Signs and Tests

History is important in diagnosing all allergies, including whether the symptoms vary according to time of day or the season and possible exposures that involve pets, diet changes, or other sources of potential allergens. Severe reactions often develop very quickly after exposure, such as eating culprit nuts or getting stung.

Testing may be required to determine if symptoms are an actual allergy or caused by other problems. For example, eating contaminated food "food poisoning" may cause symptoms that resemble food allergies. Some medications (such as aspirin, ampicillin, and others) can produce non-allergic reactions, including rashes, that resemble drug allergies but are not true allergies.

• Antibody/immunoglobulin (particularly IgE) levels that are elevated indicate a 'primed' immune system.
• The CBC may reveal an increase in eosinophils.
• Complement levels may be abnormal.
• Testing may reveal the specific allergen(s).
  • Skin testing is the most common method of allergy testing. This may include intradermal, scratch, patch, or other tests. Skin testing may even be an option for young children and infants, depending on the circumstances.
  • Occasionally, the suspected allergen is dissolved and dropped onto the lining of the lower eyelid (conjunctiva) as a means of testing for allergies.
  • Other testing to determine the specific causative allergen may include various types of "use" or "elimination" tests where suspected items are eliminated and/or introduced while the person is observed for response to the substance. This is often employed when foods or medications are being evaluated as possible allergens.
  • Tests for reaction to physical stimuli may include application of the stimuli (heat, cold, and so on) and observation for an allergic response.

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