Condition

What is it?

Symptoms

Problem foods

Ages affected

Treatment

How common?

Late-onset lactose intolerance (also called “acquired” or “adult” lactose intolerance)

As we reach weaning age, many of us produce less lactase

Gastrointestinal discomfort, bloating, nausea, diarrhea

Liquid milk, large quantities of some other dairy foods. Cheeses, butter, baked goods not a problem.

Older kids and adults. Usually doesn’t show up until 4 or 5, almost never before 2.

Avoid foods that cause discomfort, drink lactose-free milk, or take a lactase supplement with dairy foods.

Up to 75% of the world, mostly non-Caucasians, past weaning age. Doesn’t affect infants at all.

Secondary lactose intolerance

Viral illnesses, chronic conditions like Celiac disease or milk protein allergies can all temporarily destroy lactase-producing cells on the lining of the gut

Gastrointestinal discomfort, bloating, nausea, diarrhea, green frothy poops, diaper rash

Liquid milk, large quantities of some other dairy foods. Cheeses, butter, baked goods not a problem.

Any age, for a couple weeks post illness or as long as milk allergy reaction is happening.

Explore possibility of milk allergy (see below) or chronic conditions. After a regular illness, continue breastfeeding, as it helps restore the gut. For formula-fed babies, switch to lactose-free formula for a couple weeks. For older kids and adults, avoid problem foods for a couple weeks.

Moderately common, but short-lived. Often passes unnoticed.

Congenital lactose intolerance (Confusingly, different sources use the term “primary lactose intolerance” for congenital lactose intolerance and for late-onset lactose intolerance.)

A handful of genetic disorders causing problems with digesting lactose or its constituent sugars

Failure to thrive or gain weight, lethargy

All milk or milk-based formulas

Newborns

Lactose-free formula

Very rare

Developmental lactose intolerance

The ability to secrete lactase develops in the third trimester, so very premature babies will have a hard time digesting lactose.

GI discomfort

Very premature babies

Breastmilk is important for premature babies whenever possible, and may even stimulate lactase production. Supplemental lactase can be given if needed.

Only in premature babies; common for them. Is outgrown.

Lactose overload

foremilk-hindmilk imbalance

Too much lactose-rich foremilk (or too much formula) can overwhelm a perfectly healthy level of lactase production.

Gastrointestinal discomfort, bloating, nausea, diarrhea green frothy poops, diaper rash.

None. It’s only about quantity.

Infants

One breast per feeding, or block nursing. Be careful not to overfeed with formula.

Unclear, but probably more common than we think. Lactose intolerance tests will give positive results due to undigested lactose in stool.

Milk protein allergy (antibody mediated)

The body’s immune system misidentifies milk proteins as dangerous and sets off immune reactions.

Usually some combination of hives, breathing difficulty, rashes, vomiting, runny nose, and GI discomfort. In extreme cases, anaphylactic shock. Immediate onset.

Cow and/or goat milk in any form, any amount (depending on severity of the allergy). Breastmilk if mother has been eating dairy herself.

Infants through adults, but usually goes away by school age.

Avoid cow/goat milk products. Breastfeeding mothers also avoid milk products (takes two weeks to clear out).

The most common food allergy in babies (2.5 percent). However, tests have a high false positive rate.

Milk protein allergy (GI tract)

A different class of food allergy is not mediated by an antibody and gives only GI symptoms. Can cause secondary lactose intolerance.

GI discomfort, bloating, nausea, diarrhea green frothy poops, diaper rash.

Cow and/or goat milk in any form, any amount (depending on severity of the allergy). Breastmilk if mother has been eating dairy herself.

Infants through adults, but usually goes away after first year of life.

If lactose overload has been ruled out as the culprit, avoid cow/goat milk products. Breastfeeding mothers also avoid milk products (takes two weeks to clear out).

Fairly common, but hard to diagnose, as there is no blood test or skin test.