Written By: Alan Greene, M.D.
When a child wakes up with a runny nose and feeling yucky, parents are faced with a big decision. Should I send my child to school or daycare? Is this something that’s contagious? Will my child be sicker if they go out? Or is this an allergy that needs relief, but won’t be made better by keeping the child home.
Telling the difference between a cold and an allergy can be really, really tricky because they're in some ways the same thing. In both cases the immune system identifies something that doesn't belong and uses nasal discharge to get rid of it.
In the case of a cold, it’s a virus. In the case of nasal allergies it might be pollen. Or it might be an allergy to dust mites – something that can cause allergies all year round but is rampant in the winter months. The body has a similar repertoire of stuff to try to get rid of the invader no matter the cause. It creates sneezing to blow it out or it creates nasal discharge to flush it out. Congestion is another way to get rid of it. They can look really similar.
The difference is in the case of a seasonal allergy, a slightly different part of the immune system is revving up than when the body is fighting a virus. With an allergy, the body releases histamine, which is a dominant part what causes itching. If there is itching of the nose or what we call the allergic salute, where you rub the nose, or itching of the eyes and a clear nasal discharge, that's more likely to be an allergy, especially in a family or in kids that have allergies.
A cold virus triggers white blood cells to be dispatched to the nose so a cold may start with a clear runny nose or sneezing. Fairly soon the discharge starts to get cloudy from the white blood cells or creamy or even green as the remains of white blood cells end up getting into the nasal discharge. A cold might have a low-grade fever too because the body's trying to kill the virus. Allergies do not cause a fever.
As a pediatrician I can often tell the difference by looking in the child's ears, nose and throat. The exam often looks quite different.
This may not help you decide if you should send your child to school or daycare today, but another way to determine if a child is suffering from a cold or allergies is the duration. A cold typically lasts about a week. A mild cold might resolve in five days. A more severe cold could last 10 or maybe even 14 day. If a congested, stuffy, runny nose doesn't go away by then, it’s time to start looking for an allergic connection.