How can you tell if a runny nose is from a cold or from allergies? My husband and I both have allergies and I wonder if our two year old son has them too or just has been having a series of mild colds. - Tina, Ontario
The Pediatrician Answers:
Distinguishing between the "allergic" runny nose and a regular cold can be quite difficult. There is no blood test, and there are over 200 viruses that can cause colds, so it's just not feasible to test for cold viruses currently. Thus, most physicians have to rely on parents' reports of their children's symptoms and duration. The common uncomplicated cold should generally last about 7-10 days, whereas "allergic" noses tend to be runny for weeks. Allergic runny noses may also be more seasonal (for instance, pollen allergies tend to worsen in the spring and the fall).
The problem is, the average 2-year-old with a healthy immune system may get 8-12 colds a year, so it is sometimes hard to distinguish if your child truly has an allergy or just back-to-back colds. Color of discharge, sneezing, or cough are usually not very helpful.
Allergic children tend to have other associated symptoms such as watery or itchy eyes, or occasionally eczema (a dry skin condition). Finally, heredity certainly plays a role. If both parents have "allergic" runny noses, their children have about a 60% chance of also developing allergy symptoms. Some allergic runny noses may respond to antihistamine medicines such as diphenydramine (Benadryl), so a trial of medication may sometimes help in sorting out the sniffles.