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Infant Food Allergy Reaction Timing: When They Start & What To Look For

No matter what type of food allergy reaction your baby has, it’s terrifying. Whether it’s trouble breathing or a nasty rash, you want to be prepared.

Free To Feed’s your infant food allergy support system — here to educate, provide resources, and give you confidence on your food allergy path.

How long reactions last can become a revolving door. You think you’ve hit baseline and bam — another reaction. Or you realize you consumed a hidden allergen, grr. It’s hard to nail down triggers with food allergy symptoms, and reaction times only add to the confusion.

Today we’re diving deeper into when allergic reactions occur, how long they last (depending on what’s affected), and how you’re never alone with Free To Feed.

The Most Life-Threatening Allergic Reaction? Anaphylaxis!

Did you think of someone reacting horribly to peanuts or latex, like they show in the movies? The person will likely look like they can’t breathe and someone’s quickly coming to the rescue.

When a baby can’t breathe after consuming an allergen, that’s 1 critical body system failing (lungs). But that doesn’t happen nearly as often as you’d think.

If 2 non-critical body systems fail (skin and stomach), it’s considered anaphylaxis! Hives and vomiting are the most common anaphylaxis reactions in babies.[1]

This reaction’s the most life-threatening allergic response and can lead to death. Hard to even put into words when it comes to your child, and we want to do everything possible to prevent this trauma for your family.

Anaphylaxis happens so fast because the body’s immune response creates a burst of IgE antibodies that often affect multiple areas of the body at the same time (lungs, GI tract, skin, etc).

Anaphylaxis usually occurs within 5-30 minutes after exposure — but can take up to 1 hour.[2]

Warning signs include:

  • Red rash

  • Hives/welts that itch

  • Swollen throat

  • Trouble breathing

  • Passing out

  • Vomiting

  • Pale or red color to the face

Get immediate medical attention, and work closely with your child’s allergist or immunologist. If your child has an IgE allergy, we hope you’ve been shown how to use the life-saving epi-pen. (Thank you, medical science!)

Most babies that experience an anaphylactic reaction, and get the medical attention they need, are very sleepy after it’s all over. Their little bodies went through a lot, so don't be surprised if they need more snuggles that day or night. (We know you will too!) Let’s look into other food allergy responses to watch out for.

How Long Skin Reactions Last For A Food Allergy Baby

Research suggests that up to 40% of children with eczema and skin conditions could be experiencing a reaction from food allergies.[3] Battling skin ailments like eczema can feel like a spinning wheel — it gets better and then worse. Better again, then way worse. It’s beyond frustrating and makes it harder to find the source.

Skin reactions (not hives) from food allergies are often delayed up to 4-6 hours after exposure. [3] Research indicates that skin flares for some take up to two days for it to peak.

Leaving you scratching your head — from six hours ago… *squints eyes*

Laundry detergent?

New lotion?

Different brand of seasoning?

We know it’s discouraging but finding the cause gets your baby to baseline fastest. Our consults get specific with your family’s unique case and feeding goals. We know everyone has different needs.

The good part? Usually, skin begins to heal within 48 hours — after removing the confirmed allergen from the diet.

Your baby’s ultra-sensitive skin needs tons of extra moisture! Read more from us about eczema in pictures here and treatments for home here. Next, let’s travel into the delicate digestive tract of our food allergy babies.

Infant Food Allergy Gastrointestinal (GI) Responses Vary

AKA, when will you get back to a good poopy diaper from your baby? When dealing with digestive issues, it’s tough because you can’t do something right away to make it better, like put lotion on it. You feel helpless. You might find yourself even more confused too, because the long winding digestive tract makes it difficult to pinpoint triggers.

It’s true that some mucus isn’t a cause for concern. But after 5 years of helping families, our threshold is different’s compared to others because we back it with published research. We’re certain of the detrimental impact food allergies cause to digestive symptoms. There’s a specific category for non-IgE-mediated food allergies concerning the GI tract.

Dropping some science terms now…

Food protein-induced allergic proctocolitis (FPIAP)

Often occurs 6-8 hours after ingestion, but can take up to 48 hours or longer depending on stool frequency. (Talk about confusing.)

Food protein-induced enteropathy (FPE)

Same as FPIAP. Sometimes initial discomfort can be seen sooner since FPE occurs in the small intestine.

Food protein-induced enterocolitis syndrome (FPIES)

FPIES can be a tricky issue to navigate because it can be an acute and/or chronic reaction, often the first response to the food occurs after more than one introduction, and the most common triggers include seemingly benign foods such as rice, oats, sweet potato, avocado, banana, and more. Dr. Trill's second daughter had FPIES and offers a full research deep dive in our Flourishing with FPIES Mini-Course.

Acute (happens fast and heals fast): Typically, acute symptoms like vomiting or reflux begin immediately or up to a few hours after exposure.

Chronic (happens slowly and heals slowly): These types of responses occur in the intestinal system and follow the same timeline as FPIAP.

How long will GI symptoms last?

It truly depends on each child’s sensitivity levels and how much of the offending food allergen they had. We wish we had a better answer but we don’t. We’ve seen it all, and you’re not alone on this difficult journey.

Most GI issues with food allergies are outgrown with time — a relief for you to know. The medical field calls this a “favorable diagnosis” and we couldn't agree more, but we understand it’s still a tough hill to climb when you’re doing it.

This is one reason baby food allergies can be confused with “intolerances,” simply because they’re outgrown. You can read more on this confusing topic here.

Are You Wondering When The Crying Will Stop?

If you didn’t know yet, we simply don’t believe colic to be a diagnosis. Our research and years of experience point to a root cause for that much discomfort in babies. And if there is a root cause, that means colic is a symptom instead of a diagnosis!

When you effectively remove the correct food trigger(s) at the same time, you should see SOME type of improvement within 4-5 days.

Correct, not weeks. If that just made you stop, make sure to read our page on breastmilk transferability here. Hold onto hope. We know days can feel like years during a flare-up or reaction.

Let Us Be Your Food Allergy Support System

Reaching baseline is key. And we understand how it feels to not have your concerns be heard. Keep advocating for your baby and trust your gut. You know your baby best — don't forget it!

From the start, our mission’s been to reduce your baby’s awful symptoms fast and get your family on the road to healing. Don’t spend hours on Google or stressing when you have food allergy experts fighting in your corner.

Choose from our team of food allergy expert MOMS to support your experience! All our compassionate professionals come prepared with empathy and direction for your family's unique needs.

Get ultimate guidance with our 3 MONTH Food Allergy Support Package. Don’t stress about meals, elimination diets, reintroduction steps, or anything with us behind you.

Being a parent to a completely healthy child’s hard work, and being a parent to a food allergy baby makes you a warrior. Don’t forget how much extra effort you’re putting in for your child. You’re incredible.

We see you.



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