Donald V. Belsito

Concomitant positive patch test results with standard screening tray in North America 1985–1989

Responses to patch test substances may occur contemporaneously. Such simultaneous reactions may reflect concomitant sensitization to 2 dissimilar allergens to which concurrent exposure has taken place (e.g., ethylenediamine dihydrochloride and neomycin). It may occur when the individual has been exposed to only 1 of the substances and exhibits a response to other substances of similar chemical structure (i.e., cross‐sensitization such as between para‐phenylenediamine and benzocaine). Such simultaneous responses may also be chance occurrences, reflecting multiple sensitization or the result of altered response due to the “angry back syndrome”. This investigation established that such concurrence of response is not uncommon and adds further documentation to the literature of these associations in patch test responses.

The immunologic basis of patch testing

During the past decade much has been learned about the cell-mediated immune responses that result in allergic contact dermatitis. The complex interaction between the hapten, the Langerhans cell, the specifically sensitized T cell, and the various soluble mediators of cellular immunity have begun to be delineated. This article reviews the pathophysiology of allergic contact dermatitis. Clinical and physicochemical modulators of this response, such as patient age, the anatomic site of antigenic challenge, and prior treatment with UVB, PUVA, glucocorticoids, or cyclosporine (Cyclosporin A), are stressed. The implications of these findings to the techniques of patch testing are summarized.

Reversal by lymphokines of the age-related hyporesponsiveness to contact sensitization and reduced Ia expression on Langerhans cells

SummaryContact sensitivity responses were evaluated in young adult (3–5 months) and aged (16–26 months) BALB/c mice which were systemically treated with interleukin-2 (IL-2), interferon-γ (IFN-γ) or saline. Mice older than 16 months of age have deficient numbers of Ia+ Langerhans cells in addition to their well-known impaired T cell functions. They also have an impaired cell-mediated response to contact sensitization with 1-chloro-2,4,6-trinitrobenzene. This hyporesponsiveness in aged mice can be almost completely reversed by ness in aged mice can be almost completely reversed by IL-2 and is marginally improved by IFN-γ. Exposure of skin from aged mice to interleukin-2 or interferon-γ, both in vivo and invvitro, causes increases in the density of Ia+ Langerhans cells to levels approximating those in young mice. Since IFN-γ causes partial restitution while IL-2 fully restores the contact hypersensitivity in aged animals, we conclude that the hyporesponsiveness in aged mice results both from defective Ia antigen expression on the antigen-presenting Langerhans cells and from deficient T cell function.

A SHERLOCKIAN APPROACH TO CONTACT DERMATITIS

Identifying the etiology of allergic contact dermatitis requires detective work. Not all allergic reactions are eczematous in appearance. The most reliable clinical clue to the allergic nature of the dermatitis is its geographic distribution. Patch testing provides the list of culprit allergens. The mystery is solved when the suspected allergen is found to be relevant and the patient has been adequately instructed in allergen avoidance.

Contact urticaria from pentamidine isethionate

2. Garioch J, Todd P, Lamey P J, Lewis M, Forsyth A, Rademaker M. The significance of a positive patch test reaction to mercury in oral disease. Contact Dermatitis 1990: 23: 301. 3. Fisher A A. Contact dermatitis, 3rd edition. Philadelphia: Lea & Febiger, 1976: 778-783. 4. Mobacken H, Hersle K, SJoberg K, Thilander H. Oral lichen planus: hypersensitivity to dental restoration materials. Contact Dermatitis 1984: 10: 11-15. 5. Laine J, Kalimo K, Forssell H, Happonen R. Resolution of oral lichenoid lesions after replacement of amalgam restorations in patients allergic to mercury compounds. Br J Derm 1992: 126: 10-15. 6. Lind P 0. Amalgam-related oral lichenoid reactions. Scand J Dent Res 1986: 94: 448-451. SHORT COMMUNICATIONS