Nasal congestion for babies and little kiddos can be extremely long lasting after initial colds for a few reasons.
1. Their nasal passages are just much smaller so any little bit of snot or boogers has a bigger impact and is always much louder than in older kids and adults.
2. They don't have big enough sinuses to hold extra snot so everything just hangs out in the nose. Where it takes 2-4 weeks for a person to get rid of all the snot and viral particles after a cold we as adults and with older kids (over the age of 5-6 years old) have sinuses to hold this extra snot while the body gets rid of it during that time so we don't sound congested 7-10 days after initial illness. Kids without sinuses yet typically are congested after colds for 2-4 weeks due to this.
3. The younger you are the more new viruses your body is dealing with for the first time - meaning that during fall and winter especially kiddos get back to back to back to back..etc new viral colds and basically can be snotty the entirety of cough cold season.
So how do we know it is expected post viral cold congestion vs something else. There are some clues we look for at home and in clinic to help figure this out. We expect that the congestion is gravity dependent. Meaning that if the kiddo is in a position that prevents drainage of the snot then they will sound more congested and/or have more post nasal drip cough. We expect when littles are laying down there is less drainage so congestion worsens. We expect that post nasal drip and post nasal drip cough from congestion is worse when laying down, first thing in the morning, and when they move their head around to dislodge snot. It should improve the more upright and active they are due to the architecture of the nose and the path that snot likes to take due to gravity.
Other possible causes of prolonged congestion in kids can be seasonal/environmental allergens. As my allergist friends say - any one can develop an allergy at any time. The tricky thing is that with kids under one it is very tough to test for because skin testing is the gold standard for environmental allergy testing but kids skin under 2 years of age and more so under 1 year of age is so sensitive to anything new on it that the rate of false positives for allergy skin testing under the age of one is almost the same as true positives. So allergists won't test kiddos under the age of 1 for allergies unless they have demonstrated anaphylaxis to a probable trigger. So if we are still concerned for a cat dander allergy we can get Madeline tested after she turns 1.
What we don't expect for continue or prolonged nasal congestion as we are getting over a cold in those under 1 year of age are continued fevers longer than 3 days or return of fevers a few days after lack of fever for over 24 hours. That is usually ear infection til proven otherwise, especially if we have increase in more snot suddenly. For a kiddos first cold season or first day care/preschool season we basically expect a new illness (mostly upper respiratory colds) every 2-4 weeks and fevers once a month as the body gets used to all the new antigens and viral friends kiddos friends and family like to share during this time. Also we expect that congestion would improve after steamy showers, saline nasal drops/suction. It should not prevent majority of feeding to the point we are losing weight and should not result in sustained increase work of breathing even after decongestion measures are taken if that is happening time to call your friendly neighborhood pediatrician for a good exam in clinic.