T he thin-layer rapid use epicutaneous (T.R.U.E.) Test of 23 common allergens is a valuable, first-line screening tool used by many dermatologists. Although the test focuses on common allergens, frequent questions have arisen from colleagues and patients as to where exactly a specific allergen is derived or what products should be avoided by patients who are allergic to that allergen. With this in mind, this column was developed to provide more educational information about the T.R.U.E. Test allergens. A rich, interesting history accompanies each of the 23 allergens, and understanding these historic perspectives can help to better educate patients. Each column will also highlight appropriate products patients should avoid when they’re allergic to a specific allergen.

Categories to Consider
Allergic contact dermatitis is an important disease with high impact both in terms of patient morbidity and economics.

The contact dermatitides include allergic contact dermatitis, irritant
contact dermatitis and contact urticaria. Irritant contact dermatitis is the most common form, and it accounts for approximately 80% of environmental- and occupational-based dermatoses. Contact urticaria (wheal and flare reaction) represents an IgE and mast cell-mediated immediate-type hypersensitivity reaction that can lead to anaphylaxis — the foremost example of this would be latex hypersensitivity. While this is beyond the scope of this section, we acknowledge this form of hypersensitivity due to the severity of the potential reactions and direct the reader to key sources.1,2

The primary focus of this column is to highlight the educational component of allergic contact dermatitis.

Introducing the Patient
Recently, a patient that had tested positive to lanolin, which was discovered by an area physician who had used the T.R.U.E. test, presented to the University of Miami Allergic Contact Dermatitis Clinic. She brought with her the “read sheet” results, which had “wool-wax” circled. She presented to our contact patch-testing center to find out what wool-wax meant because she had been avoiding wool and Woolite but was still suffering from a pruritic eruption.

The History of Wool Wax
The history of wool wax dates back several thousand years to the ancient Greeks, who recognized that water in which wool had been washed contained a valuable substance. That
substance, wool wax, was an outstanding emollient. Many names have been attributed to wool wax, including Hyssopus, Oesypum, and the most common form Oesypus.

Over time, methods to refine wool wax into refined lanolin were developed. The early extraction process of wool wax was simply an early version of the modern foam flotation process. By pouring the wool washings from a height into a receptacle, the wool wax formed froth that was skimmed off and allowed to collapse, separating the wool wax to the surface.

Technical advancements included “acid cracking,” which destabilized the wax and separated the wax into a lower sludge state that can be filtered. A later refinement was the addition of metals in the trivalent state to act as effective coagulants. Yet, it was the centrifugal separator that brought the extraction procedure into the new millennium, and this has become the preferred modern method of extraction.3

Testing for Lanolin Sensitivity
Patch testing for lanolin allergy can be accomplished with the T.R.U.E. test (site #2). The T.R.U.E. test is the commercially available, globally used, allergen screening system. While it is widely used, the discrepancy in allergen prevalence and uncertain relevance have led to scrutiny of its utility. The T.R.U.E test contains 23 allergens and one negative control. At best, this test is a minimum screening tool, as it tests only 23 of the more than 3,700 possible allergens that can cause allergic contact dermatitis.

Krob et al. recently demonstrated through meta-analytic techniques that nickel, thimerosal, cobalt, fragrance and balsam of Peru are the most prevalent allergens detected by the T.R.U.E. test. They go on to explain that a significant number of relevant allergens, not
present on the T.R.U.E. test, would potentially be missed by this screening tool alone.5
However, we are faced with important workforce economics: There are roughly 10,000 U.S. members of the American Academy of Dermatology, and many of these dermatologists serve remote locations. In contrast, there are approximately 450 members of the Allergic Contact Dermatitis Society (ACDS) (www.contactderm.org). Providing that everybody practiced, there would be roughly one ACDS member patch testing for every 22 dermatologists, and that would be if the distribution was evenly cast, which is not the case.

Thus, the T.R.U.E test is a basic and necessary screening tool that should be used and its limitations understood. Comprehensive patch testing and patch test support should be available to the general dermatologist and mechanisms are in place (such as the ACDS mentorship programs). Additionally, patient education materials are available through the Allergic Contact Dermatitis Society’s newly developed Contact Allergen Replacement Database (C.A.R.D).

The Value of This Patient Case
Our patient underscores the importance of appropriate patch testing — in conjunction with subsequent patient education. She unwittingly continued to be exposed to lanolin-wool wax and worsened her allergic contact dermatitis, despite having been T.R.U.E. tested. Once an allergen is identified, patient education is of the utmost importance because the mainstay of treatment
for allergic contact dermatitis is avoidance.