might also spit up or regurgitate milk (not due to lactose overload but rather overfeeding which causes
  • symptoms of lactose overload).
  • Fussing during the feed and bearing down.
  • Extreme grunting in early hours of the morning.

Lactose Allergy Vs. Lactose Overlaod

The GI symptoms associated with lactose overload and lactose intolerance are due to the fermentation of undigested lactose in the large bowel.  Hence, the GI symptoms for both problems are the same. A baby troubled by lactose overload will have false positive results when tested for lactose intolerance.  These tests check the baby’s stools (poop) for indications of acid, which is present when lactose is fermented in the large bowel (which will occur with both problems).  

In the case of lactose overload, it’s the excess lactose, beyond what is normal, that the baby has trouble digesting.  Although irritable due to GI discomfort, the baby is physically well and gaining weight well.  [Rarely, a breastfed baby might display poor growth as a result of this problem.]

In the case of lactose intolerance, the baby is unable to digest normal amounts of lactose.  This means the baby, whose main or only source of nutrition is milk, will be deprived of the calories that lactose provides (while she is fed milk containing lactose).  She will quickly become unwell and lose weight.  

Why Lactose Is Import For Babies

Lactose aids in the absorption of calcium and phosphorus and supports the growth of good bacteria in the intestinal tract. (Good bacteria are a major player for prevention of bacteria & disease).  

Galactose, a simple sugar that comes from the breakdown of lactose, is vital to a healthy brain and nerve tissues. Galactose can be found is some foods, but milk containing lactose will be a baby’s only source of galactose during the early months - an important time of rapid brain growth and development.  

Glucose, the other simple sugar that bonds with galactose to form lactose in milk. Glucose is essential for energy, growth and cell development. Without glucose in the diet a baby will use body fat as a source of energy, and lose weight. A baby will not survive if deprived of glucose for a long period. Most foods, including lactose-free milk, will be broken down or converted into glucose in the body.

Preventing Lactose Overload:  

  • Use a slow flow nipple for the entire duration of the first year
  • Do not feed little & often.  Feed as your baby requires and allow adequate time between feedings.  Estimate how much formula your baby needs
  • Try to encourage your baby to go 3-4 hours between feedings during the day
  • If your baby is drinking a bottle in under 10 minutes, use a slow flow nipple & take frequent breaks
  • Allow your baby to be done with her feed when she signals, do not encourage her to keep drinking
  • Learn your babies feed cues vs sucking needs

Babies who are no longer experiencing lactose overload will have less frequent stools & sleep better.  Making adjustments to the way you feed your baby will be the ultimate best thing you can do for her.  Try these things before assuming your baby is lactose intolerant.  The better formulas for your baby will be non-hypoallergenic types, but ones made with simple ingredients.  Remember, babies have a desire & reflex to suck!  Don't get this confused by hunger.  As always, always speak to your pediatrician if you have concerns.