There are many reasons why babies have a yellow nose, in fact most parents will have experienced that babies start with a clear nose with a little yellow nose behind it and then they get better, but of course some of them become endlessly runny, or clear and yellow noses alternately last. First of all, most babies with yellow nose start from clear snot, and clear snot can be caused by cold or allergic rhinitis. If it is caused by a cold, there is often a little yellow snot during the recovery period, which is very short and most children can recover quickly on their own. However, if a child has clear runny nose caused by allergic rhinitis, the process of runny nose itself will last longer due to allergy, and then the yellow runny nose will often be repeated and difficult to heal by itself. In addition, some children have weak resistance, and the runny yellow nose becomes sinusitis after the runny nose, resulting in recurrent nasal-sinusitis. Therefore, when a baby has a yellow runny nose, if the yellow runny nose is very little and it heals itself quickly, it should be a process of healing from a cold, but if it continues to appear, it should be combined with bacterial infection or combined with rhinosinusitis, so we should pay more attention to it.