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Regardless of whether a cold or allergy is suspected, physicians will usually begin with the patient’s medical history and a physical examination. If a cold or flu is suspected, the physician may recommend rest and a follow-up later if symptoms persist.

If sinusitis is suspected, physicians may recommend a sinus x-ray or CAT scan to produce an image of the sinus cavities.  A swab of throat tissue (culture) may be taken for testing if strep throat is suspected.

Allergy testing is more involved and may include one or more of the following tests to identify the specific allergen(s) involved.

• Skin tests. These tests are the most commonly performed allergy tests and are the least time consuming and expensive. Small amounts of the suspected allergen are introduced to the skin by scratching, pricking or puncturing the skin with a needle. A raised, red itchy bump on the area of the skin where an allergen was introduced indicates an allergy to that substance. Also, the greater the skin reaction, the more sensitive the patient is to that allergen. Skin tests are considered to be about 90 percent accurate.

  

• Blood tests. Blood tests use radioactive or enzyme markers to detect levels of IgE antibodies. These tests are useful if a widespread skin rash makes skin testing difficult, or if the patient has the potential for a sudden and severe allergic response to the test allergen(s). Blood tests are considered to be about 90 percent accurate.
  
  
• Elimination diets. An elimination diet is used to help isolate sensitivity to specific foods. The eight foods that most frequently cause allergies (soy, wheat, tree nuts, peanuts, milk, eggs, fish and shellfish) are not included in the initial diet. The patient stays on the prescribed diet for four to seven days. If the symptoms continue, additional foods are removed from the diet until the symptoms stop. Once the symptoms disappear, new foods are added to the basic diet, one at a time, until the symptoms reappear. The key to the success of the elimination diet is consuming pure foods. Many processed foods contain small amounts of common allergens, which can affect the accuracy of the elimination diet for diagnosing food allergies.