A child with a respiratory allergy may have a stuffy and/or runny nose, sneezing, itchy skin and eyes, and/or red, watery eyes. Needless to say, it can be very uncomfortable. Whether the condition is seasonal or chronic depends on the particular allergen involved. Seasonal allergies tend to be caused by pollen, so symptoms recur at about the same time every year, usually when the offending plant is in bloom. Hay fever is an example of a seasonal allergy. Spring hay fever is most often due to pollens from grass and trees, while hay fever in later summer and early fall is usually caused by sensitivity to ragweed pollen and molds.

Ongoing or chronic allergies are usually caused by factors that are present in the environment year-round, such as animal fur, dust, or feathers. Allergic rhinitis is a chronic inflammation of the mucous membrane lining the nasal passages that is caused by an allergic reaction. It is characterized by a stuffy, runny nose, frequent sneezing, and a tendency to breathe through the mouth A child's eyes may be red and watery. Headache, itchiness, nosebleeds, and fatigue may be secondary complications. Dark circles under the eyes (called "allergic shiners"), along with a puffy look to the face, are frequently seen. Infants with chronic rhinitis are frequently allergic to food, most often cow's milk Older children with constantly runny noses are often reacting to wool, molds, feathers, dust, animal dander, and/or pollen. In some cases, a chronic runny nose may not be the result of an allergic reaction, however, and should be distinguished from a more serious underlying illness, such as chronic sinusitis. This is a task best performed by a health care professional.

Whether symptoms occur seasonally or chronically, there is often a family history of allergies; many times a parent or grandparent of an allergy sufferer also had allergies. In the presence of an allergen, a child's immune system releases histamines and similar chemicals to fight what it perceives as an invader. These chemicals cause a string of reactions, including the swelling and congestion of nasal passages and increased mucus production. This is essentially a hypersensitive or overactive response by a child's body to an external stimulus. A growing child becomes more capable of fighting off infections as his immune system matures, and he may also outgrow allergies.

Allergies can also contribute to other chronic health problems, such as acne, asthma, bedwetting, chronic ear infections, eczema, irritability, and even difficulty maintaining concentration. Allergic reactions can occur immediately after exposure to the offending substance, or take days to surface. A delayed allergic reaction can make it more difficult to pinpoint the allergen.