FPIES in babies: signs, triggers and what to do

What FPIES is

FPIES stands for food protein-induced enterocolitis syndrome. It’s a type of food allergy that affects the gut, and it mostly shows up in babies and young children.

It isn’t the same as the more familiar kind of food allergy. Most food allergies involve an antibody called IgE and cause quick reactions like hives or swelling. FPIES is a non-IgE allergy: the reaction is delayed, and it centers on the stomach and gut.

FPIES is not common, and most babies who vomit after a new food have a stomach bug or a one-off upset. But knowing the pattern helps you spot it, because it’s often mistaken for a stomach virus or an infection at first.

Signs of an FPIES reaction

The typical pattern, described in the international guidelines, is:

• repeated vomiting that starts about 1 to 4 hours after eating the trigger food, often many times
• a baby who looks pale, floppy or unusually tired or sleepy
• sometimes diarrhea, usually starting later (around 5 to 10 hours after eating)
• usually no hives, lip swelling, wheezing or other skin and breathing signs

A reaction usually settles within a day, and the baby is well between reactions. Because the vomiting is delayed, the link to the food isn’t always obvious.

There is also a slower form, mostly in young babies on cow’s milk or soy formula: ongoing vomiting, diarrhea and poor weight gain that get better once the food is stopped.

When to get urgent help

Severe FPIES reactions can cause dehydration and a drop in blood pressure, and some babies need treatment in hospital with fluids through a drip.

Call 911 or go to the emergency room if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake.Call 999 or go to A&E if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake.Call your local emergency number (such as 112 in Europe or 000 in Australia) or go to the emergency department if your baby is vomiting again and again, or is pale, floppy, very sleepy or hard to wake.

Tell the team you think it may be FPIES, and what your baby ate and when.

If your baby has vomited only once or twice and seems alert and like themselves, offer breast milk or small sips of fluid (not a formula you think may be the trigger), watch them closely, and call your pediatrician or GP for advice. Get help straight away if the vomiting continues or they become floppy or drowsy. If your baby has already been diagnosed with FPIES and had a severe reaction before, follow the emergency plan from their allergy team, which may mean going to hospital straight away even if they seem well.

FPIES is different from anaphylaxis. Epinephrine (adrenaline) is the emergency medicine for anaphylaxis, but it isn’t the usual treatment for FPIES because it doesn’t stop the vomiting. If your baby has hives, swelling or trouble breathing, treat it as a possible severe allergic reaction: see signs of anaphylaxis.

Common trigger foods

Any food can cause FPIES, but some are much more common. ACAAI lists:

• cow’s milk and soy, especially in infant formula
• grains such as rice, oats and barley
• chicken, turkey and fish

Egg is a less common trigger in most countries, though it’s the third most common in Australia. Egg FPIES is different from the immediate kind of egg allergy covered in egg allergy. Many children with FPIES react to only one food, most often cow’s milk. Rice is the most common solid food trigger in most countries studied.

Many of these, like rice and oats, aren’t foods people usually think of as allergens. That’s one reason FPIES is often missed. FPIES in exclusively breastfed babies is very rare.

How it’s diagnosed

There’s no skin prick or blood test for FPIES. Standard allergy tests are usually negative, because FPIES doesn’t involve IgE.

An allergist makes the diagnosis from the pattern of symptoms: what your baby ate, how long before the vomiting started, and whether it happened again with the same food. Sometimes they’ll suggest a supervised food challenge in clinic, where your baby eats a small amount of the food with medical help on hand.

If you suspect FPIES, write down what your baby ate, the time they ate it, and when the vomiting started. Bring the notes to the appointment.

Living with FPIES

Avoid the trigger food completely, as your allergist advises. Don’t try it again at home to “check”: the guidelines advise reintroducing an FPIES trigger only under medical supervision, because reactions can be severe.

Keep offering other foods. FPIES is not a reason to stop starting solids. Avoiding foods your baby doesn’t react to can lead to a limited diet and feeding problems later. Your allergist or a dietitian can help you plan which foods to try next and in what order. They may suggest:

• offering one new food at a time, with a few days between new foods
• starting with foods the consensus guidelines rate as lower risk, such as broccoli and avocado
• taking extra care with foods the guidelines rate as higher risk: iron-fortified infant rice and oat cereals, milk, soy, poultry, egg and fish such as salmon

If one food in a group goes well (for example, one type of bean), other foods in the same group are more likely to be fine too.

If your baby has milk or soy FPIES, the guidelines encourage breastfeeding or a hypoallergenic formula, such as an extensively hydrolyzed formula, chosen with your doctor. See cow’s milk allergy for more on formulas.

Will my baby outgrow it?

Usually, yes. ACAAI says most children outgrow FPIES by age 3 or 4, though it can take longer for some foods, such as rice and oats. Your allergist will check from time to time, often with a supervised food challenge, to see whether your child can eat the food again.

FPIES and other allergens

Having FPIES doesn’t mean holding back the common allergens like peanut and egg for no reason. Delaying them may make a typical IgE allergy more likely. Ask your allergist how and when to introduce each one alongside your baby’s FPIES plan. For the general approach, see how to introduce allergens.