Patch Testing

Contact allergen testing is a simple and objective scientific method available to physicians to augment the diagnostic process. Often the contact allergen test response is the crucial piece of information that allows for the early identification of the offending allergen(s) and confirmation of a diagnosis of ACD.8 If physician and patient can determine how contact was made to the allergenic substance, the patient can then take appropriate action to avoid exposure to the allergen and, if possible, to substitute nonallergenic agents.

There are instances when a positive test response is indicative of an allergy not to the specific allergen tested but to a related, cross-reactive substance. For example, a positive test reaction to p-phenylenediamine may not only incriminate the dye itself, but it may also alert the physician to the possibility that a group of immunochemically related substances, such as local anesthetics that have an amino group in the para position, may need to be investigated as potential allergens.

Negative test results to contact allergen testing are also important to the diagnostic process. Negative test results help to rule out the most common allergens as the source of the persistent eczematous condition, which guides the physician's search for possible causes.

TRUE Test® is a ready-to-use contact allergen test for the differential diagnosis and management of persistent eczematous conditions. Routine early contact allergen testing with TRUE Test® can help resolve persistent eczema faster and economically.

TRUE Test® may also be used adjunctively to determine the presence of a contact hypersensitivity component in other long-standing and stubborn cases of dermatologic diseases, such as atopic dermatitis, seborrheic dermatitis, hypostatic eczema, dyshidrotic eczema, stasis dermatitis, and psoriasis.9-11

Pre-test Considerations

In persistent eczema, physical examination and history taking are important in establishing the presence of contact dermatitis and its possible causes. When the history and examination cannot exclude the possibility of contact dermatitis, contact allergen testing is indicated unless the dermatitis is obviously irritant in nature.

Important clues to the nature of the dermatitis can be obtained by noting the location of the skin inflammation. Inflammation on the legs, hands, arms, and other areas can provide important information as to the likelihood of an allergic or irritant origin. Morphologic nuances, including the presence of vesicles, erythema, pustules, round or irregular patches, and edema, can also be important in differential diagnosis.

Physical examination coupled with detailed history taking can often form the basis of a preliminary diagnosis of ACD. However, only contact allergen testing can definitively establish the presence of ACD and identify the offending allergens.


Guidelines to History taking

A full and accurate history is particularly important in the evaluation of a patient suspected of suffering from contact dermatitis. It is recommended that the physician take the history personally, whenever possible. The notes below are included as an outline only and should be adapted or expanded, depending on the circumstances of each case.

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SmartPractice Denmark is located in Hillerød, 35 km north of Copenhagen in beautiful surroundings near the Frederiksborg Castle.
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