If you’re starting solids and you keep hearing, “Try one new food… then wait,” you’re not alone. The 3-Day Test(often called the 3-day rule for starting solids) is a simple way to introduce foods that helps you notice how your baby responds—without turning mealtimes into a science experiment.
Quick definition (featured snippet-friendly):
The 3-Day Test is a method where you offer one new single-ingredient food and then wait 3 days before introducing another new food. This makes it easier to spot possible reactions and identify which food may be causing them.
Why parents use the 3-Day Test
The main benefit is clarity. When you introduce one new food at a time, it’s easier to connect the dots if you see:
- A new rash or hives
- Vomiting or diarrhea
- Extra gassiness or unusual fussiness
- An eczema flare that seems to worsen
The CDC and the American Academy of Pediatrics describe this same approach: start with single-ingredient foods and wait about 3–5 days between new foods so you can watch for reactions.
How to do the 3-Day Test (step-by-step)
- Choose one new, single-ingredient foodExamples: mashed avocado, plain yogurt, pureed carrot (texture should be age-appropriate).
- Day 1: offer a small amountThink 1–2 teaspoons. Earlier in the day is often easier for monitoring.
- Day 2–3: repeat the same foodIf all looks good, you can slowly increase the amount.
- Keep other foods “known” during the windowIt’s okay to serve foods your baby has already tolerated—just avoid adding a new one.
- Track what you seeSkin, poop, spit-up/vomiting, mood, sleep—quick notes are enough.
(This is exactly the kind of flow Babywiz can help you log—food + day-by-day notes—so patterns are easier to spot.)
What symptoms should I watch for?
Some reactions happen quickly; others show up later. If you suspect a food allergy, the AAP advises reaching out to your child’s doctor with concerns.
Get urgent medical help if you notice trouble breathing, swelling of the face/lips, repeated vomiting, or your baby seems very unwell.
Can I introduce allergenic foods with the 3-Day Test?
Yes. Current CDC guidance says to introduce potentially allergenic foods when you introduce other foods—including egg and peanut—rather than delaying them.
If your baby has severe eczema or a known egg allergy, there are specific medical guidelines for peanut introduction (often involving pediatric guidance/testing and earlier supervised introduction).
Medical note: This article is for education and does not replace medical advice. If you’re worried about allergy risk, your pediatrician is the best partner.