The first year of a child’s life is often the year that parents become involuntary experts in infant illness. Colds, ear infections, stomach bugs, rashes, respiratory infections — the immune system is learning, and it learns partly by encounter. Most of what comes through is uncomfortable and manageable; a small fraction is serious and needs prompt medical attention. Knowing which is which, in the moment, is what this guide is about.

The organizing principle here is practical: for each common illness category, what does it look like, what is the typical course, what can be managed at home, and what are the signs that require a call to the pediatrician or a trip to the ER. For the triage decision itself, our urgent care vs. ER guide provides the full framework.

Respiratory illnesses: RSV, colds, and bronchiolitis

RSV (Respiratory Syncytial Virus) is the leading cause of hospitalization in infants under 12 months in the United States. Most adults and older children experience RSV as a cold. In infants — especially those under 6 months, premature infants, and infants with underlying heart or lung conditions — RSV can cause bronchiolitis, an infection of the small airways that leads to significant breathing difficulty.

Signs that distinguish RSV from a typical cold:

  • Wheezing — a high-pitched whistling sound on exhale
  • Visible retractions — skin pulling inward above the collarbone, between the ribs, or below the sternum with each breath
  • Rapid breathing (more than 60 breaths per minute in an infant at rest)
  • Nasal flaring
  • Poor feeding because the infant is working too hard to breathe and eat simultaneously
  • A color change — pale, dusky, or bluish tinge around the mouth or fingernails

Mild RSV with no breathing difficulty can be managed at home with saline nasal drops, a bulb syringe, and close monitoring. An infant who is breathing hard, not eating, or showing any of the signs above needs the ER. The CDC’s RSV information page provides current guidance on RSV prevention, including the nirsevimab (Beyfortus) antibody injection now recommended for infants through their first RSV season.

RSV immunization for infants: As of 2023, the CDC’s Advisory Committee on Immunization Practices recommends nirsevimab (not a vaccine — a monoclonal antibody) for most infants born during or entering their first RSV season (roughly October through March in most of the U.S.). Ask your pediatrician whether your infant qualifies and whether it is covered under your insurance.

The common cold in an infant runs 7–10 days. Congestion, runny nose, mild cough, and sometimes a low-grade fever are expected. The concern in very young infants is that obligate nose-breathing means significant congestion can make feeding difficult. Saline drops and suctioning before each feed help. Cold and cough medications are not recommended for infants under 2 years — they have not been shown to be effective and carry real risks.

Ear infections

Acute otitis media (middle ear infection) is one of the most common reasons for pediatrician visits in the first three years of life. Risk factors include attendance in group childcare, pacifier use after 6 months, and bottle feeding in a reclined position. Breastfeeding is protective.

Signs in an infant who cannot yet point at or describe an ear:

  • Fussiness and difficulty sleeping — ear pain typically worsens when lying flat
  • Ear-tugging (unreliable on its own — teething causes similar behavior)
  • Fever
  • Decreased response to sounds
  • Discharge from the ear canal (if the eardrum has perforated — paradoxically, perforation often provides some pain relief)

Ear infections are usually diagnosed by physical exam with an otoscope — a parent cannot reliably diagnose an ear infection based on symptoms alone. The current AAP guidelines recommend observation (waiting 48–72 hours before antibiotics) as an option for mild cases in children older than 6 months and 24 months with non-severe bilateral infections. For infants under 6 months, for severe infections, and for children with recurrent infections, antibiotics are generally recommended more promptly. This nuance is worth discussing with your pediatrician — the “just give antibiotics” approach has fallen out of favor because antibiotic resistance is a real concern, and the observation approach is safe for appropriate cases.

Gastroenteritis (stomach bugs)

Infant gastroenteritis — vomiting and diarrhea from a viral infection, most commonly rotavirus, norovirus, or adenovirus — is extremely common in the first two years of life. The primary risk is dehydration, not the infection itself.

Signs of dehydration in an infant:

  • Significantly fewer wet diapers than normal (less than 4 per day is concerning; none in 6+ hours is urgent)
  • No tears when crying
  • Dry mouth and lips
  • Sunken soft spot (fontanelle)
  • Unusual lethargy or limpness

Oral rehydration solution (Pedialyte or equivalent) — not water, not juice — is the correct rehydration for infants with gastroenteritis. Plain water does not replace the electrolytes lost with vomiting and diarrhea and can dilute sodium levels dangerously in infants. Juice makes diarrhea worse. The AAP’s recommendation is small, frequent amounts of oral rehydration solution — even a teaspoon every minute adds up.

Rotavirus vaccination (RotaTeq or Rotarix) is part of the standard immunization schedule and dramatically reduces the severity of rotavirus infection. If your infant is not yet vaccinated, ask about catch-up dosing at the next visit. The CDC’s rotavirus vaccination information covers the schedule and the evidence.

Return to normal feeding (breastmilk, formula, and appropriate solids for age) should begin as soon as the infant can tolerate it — there is no benefit to extended “BRAT” diets in infants, and early refeeding speeds recovery. Anti-diarrheal medications are not appropriate for infants.

Rashes

Infant skin is reactive, and rashes are extremely common in the first year. Most are not serious.

Newborn rashes that are normal: Erythema toxicum (blotchy red patches with white or yellow centers, appearing in the first 1–2 days), milia (tiny white bumps on the nose and chin from blocked pores), baby acne (pimple-like spots appearing around weeks 2–4), and cradle cap (seborrheic dermatitis on the scalp — yellow, flaky patches that look alarming but are benign).

Diaper rash is nearly universal. The standard treatment: keep the area dry, change diapers frequently, use a barrier cream (zinc oxide-based) at every change. A rash that has satellite lesions (small spots outside the main area), beefy red color, or has not improved in 2–3 days may be a yeast infection requiring an antifungal cream.

Eczema (atopic dermatitis) affects 10–20% of infants and typically appears as red, itchy, dry patches on the cheeks and extensor surfaces (outside of elbows and knees). Management is moisturizing — fragrance-free cream applied immediately after bathing to damp skin — and avoiding known triggers. Topical corticosteroids (mild ones like hydrocortisone 1%) are safe for short-term use on flares when recommended by the pediatrician. Eczema that is severe, infected (oozing, crusting), or not responding to basic management warrants a dermatologist or allergist referral.

Rashes that require prompt evaluation:

  • Any rash with high fever in an infant under 3 months
  • A rash that does not blanch (turn white) when pressed with a finger — this may indicate petechiae or purpura, which can signal a serious infection
  • A rash with difficulty breathing — possible allergic reaction
  • A widespread, rapidly spreading rash in a sick-appearing child

Fever: a brief summary

Full fever guidance is covered in our infant first aid essentials article, but the core thresholds:

  • Any fever in an infant under 3 months → ER immediately
  • Fever above 104°F (40°C) at any age → call pediatrician immediately
  • Fever 100.4–104°F in a 3–6 month infant → call pediatrician same day

Fever is a symptom, not a disease. The goal of evaluation is to find the cause. In infants under 3 months, the source of fever is often not obvious on physical exam, and evaluation typically includes bloodwork and sometimes a spinal tap to rule out bacterial meningitis — this is why all fevers in young infants are treated as potentially serious.

Jaundice

Jaundice — the yellow tint to skin and eyes caused by elevated bilirubin — appears in about 60% of term newborns and 80% of premature newborns in the first week of life. Mild jaundice in an otherwise healthy term newborn is physiologic and resolves without treatment. Severe jaundice, rapidly rising bilirubin, or jaundice that appears in the first 24 hours of life can cause brain damage (kernicterus) if untreated.

Bilirubin is typically checked before hospital discharge and again at the first pediatrician visit. If the level is in a range requiring treatment, phototherapy (bili lights) is the standard intervention. Parents should be alert to a baby who is very yellow, difficult to wake, or not feeding well — these are signs that jaundice may be severe and require same-day evaluation.

Frequently Asked Questions

My baby has had a cold for 10 days. Should I take them in? A cold that lasts 10–14 days in an infant is within normal range for a viral upper respiratory infection. Signs that warrant evaluation: fever returning after several days without it (may indicate a secondary bacterial infection like an ear infection), worsening rather than improving symptoms after day 7, significant difficulty breathing, or ear pain signs. A cold that simply drags on without those warning signs can generally be monitored at home.

How do I know if my baby has an ear infection? Ear infections cannot be reliably diagnosed at home — they require an otoscope exam. Fussiness, disturbed sleep, and ear-tugging in a child who recently had a cold are suggestive, but teething causes similar behavior. When in doubt, have the pediatrician look. Same-day sick visits are appropriate for suspected ear infections in infants.

Is it safe to use a saline nasal spray on my newborn? Yes. Saline nasal drops or spray (no medication — just saline) are safe from birth and are one of the most useful tools for congestion that interferes with feeding. A few drops followed by bulb syringe suction before feeds can significantly improve feeding efficiency in a congested infant.

My baby has eczema. Should I do an allergy test? Most infantile eczema is not driven by food allergies, and food allergy testing in infants with eczema is frequently misleading (many false positives). The AAP recommends managing eczema with moisturizing and topical treatments first, and reserving allergy testing for severe eczema that does not respond to treatment or for infants with other signs of food allergy. Discuss with your pediatrician before pursuing allergy testing.

When does jaundice become an emergency? Any jaundice in the first 24 hours of life is treated as potentially serious and requires same-day evaluation. After that, warning signs include jaundice that is spreading to the legs and soles of the feet, a very yellow or orange color, and an infant who is very sleepy, not feeding, or has a high-pitched cry. These signs warrant same-day or urgent evaluation.

Further Reading from Authoritative Sources