A cold... will progress and more symptom will present itself. And then in 7-10 days, it will end. This is a typical cold.
An allergy... will be watery eyes, sneezing, clear nose mucous... and will 'stop' if given kids Zyrtec or kids Claritin.
If symptoms still occur, even with Zyrtec, it is a cold.
Or, the Zyrtec does not work for her.... and so try another kids' allergy med, like Claritin.
For allergy meds... not all will work for everyone. For me, Claritin works, but it does not work for my Mom. So she takes Zyrtec. For me, Zyrtec does not work, and Claritin does.
I ONLY take the allergy meds, IF I get allergy symptoms.... ie: watery eyes, itchiness in my nose, sneezing, itchy eyes. I don't need to take Claritin everyday. I am allergic to any dust or pollen or things in the air, or days it is windy.
Kids in school, get sick a lot in the beginning.
If your child is coughing... and congested, this is typically a cold.