The Occupational and Environmental Unit at Tri-Cities Hospital, in Dallas, Texas, is  the only hospital in the United States today where in-patient evaluations and treatments for environmental illness are performed. For most patients across the country the evaluation and treatment is performed on an out-patient basis. An environmental physician may use a number of options for evaluating illnesses to determine if they are caused or reinforced by allergies.

Elimination Diet: Often a doctor will suggest an elimination diet to detect food allergies. This involves eliminating the suspected food or foods from one's diet for at least ten to fourteen days with the hope that the symptoms disappear. Though these vary from person to person, the foods that most frequently cause a reaction are milk and milk products, wheat, yeast, corn, eggs, coffee, soy, potatoes, tomatoes, beef, pork, chicken, peanuts, oranges, chocolate, and sugar.

Skin Testing: Skin testing is a commonly used and fairly accurate means to test for allergies to pollens, and it is about 35 percent accurate for molds. Unfortunately, it is not a satisfactory way to accurately identify a patient's food allergies. The most commonly used form of skin testing is the scratch test, which is done on the surface of the skin. Many environmental physicians use intradermal testing (an injection into the outer layers of the skin) for dust, molds, and pollens, as well as foods and chemicals. The response to therapy based on the intradermal testing can be more rapid and the testing itself, in the hands of an experienced physician, is a safe procedure.

Provocation/Neutralization: This form of testing is used by many environmental physicians for testing foods and determining what may be an effective neutralizing (symptom-relieving) dose. Control of symptoms can be achieved by injecting small amounts of allergenic material intradermally or subcutaneously (just beneath the skin), or by placing a few drops of the allergenic material under the tongue.

RAST (Radio Allergo Sorbent Test): This blood test is used by many doctors in diagnosing their patients' allergies. RAST testing can be a means of diagnosing allergies to pollens, molds, dust, bee venom, and other allergens. RAST testing, however, is not very accurate in testing foods, and it can be expensive.

Electroacupuncture Biofeedback: One potentially useful but much less frequently employed method of testing utilizes electroacupuncture equipment to measure minute changes in the electrical conductance of the skin. Some clinicians claim that this method correlates extremely well with skin testing, is much faster, and avoids the pain and slight risk of an allergic reaction associated with injecting allergens into the skin. "Investigational device" permits have been granted to some practitioners by the FDA (Food and Drug Administration) in order to review the usefulness of these devices as a diagnostic tool.

Thyroid Function: Another important factor in allergic diseases is the functioning of the thyroid gland. An overactive or underactive thyroid can result in increased allergies, skin problems, fatigue, nervousness, gastrointestinal problems, sleeping too much or too little, gaining or losing weight, swelling, and various types of pain. Thyroid function needs to be carefully evaluated.