The most important thing to give a 9-month-old with diarrhea is fluids, especially breast milk, formula, or an oral rehydration solution. Dehydration is the real danger with infant diarrhea, not the diarrhea itself. Most cases resolve on their own within a few days, but keeping your baby hydrated and fed throughout is what matters most.
Breast Milk and Formula Come First
If you’re breastfeeding, keep breastfeeding. Breast milk is easy to digest, provides antibodies, and naturally replaces lost fluids. Offer the breast more frequently than usual, even if your baby’s stools are still loose. There’s no reason to pause or reduce breastfeeding during a bout of diarrhea.
If your baby is on formula, continue making it at full strength. A common misconception is that you should water down formula during illness, but diluting it reduces the calories and nutrients your baby needs to recover. Stick with your normal preparation and offer bottles more often.
When to Add Oral Rehydration Solution
Oral rehydration solutions (sold as Pedialyte, Hydralyte, and store-brand equivalents) are specially formulated to replace the water, sodium, potassium, and sugar your baby loses with each watery stool. They come in ready-to-drink bottles, ice pops, powder sachets, and dissolving tablets. If you use a powder or concentrate, follow the package directions exactly. Getting the ratio wrong can make things worse.
A good general target is at least 5 mL of fluid per kilogram of your baby’s body weight every hour. For a typical 9-month-old weighing around 8 to 9 kg, that works out to roughly 40 to 45 mL (about 1.5 ounces) per hour. Offer small sips frequently rather than large amounts at once, especially if your baby is also vomiting. You can use a syringe, spoon, or small cup if your baby won’t take a bottle.
If you don’t have a rehydration solution on hand, you can offer small amounts of cooled, boiled water alongside breast milk or formula. Watered-down apple juice is a temporary backup, but full-strength fruit juice should be avoided entirely. The sugar in undiluted juice pulls extra water into the intestines and can make diarrhea worse.
What Solid Foods to Offer
At 9 months, your baby is likely eating some solid foods already. There’s no need to stop. In fact, continuing to eat helps the gut recover faster. Offer whatever your baby normally tolerates well, focusing on simple, bland options. Good choices include mashed banana, plain rice cereal (in moderation, not as the sole grain), cooked and mashed sweet potato, plain yogurt, and pureed chicken or turkey. These provide calories, iron, and zinc that your baby needs during illness.
You may have heard of the BRAT diet (bananas, rice, applesauce, toast). While these foods are gentle on the stomach, pediatric guidelines no longer recommend restricting your baby to only those items. A BRAT-only diet is too low in protein, fat, and key nutrients for a growing infant. Think of those foods as part of the mix, not the entire menu.
Avoid anything new during the illness. If your baby reacts to an unfamiliar food with more diarrhea, a rash, or vomiting, you won’t be able to tell whether it’s the illness or a food sensitivity. Stick with foods your baby has already eaten without problems.
Drinks and Foods to Avoid
Full-strength fruit juice, soda, and sports drinks are all off the table. They contain too much sugar and not enough electrolytes, which worsens diarrhea by drawing fluid into the gut. Cow’s milk (as a drink, not in cooked foods) is also best avoided during active diarrhea in babies under 12 months, as it’s harder to digest when the intestinal lining is irritated. Plain water in small amounts is fine alongside breast milk or formula, but water alone doesn’t replace the electrolytes your baby is losing.
Do Not Give Over-the-Counter Anti-Diarrheal Medication
Loperamide (the active ingredient in Imodium) is not recommended for children younger than 2 years. The FDA has documented serious side effects in young children who received it, including dangerous heart rhythm problems. Bismuth subsalicylate (Pepto-Bismol) is also unsafe for infants. No over-the-counter anti-diarrheal medication is appropriate for a 9-month-old. The diarrhea itself is your baby’s body clearing out an infection or irritant, and stopping it artificially in a young infant carries real risks.
Probiotics and Zinc
Two specific probiotics have strong evidence behind them for pediatric diarrhea: Lactobacillus rhamnosus GG (often labeled LGG) and Saccharomyces boulardii. The European Society for Pediatric Gastroenterology recommends both for preventing and shortening antibiotic-associated diarrhea in children. In clinical trials, children who received LGG alongside antibiotics had roughly half the rate of diarrhea compared to children who didn’t. These probiotics are available in infant-specific drops and powders. If your baby’s diarrhea is linked to an antibiotic course, asking your pediatrician about adding one of these is reasonable.
The World Health Organization recommends 20 mg of zinc per day for 10 to 14 days for children over 6 months with diarrhea. Zinc helps the intestinal lining repair itself and can shorten the duration of illness. This recommendation is especially emphasized in low- and middle-income countries where zinc deficiency is common, but it applies broadly. Zinc supplements formulated for infants are available as dissolvable tablets or syrups.
How to Spot Dehydration
Dehydration can develop quickly in a small baby. The signs to watch for include fewer wet diapers than usual (fewer than 4 to 6 in 24 hours is a red flag), no tears when crying, a dry mouth, unusual sleepiness or irritability, and a sunken soft spot (fontanelle) on top of your baby’s head. That last sign, where the fontanelle dips inward visibly, indicates moderate to severe dehydration and needs medical attention promptly.
Other reasons to seek care quickly: blood or mucus in the stool, a fever above 102°F (38.9°C) that won’t come down, vomiting so persistent that your baby can’t keep any fluids down for several hours, or diarrhea that lasts more than a few days without improvement. A baby who seems limp, unresponsive, or refuses to drink anything needs to be seen right away.
Protecting Your Baby’s Skin
Frequent watery stools are rough on a baby’s skin. Diaper rash during diarrhea is extremely common and can develop within hours. Change diapers as soon as possible after each stool. Use warm water and a soft cloth to clean the area gently, and pat dry rather than rubbing. Skip baby wipes with fragrance or alcohol, which can sting irritated skin.
Apply a thick layer of barrier cream or ointment with every diaper change. Products containing zinc oxide or petroleum jelly work best. You don’t need to scrub off the previous layer of cream at each change. If it’s still clean, just add more on top. Letting your baby go diaper-free on a towel for short stretches gives the skin a chance to air dry, which speeds healing.