The first cold in a baby is rough — for them and for you. They can't blow their nose. Feeding gets harder because they breathe through their nose. They cry differently. They have a temperature for the first time and you're trying to remember whether 38.2°C is the number you should panic about. Most of this passes in a week and turns out to be a viral cold that does what colds do.
This article tells you what a normal cold looks like in a baby, what helps, what to leave alone, and the specific thresholds for picking up the phone or driving to A&E. By school age, most children have had 50+ respiratory infections — they're how the immune system learns. But babies under 3 months are a special case, and a few signs in any baby need fast attention.
Logging temperatures, symptoms, and how each illness moves through your baby in Healthbooq gives you a record that's genuinely useful at GP appointments and helps you recognise your baby's pattern.
What a Normal Cold Looks Like
A typical cold in a baby runs like this:
- Days 1–2: clear runny nose, mild low-grade temperature (often under 38.5°C), fussiness, sneezing.
- Days 2–4: nasal discharge thickens, often turning yellow or green. This is the immune system working — it doesn't mean bacterial infection and doesn't need antibiotics.
- Days 3–5: congestion is usually at its worst. Feeding is hardest here.
- Days 5–10: symptoms gradually settle. A residual cough can linger 2 to 3 weeks.
Babies under about 3 months are obligate nose breathers — they don't reliably switch to mouth breathing. That's why a blocked nose causes more trouble for a baby than for you and why feeds get short and frustrating during the worst of the congestion.
What Helps
Saline nasal drops. Plain isotonic saline (available without prescription, around £3–5) put into each nostril 5 to 10 minutes before a feed. They thin the mucus so the baby can actually breathe and feed. This is the single most useful thing you can do.
A nasal aspirator. A bulb syringe or a NoseFrida (the suction-tube one) clears the loosened mucus. Aspirate after the saline has had time to work. Don't be too aggressive — the lining is delicate.
Upright positioning. When the baby is awake, holding them more upright helps drain. Sleep must stay flat on the back on a firm surface — no pillows, no wedges, no bouncers, no inclined sleepers (these have been linked to infant deaths). If you want to prop the head end of the cot, put a firm rolled towel under the mattress, not under the baby.
Paracetamol or ibuprofen for discomfort, not for the number. Paracetamol from 2 months (and over 4kg). Ibuprofen from 3 months (and over 5kg). Use the dose on the bottle for your baby's weight. The point is comfort. A baby with 38.5°C who's feeding and reasonably content doesn't need medicine; a baby with 38.2°C who's miserable does.
Fluids. Breastfeed more often if you're nursing — small frequent feeds are better than fighting for big ones. For formula-fed babies offer feeds more often, smaller amounts. Over 6 months, plain water is fine alongside milk.
Steam from a bath. Sitting in a steamy bathroom for 10 minutes before bed can ease congestion. Don't use a vapouriser with menthol products near a baby under 2.
What Not to Use
Over-the-counter cold and cough medicines. Decongestants, antihistamines, cough suppressants — none are recommended under 6 years. The MHRA in the UK and FDA in the US have both restricted them in young children because they don't work and they have real side effects (drowsiness, agitation, very rarely serious cardiac events).
Menthol rubs (Vicks and similar). Don't use on or near the face of a baby under 2. They've been linked to mucus over-production and respiratory distress.
Antibiotics. Colds are viral. Yellow or green snot is not bacterial infection — it's immune cells doing their job. Antibiotics will not shorten a cold and will increase the risk of antibiotic-resistant infections later.
Honey for cough. Useful from 1 year onwards for an irritating cough. Never under 1 — risk of infant botulism.
Cold or Flu? Cold or Something Worse?
Influenza in babies looks like a cold but with higher fever (often 39°C+), more obvious lethargy, and faster onset. RSV (respiratory syncytial virus) starts as a cold but in babies under 1 — especially under 3 months and ex-prems — can progress to bronchiolitis with fast or laboured breathing, wheezing, and feeding trouble around days 3 to 5. RSV peaks in autumn and winter.
When to Get Medical Help
Call 999 or go to A&E now if:
- Severe difficulty breathing — grunting with each breath, ribs sucking in clearly, head bobbing with breathing, blue lips or tongue, pauses in breathing
- A floppy, very drowsy, or unresponsive baby
- A high-pitched, unusual cry you can't soothe
- A non-blanching rash (doesn't fade when you press a glass against it)
- A seizure
Phone 111 or your GP today if your baby is under 3 months and:
- Has any temperature of 38°C or above (this rule is firm — fever in a small baby always needs same-day assessment)
- Is feeding much less than half their usual amount
- Has had fewer than 4 wet nappies in 24 hours
Phone 111 or your GP today if your baby is 3 months or older and:
- Has a temperature over 39°C lasting more than 3 days
- Has a fever that came back after settling for 24+ hours (often points to a secondary bacterial infection like an ear infection or pneumonia)
- Is breathing faster than usual at rest (over 60 breaths/min in babies under 1, over 40 in 1–2 year olds)
- Is pulling at the ear, crying inconsolably especially when laid flat
- Is consistently unable to feed because of congestion
- Is dry-nappied for more than 8 hours, has no tears when crying, or has a sunken fontanelle (signs of dehydration)
- Has been getting worse rather than better from day 5 onwards
- Doesn't look right to you. Trust this — parents are very good at spotting "off" before doctors are.
Key Takeaways
Babies get 6 to 10 colds a year in the first two to three years — that's normal, not a sign of weak immunity. Most colds are caused by rhinovirus and clear in 7 to 10 days without treatment. The mainstays of care are saline nasal drops before feeds, paracetamol or ibuprofen for discomfort (not as a fever target), and keeping fluids up. Over-the-counter cold and cough medicines are not recommended under age 6. The signs that turn an ordinary cold into a GP or A&E visit are clear: any fever in a baby under 3 months, breathing that's working too hard, dehydration, fever returning after it had settled, or a baby who's getting worse instead of better past day 5.
