Risk Factors for Non-Allergic Chronic Rhinitis

The elderly are at risk for chronic rhinitis as the mucous membranes become dry with age. Women are at higher risk for rhinitis during pregnancy. (On the other hand, some women with chronic rhinitis may actually experience improved symptoms during pregnancy.) 

Risk Factors for Allergic Rhinitis

Family History. About 26 million Americans have seasonal allergic rhinitis and up to 40 million may have mild symptoms. It is the most common chronic condition in childhood. Genetic factors are the major determinants of allergies. If both parents have an allergy, the risk to the child is 75%. If one parent is allergic, the child's chances are 50%. Children with family members who are allergic are at highest risk, but allergies can develop in anyone.

Seasonal Effects. One study reported that the month of one's birth might influence the risk for allergies; those born in September, October, or November had the highest risk and those born in June, July, and August had the lowest. One theory to explain this observation is that infants born in the fall spend more time in the house during their first year of development and are, therefore, exposed to higher levels of house dust, an important allergen. Another study found that those born in winter months had an increased risk for allergies to house dust. The current climatic phenomenon, El Nino, which causes mild winters and heavy rains, may currently be making allergies worse by causing plants to pollinate earlier and increasing the incidence of molds.

Age. Although allergies often appear first in childhood, they may develop at any age. In some cases, allergies go into remission for years and then return later in life. People who develop hay fever in early childhood are likely not to have the allergy in adulthood. Those who develop it after age 20, however, tend to continue to have hay fever at least into middle age.

Affluence. Allergies and, even worse, asthma are on the rise. Theories to explain this increase point, ironically, to healthier as well as wealthier conditions in industrialized countries. A recent study in Germany that tracked East German children after the country became unified reported that children in the areas previously under communism experienced a significant increase in allergies -- particularly hay fever -- when they were exposed to a Western lifestyle. Included in lifestyle changes were increases in wall-to-wall carpeting, cat ownership, dampness in the home, and consumption of margarine (which has been associated with hay fever). Some scientists believe that children are overexposed to indoor allergens because they are now spending three hours or more indoors each day engaging in sedentary activities, including watching television, playing video games, or using a computer. This exposure is intensified by the recent trend of making homes more energy-efficient, which may result in more dust mites being trapped inside.

One theory blames childhood immunization against certain infectious diseases, including measles and whooping cough. When children develop these infections, the immune system releases helper T-1 (TH1) cells. These cells stimulate a number of infection-fighting immune factors and, at the same time, suppress cells called T-2 (TH2), which normally trigger antibodies that attack airborne allergens and parasites. Experts postulate that in some children who are vaccinated against childhood diseases, TH2 cells remain actively engaged against common allergens and, therefore, stimulate allergies. In families with many siblings, younger children are at lower risk for allergies, possibly because they are exposed to more infections.