When should I worry about my baby vomiting?

Seek medical attention if your baby vomits more than 3 times in a few hours, if the vomit is green (bilious) or contains blood, if there are signs of dehydration (dry mouth, fewer wet diapers, tearless crying), if the baby is lethargic or inconsolable, or if the baby is under 3 months old. Isolated spit-ups after feeds are usually normal (physiological reflux).

How do I know if my baby is dehydrated?

Signs of mild dehydration include dry mouth and cracked lips, fewer wet diapers (less than 4 in 24 hours), and darker urine. In moderate dehydration, the eyes appear sunken, the baby cries without tears, and the fontanelle (soft spot) may be depressed. In severe dehydration, the baby becomes lethargic, the skin loses elasticity (skin pinch test), and there may be rapid heart rate. Moderate to severe dehydration is a medical emergency.

Can I give my baby homemade oral rehydration solution?

The WHO and the Brazilian Society of Pediatrics (SBP) do NOT recommend homemade oral rehydration solutions for babies. The risk of incorrect proportions is high and can cause dangerous electrolyte imbalances. Always use commercially prepared Oral Rehydration Solution (ORS), available at any pharmacy in Brazil without a prescription (ask for 'soro de reidratacao oral' or brands like Pedialyte). For breastfed babies, continue frequent breastfeeding — breast milk is the best rehydration fluid.

Is loose stool normal in breastfed babies?

Yes, it is normal for exclusively breastfed babies to have loose, yellowish, and frequent stools — they may have a bowel movement after every feed. This is NOT diarrhea. True diarrhea is characterized by a significant increase in frequency and volume of stools, with very watery consistency, sometimes with mucus or blood, and usually accompanied by other symptoms such as fever or vomiting.

When do I need to go to the emergency room?

Go to the ER immediately if: the baby is under 3 months with persistent vomiting or diarrhea; there is blood in the stool or vomit; the baby has not urinated for more than 6-8 hours; shows signs of moderate or severe dehydration (sunken eyes, lethargy, skin tenting); has a high fever (above 39°C/102.2°F); vomits everything ingested for more than 8 hours; or the abdomen is very distended and painful. In Sao Paulo, Hospital Sabara and Hospital Albert Einstein have excellent pediatric ERs.

Baby Vomiting and Diarrhea: Dehydration Signs and What to Do

If your baby is vomiting AND has diarrhea: start hydrating NOW. If your baby is unconscious or extremely lethargic, call SAMU 192 (Brazil's emergency number) immediately.

Acute gastroenteritis (vomiting + diarrhea) is one of the most common reasons for pediatric emergency visits, especially between April and July in Sao Paulo. The biggest danger is dehydration, which can become severe in babies very quickly. In this guide, I explain how to recognize dehydration signs, how to rehydrate correctly, when to go to the ER, and how to prevent it. If you are an expat family in Sao Paulo, check our guide to pediatric care in Brazil for helpful context on the healthcare system and where to find an English-speaking pediatrician.

How to Hydrate Your Baby Correctly

Oral rehydration is the most important treatment for gastroenteritis. The WHO, the Brazilian Society of Pediatrics (SBP), and ESPGHAN (European Society for Paediatric Gastroenterology) all recommend starting rehydration as early as possible.

Oral Rehydration Solution (ORS):available at any pharmacy in Brazil without a prescription. Ask for “soro de reidratacao oral” or brand names like Pedialyte. Offer in small sips by spoon or syringe (5-10 ml every 5-10 minutes)

Continue breastfeeding: breast milk is the best rehydration fluid for babies. Nurse more frequently and on demand

Formula: for babies on formula, continue the usual formula — do NOT dilute more than directed

Small, frequent amounts: offer little and often. Giving too much at once may trigger more vomiting

Monitor wet diapers: aim for at least 4-6 wet diapers per day as a sign of adequate hydration

Do NOT Use Homemade Rehydration Solutions!

The WHO and SBP do NOT recommend homemade oral rehydration solutions (water with salt and sugar) for babies. The risk of incorrect proportions is very high and can cause:

• Too much salt: hypernatremia, seizures, brain injury
• Too much sugar: worsened diarrhea (osmotic diarrhea)
• Missing electrolytes: commercial ORS contains potassium, citrate, and other electrolytes in the correct proportions

Always use pharmacy-bought ORS. In Brazil, Pedialyte and generic “soro de reidratacao oral” are affordable and widely available.

Is your baby vomiting or having diarrhea?

Schedule a consultation for evaluation and personalized hydration guidance. Bilingual care in Itaim Bibi, Sao Paulo.

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Dehydration Assessment Table: Mild vs. Moderate vs. Severe

Sign	Mild (<5%)	Moderate (5-10%)	Severe (>10%)
General status	Alert, irritable	Drowsy, listless	Lethargic, unconscious
Eyes	Normal	Sunken	Very sunken
Tears	Present	Reduced	Absent
Mouth/tongue	Dry	Very dry	Parched, cracked
Fontanelle (soft spot)	Normal	Depressed	Very depressed
Skin elasticity	Normal	Decreased	Skin tenting +
Urine	Reduced, dark	Very little	None (>6-8h)
Action	ORS at home + monitor	Urgent medical attention	ER NOW / SAMU 192

Source: WHO — Dehydration Management Plan. Adapted by the Brazilian Society of Pediatrics (SBP).

Common Causes of Vomiting and Diarrhea in Babies

Most cases of acute gastroenteritis in babies are caused by viruses. Understanding the cause helps you know what to expect. If your baby also has a fever, check our specific guide.

Viral Causes (most common)

• Rotavirus: leading cause in children under 5. Intense vomiting + watery diarrhea + fever. The rotavirus vaccine has reduced severe cases by 80%
• Norovirus: highly contagious, intense vomiting, lasts 1-3 days
• Adenovirus: can cause prolonged diarrhea (up to 14 days)

Other Causes

• Food poisoning: rapid onset (2-6 hours after ingestion)
• Bacterial infection: Salmonella, E. coli — blood/mucus in stool
• Food allergy/intolerance: can cause chronic vomiting and diarrhea
• Urinary tract infection: vomiting may be the only symptom in young babies

Feeding During Gastroenteritis

One of the biggest questions parents have is: “what can my baby eat?” Current guidelines from the SBP and ESPGHAN have changed significantly in recent years:

Continue Normal Diet (SBP and ESPGHAN)

Breastfeeding: continue on demand — it is the best treatment. Breast milk contains antibodies and factors that help intestinal recovery
Formula: continue the usual formula at correct dilution. Do NOT switch to lactose-free formula without pediatric guidance
Solid foods: for babies already on solid foods, offer the regular diet as soon as the baby accepts it. There is no need to restrict foods

Myth: The BRAT Diet

Prolonged dietary restriction (BRAT diet — bananas, rice, applesauce, toast) is NOT recommended by the SBP or ESPGHAN. This diet is low in nutrients and can delay recovery. Your baby needs calories and nutrients to heal. The priority is maintaining hydration with ORS and resuming normal feeding as soon as possible.

Medications: What Is Safe and What Is NOT

Do NOT use without a doctor's prescription

• Anti-emetics (for vomiting): ondansetron and others should ONLY be prescribed by a pediatrician after evaluation
• Anti-diarrheals (loperamide/Imodium): CONTRAINDICATED in children — can cause paralytic ileus and retain toxins in the gut
• Antibiotics: most gastroenteritis is viral — antibiotics do not help and may worsen symptoms

May be used (with guidance)

• Probiotics: Saccharomyces boulardii has evidence of reducing diarrhea duration by 1 day (ESPGHAN 2023). Consult your pediatrician for dosing
• Zinc: recommended by the WHO for children, can reduce duration and severity of diarrhea
• Fever medication: paracetamol (acetaminophen) or dipirona (metamizole, widely used in Brazil) if there is fever and discomfort. In Brazil, dipirona is a safe and common antipyretic that may be unfamiliar to expat families — your pediatrician can explain the options

When to Go to the Emergency Room

Go to the ER Immediately If:

Baby under 3 months with any persistent vomiting or diarrhea
Blood in stool or in vomit
Green (bilious) vomit — may indicate bowel obstruction
No urine for more than 6-8 hours
Moderate or severe dehydration signs (sunken eyes, lethargy, skin tenting)
High fever (>39°C / 102.2°F) combined with vomiting and diarrhea
Vomits everything ingested for more than 8 hours
More than 8 diarrhea episodes in 24 hours
Very distended and painful abdomen

Pediatric ERs in Sao Paulo (for Expat Families)

• Hospital Sabara: dedicated pediatric hospital with English-speaking staff. Av. Angélica, 1987 — Higienópolis
• Hospital Albert Einstein: world-class ER with multilingual staff. Av. Albert Einstein, 627 — Morumbi
• Hospital Sírio-Libanês: excellent pediatric ER. R. Dona Adma Jafet, 91 — Bela Vista
• SAMU 192:Brazil's emergency medical service (ambulance). Works like 911/999

Need medical guidance now?

Dr. Paula offers bilingual pediatric care in Itaim Bibi, Sao Paulo. Appointments available within 24-48 hours.

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Prevention: How to Protect Your Baby

Gastroenteritis cannot always be prevented, but these measures significantly reduce the risk:

Rotavirus vaccine

Available in the Brazilian vaccination schedule (free at public health centers and private clinics). Given at 2 and 4 months of age. Has reduced rotavirus hospitalizations by 80% in Brazil.

Hand washing — the most effective measure

Wash hands with soap and water for at least 20 seconds before preparing food, after diaper changes, and after using the bathroom. Note: hand sanitizer (alcohol gel) is NOT effective against norovirus and rotavirus.

Exclusive breastfeeding until 6 months

Breast milk contains antibodies (IgA) that protect the baby's gut against infections. Exclusively breastfed babies have lower risk and milder gastroenteritis episodes.

Filtered or boiled water

In Brazil, always use filtered or boiled water for preparing baby food and formula. Wash fruits and vegetables before consumption. Tap water quality varies by neighborhood — when in doubt, use filtered water.

Food safety during solid food introduction

Thoroughly clean all baby utensils. Do not offer food that has been out of the refrigerator for more than 2 hours. Extra caution is needed during warmer months (October-March in Brazil).

Isolation during illness

Viral gastroenteritis is highly contagious. Keep a sick child at home, away from other children, for at least 48 hours after the last episode of vomiting or diarrhea. Notify your child's daycare or school.

When to See the Pediatrician (Non-Emergency)

Not every case of vomiting and diarrhea is an emergency. But you should schedule a pediatric visit if:

Diarrhea persists for more than 5-7 days, even without dehydration signs

The baby is not gaining weight adequately after recovery

There are recurrent episodes of vomiting and diarrhea (may indicate food allergy or pathological reflux)

The baby has a fever lasting more than 3 days

You have questions about hydration or feeding during the illness

Scientific References

• Brazilian Society of Pediatrics (SBP). Practical Update Guide: Acute Diarrhea in Childhood. Gastroenterology Department, 2024.
• World Health Organization (WHO). The Treatment of Diarrhoea: A Manual for Physicians and Other Senior Health Workers. 4th rev., 2005.
• ESPGHAN (Guarino A, et al.). European Society for Paediatric Gastroenterology, Hepatology, and Nutrition/European Society for Paediatric Infectious Diseases Evidence-Based Guidelines for the Management of Acute Gastroenteritis in Children in Europe: Update 2023. JPGN, 2023.
• Brazilian Ministry of Health. National Vaccination Calendar — Human Rotavirus Vaccine. PNI, 2025.