Why some people are allergic to certain things while others are not can be a difficult topic to understand. For example, a dog can jump into your lap and, just like that, you will start to sneeze and your eyes will drip. All of this will force you to toss Fido aside in search of a tissue box. Meanwhile, your friend or neighbor experiences none of the above effects.
Why is this? There are three main reasons: inherited genes, environment and age.
It's in the Genes
Allergies can often be blamed on mom and dad. The tendency to become allergic is inherited, and the chances that you also will be allergic increase from about 50 percent when one parent is allergic to 75 to 80 percent when both parents have allergies.
Tell your friends you're "atopic," meaning that you have inherited the tendency to have an allergy.
(And hope that none of your friends know Greek, as "atopic" derives from the Greek word for "strange.")
But you needn't feel strange...or alone. The American College of Allergy, Asthma and Immunology (ACAAI) estimates that as many as 50 million Americans suffer with asthma, hay fever, or other allergy-related conditions.
So, the family genes are stacked against you. Does this mean instant sniffles? Not always. Don't forget, even if you have a 60 percent chance of developing allergies, you also have a 40 percent chance of not developing them. That's why Fido turns your nose and eyes into streams while your brother is pretty much dry. In the genetic roll of dice, he came out the winner.
Environment Counts ...
There's more to developing allergies than heredity. What you become allergic to is based on when and how much you're exposed to a substance and how much of it you're exposed to.
For example, say you have a tendency to be allergic to mold spores. You may have no allergy symptoms when you're living alone in your spic 'n' span apartment, but when a roommate moves in, bringing along a jungle of house-plants, an old mattress, and a humidifier (to keep her skin moist) you soon become a symphony of sneezes and snorts. What happened? You had endured a certain amount of exposure to mold spores without a problem, but once the scales were tipped by the onslaught of your roommate's mold-bearing stuff, your immune system kicked into high gear.
... As Does Age
How old you are when you're exposed is critical, and viruses may also play a role. Recent studies show that heavy exposure early in life -- before age 2 -- may be protective against animal allergies and asthma.
Now that we've discovered the source of allergies and what makes certain people susceptible to them, it's time to look at specific types of allergies. First up is the most common type of allergy -- allergic rhinitis.