The Causes of Allergies

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.

Controllable Risk Factors

There are no controllable risk factors for adults who wish to decrease their risk of developing allergies, because allergy development isn't related to lifestyle habits. Intervention needs to occur early—during infancy and childhood. The following risk factors are considered uncontrollable for adults, but you can keep them in mind if you want to intervene to prevent your child from developing allergies.
  • Infancy Exposure to Breastfeeding. Exclusively breastfeeding your baby for at least six months can greatly reduce her risk of developing food allergies later in life.
  • Childhood Exposure to Bacteria. Early exposure to common household microbes, environmental bacteria, fermented foods, and probiotics (healthy bacteria from foods like yogurt and unpasteurized milk) may reduce a child's risk of developing allergies as she gets older.
  • Childhood Exposure to Antibiotics. Early exposure to antibiotics seems to disrupt the balance between harmful and helpful bacteria in the body, confusing the immune system and therefore increasing a child's risk of developing allergies. Avoiding unnecessary antibiotics may also reduce the risk of developing food allergies.
  • Childhood Exposure to Allergens. When a child is exposed to common allergens (such as dust mites and mold) early in life, she has a lower chance of developing allergies to these substances. Without exposure to these common allergens, a person may develop an allergic reaction to them later in life since they are unfamiliar to the immune system.
  • Childhood Exposure to Pets. The presence of an animal in the home, especially during the first year of life when the immune system is still developing, has been associated with a decreased risk of allergies to pet dander, as well as to other allergens such as molds and dust mites. In European studies, infants who were exposed to dogs or cats at home had only half as many allergies as children in pet-free homes.
  • Childhood Exposure to Secondhand Smoke. Children are at special risk of lung damage and illness from inhaled secondhand smoke. Children of parents who smoke are also at an increased risk for other respiratory illnesses, such as asthma.
While most risk factors for allergies are out of your control, it is possible to reduce your allergy symptoms by limiting your exposure to known allergens. Healthy eating habits and exercise can further strengthen the immune system and help avoid unwanted reactions.