A congested 5-month-old can’t simply switch to breathing through their mouth the way you or an older child would. Babies this age rely almost entirely on their noses to breathe, which means even mild stuffiness can interfere with feeding, sleeping, and comfort. The good news: most infant congestion is caused by a common cold and clears up within about two weeks, and you can do a lot at home to help your baby breathe easier in the meantime.
Why Congestion Hits Babies Harder
Until roughly 3 months of age, babies breathe almost exclusively through their noses (except when crying). By 5 months, your baby has started to develop some ability to mouth-breathe, but nasal passages are still tiny and easily blocked by even a small amount of mucus. When those passages clog, your baby can’t comfortably suck and breathe at the same time, which is why feeding often becomes the first obvious struggle.
Saline Drops and Suctioning
The most effective tool you have is a simple saline-and-suction routine. Lay your baby on their back, then place 3 to 4 saline drops into each nostril using a nose dropper. Hold your baby with their head tilted slightly back for about a minute so the saline has time to thin the mucus. Then suction with a bulb syringe or a similar nasal aspirator.
To use a bulb syringe: squeeze all the air out of the bulb first, gently place the tip into one nostril, then release the bulb so it draws mucus in. Squeeze the mucus onto a tissue and repeat on the other side. The key detail many parents miss is timing. Always do this before a feeding, not after. Suctioning on a full stomach can cause vomiting.
Limit suctioning to no more than 4 times a day. More than that can irritate the delicate lining inside your baby’s nose, which actually makes swelling and congestion worse. If your baby doesn’t seem congested at a particular feeding, skip it.
Using a Humidifier Safely
A cool-mist humidifier in your baby’s room adds moisture to the air, which helps keep nasal passages from drying out and mucus from thickening. But a dirty humidifier can spray mold and bacteria into the air, so how you maintain it matters as much as using it.
Fill it with distilled water only, not tap water. Minerals in tap water create a fine white dust and feed bacterial growth inside the tank. Once a week, fill the tank with enough distilled white vinegar to cover all surfaces that touch water, let it sit for 20 minutes, scrub the cracks with a toothbrush, rinse thoroughly, and air dry. Keep the bedroom door open when the humidifier is running so moisture doesn’t build up in an enclosed space.
Keeping Your Baby Fed and Hydrated
A stuffed nose is the most common reason a young baby suddenly refuses the breast or bottle. They literally can’t breathe while sucking. The fix is straightforward: clear the nose with saline and suction right before each feeding so the airways are as open as possible. You may need to offer shorter, more frequent feeds rather than waiting for a full session. If your baby is getting tired quickly and pulling away repeatedly, that’s normal during a cold, but watch for signs of dehydration like fewer wet diapers (fewer than 4 in 24 hours), no tears when crying, or a sunken soft spot on top of the head.
What Not to Do
Over-the-counter cough and cold medicines should never be given to infants. The American Academy of Pediatrics warns against all OTC cough and cold products for children under 4 years old because of the risk of dangerous side effects. There is no safe dose for a 5-month-old, regardless of what older packaging or advice from relatives might suggest.
You may also have heard about elevating the head of the crib to help with congestion. This is not safe. Federal sleep guidelines are clear that a baby’s sleep surface must be firm, flat, and level. Inclined surfaces cause a baby’s body to slide downward, which can push the chin toward the chest and obstruct breathing, a situation called positional asphyxia. Sleep positioners, rolled towels under the mattress, and wedges all fall into this category. Your baby should sleep on their back on a flat surface with nothing else in the crib.
Steam and Other Comfort Measures
A steamy bathroom can offer temporary relief. Run a hot shower with the bathroom door closed for a few minutes, then sit in the room (not in the shower) with your baby on your lap for 10 to 15 minutes. The warm, moist air loosens mucus and can make suctioning more productive afterward. Gentle upright holding during the day also helps mucus drain naturally. Skin-to-skin contact can soothe a fussy, congested baby and makes it easier to monitor their breathing.
How Long Congestion Typically Lasts
A standard infant cold runs about two weeks from start to finish. Fever, if present, usually resolves within 2 to 3 days. Nasal drainage is the longest-lasting symptom, persisting for 7 to 14 days. A cough can linger for 2 to 3 weeks even after the nose clears up. The worst congestion is usually in the first few days, and you’ll likely notice gradual improvement by the end of the first week.
Signs That Need Medical Attention
For a baby between 3 and 6 months old, a rectal temperature above 100.4°F (38°C) warrants a call to your pediatrician. So does a lower temperature if your baby seems unusually lethargic or unwell. Beyond fever, watch for these specific signs that suggest something more than a simple cold:
- Earache clues: pulling at an ear, new onset of intense crying, or fluid draining from an ear
- Fever lasting more than 3 days, or fever that goes away and then returns after being gone for over 24 hours
- Nasal discharge continuing beyond 14 days
- Labored breathing: ribs visibly pulling inward with each breath, flaring nostrils, or a whistling sound from the chest (not just noisy nose breathing)
- Refusing to eat even after thorough nasal clearing, or showing signs of dehydration
These can signal a secondary infection like an ear infection or pneumonia, both of which are treatable but need a doctor’s evaluation. A simple cold doesn’t require a visit, but complications that develop on top of one sometimes do.