Causes and Diagnosis of Allergic Rhinitis in Children

While nasal allergy (allergic rhinitis) is common in adults and adolescents, the same isn't true for very young children. This essentially comes down to two things: development and exposure.

An allergy, by definition, is related to a previous immune response—one in which an immune cell (antibody) is produced to defend against a perceived threat. The antibody remains in the body thereafter, ready to respond if the threat returns.

When it does, the ​immune system can sometimes overreact, triggering a cascade of symptoms commonly associated with an allergy. 

But babies and toddlers don't yet have a fully developed immune system, meaning their bodies don't reliably respond in this way just yet. Furthermore, their young age typically means they have had fewer opportunities to be exposed to allergens.

When cases do occur in children, they are typically in those over age 4. Though uncommon, it is possible for younger kids to develop allergic rhinitis too.

Allergic Rhinitis in Babies

Allergic rhinitis is a type of allergy that affects the nasal passages, causing congestion, runny nose, sneezing, and watery eyes.

Healthcare providers tend only to see the condition in children as they reach school age. Before then, allergies are mostly constrained to eczema (atopic dermatitis) or food-related allergies.

But that doesn't mean that allergic rhinitis never affects young children; it does.

By contrast, outdoor allergens are less commonly associated with rhinitis in babies simply because they haven't been around long enough to have experienced the pollen exposure needed to develop a seasonal allergy.

Confirming the Diagnosis

To differentiate between an allergy and other possible causes, a pediatrician will look at the accompanying symptoms. In most cases, a baby with allergic rhinitis would also have eczema, asthma, or symptoms of an adverse reaction to food, medication, or an insect bite.

If an allergy is suspected, the healthcare provider can order an allergy test to confirm the diagnosis. The skin test can either be performed by pricking the top layer of the skin with a diluted allergen (such as mold or pet dander) or by using a thin needle to inject the diluted allergen into the skin.

All told, it takes around 15 minutes for a positive result to process. The tests, while accurate, should never be used on infants under 6 months.

Other Possible Causes

While an allergy may be suspected, there are numerous other conditions that can mimic the symptoms of rhinitis, including an upper respiratory infection. Although a fever would typically accompany this, it can often be low-grade and hardly noticed.

Additionally, teething can cause an infant to have a runny nose, resulting in the accumulation of mucus and the development of congestion.

Adenoid hypertrophy (enlarged adenoids) is also a common cause of chronic congestion in younger children.

If nasal symptoms persist or worsen after treating a cold, flu, or infection, speak with your child's healthcare provider and ask for a referral to an allergist, ideally one specializing in pediatric allergies.