Common Baby Illnesses: A Parent's Guide to Colds, RSV, and More

Here’s a number that might surprise you: the average baby catches eight to ten colds in their first two years of life. If your little one seems to have a permanent runny nose from October to March, you’re not imagining things — and you’re definitely not doing anything wrong.

Babies are encountering the world’s germs for the very first time, and their immune systems are learning on the job. Most childhood illnesses are mild and self-limiting, but knowing what you’re dealing with — and when something needs medical attention — can turn a stressful week into a manageable one.

The Common Cold

The humble cold is by far the most frequent illness your baby will face. It’s caused by over 200 different viruses (rhinoviruses being the usual suspects), which is why your baby can catch cold after cold without building lasting immunity.

What it looks like

Runny or stuffy nose (clear mucus that may turn yellow or green — color alone doesn’t mean it’s bacterial)
Sneezing and mild cough
Slightly reduced appetite
Low-grade fever (usually under 101°F / 38.3°C)
Fussiness, especially at night when congestion worsens

How long it lasts

Most colds peak around days 2 to 3 and gradually improve over 7 to 10 days. A lingering cough can stick around for up to two weeks, which is normal.

What you can do

Saline drops and a bulb syringe (or nasal aspirator) are your best friends. A couple of saline drops in each nostril followed by gentle suction can provide immediate relief, especially before feeds and sleep.
Run a cool-mist humidifier in the nursery. Moist air helps loosen congestion.
Offer extra fluids. Breast milk or formula for babies under 6 months; water and diluted juice for older babies.
Elevate the head of the crib slightly by placing a folded towel under the mattress (not under the baby). This helps with drainage.

What to avoid

No over-the-counter cold medicine for children under 2. The FDA advises against it — these products aren’t proven effective in young children and carry real risks.
No honey for babies under 12 months (risk of infant botulism).
No vapor rubs on the face or near the nostrils of babies — they can irritate airways.

RSV (Respiratory Syncytial Virus)

RSV is a respiratory virus that nearly every child catches by age 2. For most older babies and toddlers, it looks like a bad cold. But for young infants — especially those under 6 months, premature babies, or those with heart or lung conditions — RSV can progress to bronchiolitis or pneumonia and become serious.

What makes RSV different from a cold

RSV often starts like a cold but then moves deeper into the lungs. The hallmark is wheezing and labored breathing — you might notice your baby’s nostrils flaring, their ribs pulling in with each breath, or a rapid breathing rate.

Warning signs to watch for

Breathing faster than 60 breaths per minute
Visible rib retractions (skin pulling in between or below the ribs)
Flaring nostrils
Blue or gray color around the lips or fingernails
Pauses in breathing lasting more than 10 seconds
Refusing to feed or only taking small amounts
Significantly fewer wet diapers than usual

RSV prevention

The AAP recommends RSV immunization for all infants. As of 2025–2026, options include monoclonal antibody products like nirsevimab, which provides passive protection through the RSV season. Talk to your pediatrician about the best option for your baby, especially if they’re born during or just before RSV season (typically fall through early spring).

Treatment

There’s no antiviral medication for RSV. Treatment is supportive — keeping the airways clear, ensuring adequate hydration, and monitoring breathing. Some babies need hospitalization for supplemental oxygen or IV fluids. Most healthy babies recover fully within one to two weeks.

Ear Infections (Otitis Media)

Ear infections are the second most common reason parents bring babies to the pediatrician, right after colds — and for good reason. Babies’ Eustachian tubes are shorter and more horizontal than adults’, making it easier for fluid to get trapped and bacteria to grow.

Signs your baby might have an ear infection

Tugging or pulling at one or both ears
Increased fussiness, particularly when lying down
Difficulty sleeping
Fever (not always present)
Fluid draining from the ear
Reduced appetite or difficulty feeding
Not responding to quiet sounds as usual

Treatment approaches

The AAP recommends a “watchful waiting” approach for some ear infections in children over 6 months with mild symptoms. This means monitoring for 48 to 72 hours before starting antibiotics, since many ear infections — particularly those caused by viruses — resolve on their own.

However, antibiotics are typically prescribed right away for:

Babies under 6 months
Children with severe symptoms (fever over 102.2°F / 39°C, significant ear pain)
Children with infection in both ears
Children with ear drainage

Pain management with acetaminophen or ibuprofen (age-appropriate dosing) is important regardless of whether antibiotics are used.

Gastroenteritis (Stomach Bug)

Rotavirus, norovirus, and other gastrointestinal viruses cause vomiting, diarrhea, and general misery. The good news: since the introduction of the rotavirus vaccine, severe rotavirus gastroenteritis has dropped dramatically.

What to expect

Vomiting that usually peaks in the first 24 hours
Watery diarrhea that may last 5 to 7 days
Low-grade fever
Decreased appetite
Belly cramps and general fussiness

The biggest risk: dehydration

For babies, the primary danger of gastroenteritis isn’t the virus itself — it’s losing too much fluid. Watch for these signs of dehydration:

Fewer than 4 wet diapers in 24 hours (for infants)
No tears when crying
Sunken soft spot (fontanelle)
Dry mouth and lips
Listlessness or extreme sleepiness
Sunken eyes

How to manage it

Keep breastfeeding. Breast milk is well-tolerated even during stomach bugs and provides antibodies.
Offer small, frequent amounts of breast milk, formula, or an oral rehydration solution like Pedialyte.
Don’t give fruit juice, sports drinks, or plain water as the primary fluid replacement for babies — the sugar and electrolyte balance isn’t right.
The BRAT diet (bananas, rice, applesauce, toast) is no longer specifically recommended. Once your baby is ready for solids again, offer their normal diet.

Hand, Foot, and Mouth Disease (HFMD)

Caused primarily by coxsackievirus, HFMD is extremely common in babies and toddlers, especially during summer and early fall. It sweeps through daycares like wildfire, and the name tells you exactly where it shows up.

Symptoms

Fever lasting 2 to 3 days
Painful sores in the mouth (on the tongue, gums, and inside of cheeks)
Blister-like rash on the palms, soles of the feet, and sometimes the buttocks and legs
Reduced appetite (those mouth sores really hurt)
Drooling more than usual
General irritability

Managing the discomfort

Mouth sores can make eating and drinking painful, so hydration is the priority:

Offer cold foods like chilled purees or yogurt
Avoid acidic or salty foods that sting
Acetaminophen or ibuprofen for pain and fever
Cold drinks and ice pops for older babies

HFMD typically resolves within 7 to 10 days. The rash may look alarming, but it’s usually not itchy and heals without scarring. Note that HFMD is highly contagious — your baby is most infectious during the first week but can shed the virus in stool for weeks afterward.

Croup

That distinctive barking cough at 2 a.m. — the one that sounds like a seal — is usually croup. It’s caused by a viral infection (most commonly parainfluenza) that inflames the upper airway, producing that characteristic sound along with a hoarse voice and sometimes stridor (a high-pitched noise when breathing in).

Croup tends to be worse at night

This is because lying down increases congestion in the upper airway. Many parents discover croup in the middle of the night when their baby wakes with that startling barking sound.

Home treatment

Cool night air can work wonders. Bundle your baby up and step outside for 10 to 15 minutes. The cool, moist air helps reduce airway swelling.
Run a hot shower and sit in the steamy bathroom for 15 to 20 minutes.
Cool-mist humidifier in the bedroom.
Keep your baby calm. Crying and agitation worsen the airway narrowing.

When croup needs medical attention

Stridor at rest (not just during coughing or crying)
Difficulty swallowing or excessive drooling
Blue or gray skin
Severe retractions (skin pulling in sharply with each breath)
Your baby seems to be struggling to breathe

Your pediatrician may prescribe a single dose of oral dexamethasone, which is very effective at reducing airway inflammation.

Conjunctivitis (Pink Eye)

Pink eye in babies can be caused by viruses, bacteria, or a blocked tear duct. Newborns may also develop chemical conjunctivitis from the antibiotic eye drops given at birth, which resolves on its own.

Bacterial vs. viral

Bacterial: Thick yellow or green discharge, eyelids crusted shut in the morning, may affect one or both eyes. Often needs antibiotic eye drops.
Viral: Watery discharge, often accompanies a cold, usually affects both eyes. Resolves on its own.

When to see the doctor

Always have a doctor evaluate pink eye in babies under 1 month old. For older babies, see your pediatrician if there’s significant swelling, the baby seems to be in pain, symptoms worsen after 2 to 3 days, or vision seems affected.

Building a Sick-Baby Toolkit

Keep these supplies on hand so you’re not making a pharmacy run at midnight:

Digital rectal thermometer
Saline nasal drops and a nasal aspirator
Infant acetaminophen (for babies 2+ months)
Infant ibuprofen (for babies 6+ months)
Oral rehydration solution (Pedialyte or equivalent)
Cool-mist humidifier
Bulb syringe (a backup for the nasal aspirator)
Petroleum jelly

Frequently Asked Questions

Why does my baby seem to be sick all the time?

If your baby is in daycare or has older siblings, frequent illnesses are completely normal. Babies catch an average of 8 to 10 viral infections per year in their first 2 years. Each illness is actually training the immune system. It doesn’t feel like it when you’re up at 3 a.m. with a congested baby, but this is healthy development happening in real time.

Can I send my baby to daycare with a runny nose?

Policies vary, but most daycares allow children with clear or slightly colored nasal discharge as long as there’s no fever and the child is well enough to participate. A perpetual runny nose during cold season is practically a daycare membership card.

How do I know if my baby’s cold has turned into something more serious?

Watch for signs that the illness is progressing rather than improving: fever developing after several days of cold symptoms (suggesting a secondary bacterial infection), breathing difficulties, persistent ear pain, symptoms lasting more than 10 to 14 days without improvement, or your baby becoming less responsive or refusing to feed.

Should I keep my baby away from other children to prevent illness?

Some exposure to germs is actually beneficial for immune system development. Obviously, keep your baby away from people who are actively sick with fevers or vomiting, and practice good hand hygiene. But living in a bubble isn’t realistic or necessarily helpful in the long run.

When should I be worried about dehydration?

The key indicators are urine output and behavior. Fewer than 4 wet diapers in 24 hours, no tears when crying, a sunken soft spot, dry mucous membranes, or unusual lethargy all warrant a call to your pediatrician. Dehydration can progress quickly in small babies, so don’t wait to seek help if you’re concerned.

Sources

American Academy of Pediatrics. “The Common Cold.” HealthyChildren.org, updated 2024.
Ralston, S.L., et al. “Clinical Practice Guideline: The Diagnosis, Management, and Prevention of Bronchiolitis.” Pediatrics, vol. 134, no. 5, 2014, pp. e1474–e1502.
American Academy of Pediatrics. “Recommendations for the Prevention of RSV Disease in Infants and Children.” Pediatrics, vol. 156, no. 5, 2025.
Lieberthal, A.S., et al. “The Diagnosis and Management of Acute Otitis Media.” Pediatrics, vol. 131, no. 3, 2013, pp. e964–e999.
Centers for Disease Control and Prevention. “Rotavirus Vaccination.” CDC.gov, updated 2024.
World Health Organization. “Integrated Management of Childhood Illness (IMCI).” WHO, 2014.
U.S. Food and Drug Administration. “Should You Give Kids Medicine for Coughs and Colds?” FDA.gov, updated 2023.