My 5-year-old daughter started to have a runny nose but has no other symptoms and her overall condition is good. Is it possible that it's just a common cold?

Yes, it is possible that your 5-year-old daughter simply has a cold if she only has a runny nose and no other symptoms. Cold symptoms can vary in severity, and not all cases involve a fever. To help her breathe better, you can try using saline water and a nasal bulb syringe to clear out any mucus. If her breathing does not improve within a few days, you may want to consider using a product like Sinus Rinse™ to help alleviate congestion.