Dr. Wilkinson observes that it is not only the specific allergens (substances causing allergic reactions) that need to be identified and treated. Underlying genetic and nutritional factors, as well as exposure to toxic substances, often predispose the patient to develop sensitivities to foods, chemicals, airborne allergens, and other materials. Doctors of environmental medicine emphasize the importance of a thorough environmental- and nutritional-oriented history, as well as a careful physical examination, in order to discover possible contributing factors to the patient's illness.                       Dr. Wilkinson, says that in a thorough evaluation of the chronically ill, the history and physical exam might suggest nutritional problems, the presence of parasites or yeast, thyroid or adrenal disorders, the effect of dental work, psycho-spiritual issues, and other important considerations.

  First af all, the environmental physician tries to answer the question: What are the underlying dietary and environmental causes of, and contributing factors to, my patient's physical and mental symptoms? 

  Physicians of American Academy of Environmental Medicine (AAEM) distinguish some of the factors that may contribute to an sensitiveness of the individual: 

  Heredity/Genetics: Sensitivity to dietary and environmental agents can  be linked to one's heredity. AAEM members recognize that a genetic predisposition to the development of allergies can be handed on through successive generations of a person's bloodline. The number of family members in that chain who experienced severe allergies appears to increase the likelihood of their descendants experiencing allergies as well, and at an earlier age.

  Poor Nutrition: A major cause of chemical sensitivity is poor or inadequate nutrition. A diet of refined, processed foods deficient in vitamins, minerals, enzymes, and other vital nutrients can severely impair the body's ability to function efficiently due to the increased levels of toxins such foods contain. Their ingestion can also result in an increase of free radicals (highly reactive destructive molecules), which can further predispose a person to allergic reactions.

  Infection: Sensitivities to allergens can also be developed following severe infection, whether viral, bacterial, parasitic, or fungal (candida). Candidiasis or parasites can cause chronicinflammation or irritation of the lining of the intestinal tract. This inflammation can lead to "leaky gut syndrome," in which bacteria, bacterial toxins, and partially digested foods are able to travel from the intestine into the bloodstream, causing an allergic or immune reaction.

  Chemical Exposure: Current research has shown that due to their toxic effect on the body, exposure to pesticides, herbicides, petrochemicals, and other chemicals in the food and water supply, as well as in indoor and outdoor air, can lead to the development of allergic reactions.

  Stress: Increased emotional or physical stress can also contribute to allergies in ways that are often both subtle and overlooked.

Some other factors which that can lead to allergies and sensitivity reactions: 

• Frequent use of antibiotics, steroids, and other medications
• Hormonal changes due to the menstrual cycle, aging, or surgery
• Glandular disorders such as low thyroid function, thyroiditis, and adrenal insufficiency
• Physical trauma such as accidents or surgery
• Electromagnetic disturbances of the environment
• Geopathic factors (harmful radiation from the earth)
• Dental amalgam fillings that contain large amounts of mercury and other dental involvements, such as infections under the teeth