Differentiating between irritant and allergic forms, and making the correct diagnosis, is important since different treatment options exist for either one. Clinical studies may take up to six weeks before results for a clear diagnosis are available. In ideal situations, confocal laser scanning microscopy can deliver a result within 24 hours. In conjunction with a patch test, it is then possible to determine and successfully avoid the irritant or allergen in question. VivaScope® devices are tools supplementing differentiation and enabling prompt and non-invasive monitoring.
The early symptoms of irritant contact dermatitis are a disruption of the superficial epidermis, followed by an inflammatory reaction. The confocal image generated by VivaScope devices depicts the disruption of the stratum corneum – the clear sign of irritant contact dermatitis.
While the symptoms of the irritant variant progress top-down (first visible by problems of the horny layer), allergic dermatitis progresses exactly the opposite way – from the bottom up (vesicles in the spinous layer).
The onset of allergic contact dermatitis is preceded by sensitization to an allergen. The confocal images illustrate that allergic dermatitis tends to exhibit early signs of spongiosis and oedema, whereas irritant dermatitis, on the other hand, does not exhibit these characteristics until much later.
 Astner S, Burnett N, Rius-Díaz F, Doukas AG, González S, Gonzalez E: “Irritant Contact Dermatitis Induced by a Common Household Irritant: A Noninvasive Evaluation of Ethnic Variability in Skin Response.” J Am Acad Dermatol. 2006; 54(3): 458-65.
 Astner S, Gonzalez E, Cheung A, Rius-Diaz F, González S: “Pilot Study on the Sensitivity and Specificity of In Vivo Reflectance Confocal Microscopy in the Diagnosis of Allergic Contact Dermatitis.” J Am Acad Dermatol. 2005; 53(6): 986-92.
 Astner S, Gonzalez E, Cheung A, Rius-Díaz F, Doukas A, William F, González S: “Non-Invasive Evaluation of the Kinetics of Allergic and Irritant Contact Dermatitis.” J Invest Dermatol. 2005; 124(2): 351-9.