Allergies
Alternative names:
allergic response
Symptoms:
Note: Allergies vary according to the type of antigen and the part of the body in which the allergic reaction occurs.
Signs and tests:
History is important in diagnosing 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 allergens.
Testing may be required to determine if symptoms are an actual allergy or caused by other problems. For example, contaminated food ("food poisoning") may 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 allergic reaction.
- 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.
- 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 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.
- Tests for reaction to physical stimuli may include application of the stimuli (heat, cold, and so on) and observation for an allergic response.
This disease may also alter the results of the following tests:
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