While scientists don’t completely understand why allergies develop, they do believe that a combination of things create the immune system confusion, from genetic predisposition to environmental factors.
There are two main categories of risks that can contribute to the development of allergies—those that you can't change, and those that you can. Because you can't control whether or not you develop allergies, the line between uncontrollable risks (which are out of your control) and controllable factors is grey. Many things that may prevent allergies need to occur at a very young age.
Uncontrollable Risk Factors
These variables are out of your control. Although you can’t do anything to change them, it’s important to know if you are at risk.
Your family history. While sensitivities to specific allergens are not inherited, the tendency to develop allergies can be traced back to your parents. If your mother was allergic to dust mites for example, you might also develop allergies—but not necessarily to the same substance. If one of your parents had allergies, you have a one in three chance of also developing an allergy. This risk jumps as high as 75% if both of your parents had allergies.
Your age. Because repeated exposure to substances can prompt an allergic reaction, you are more likely to develop allergies as you get older.
Your immune response. The reactions of your immune system are out of your control. Once your body becomes sensitive to a substance, your immune system will produce larges amounts of antibodies to fight what it sees as a dangerous intruder. The type of antibody most commonly found in allergic reactions is called Immunoglobulin E (IgE), but your body can produce a unique antibody for every type of allergen.
Your Environment. Generally speaking, developed countries have much higher incidences of allergies than developing areas of the world. Scientists believe that the clean and sanitized homes of the industrialized world are actually detrimental to the immune system, and that exposure to illness-causing bacteria is necessary for the immune system to function optimally. When your immune system is not challenged by natural foes, it malfunctions and becomes supersensitive to seemingly harmless substances.