Allergic Contact Dermatitis
Allergic contact dermatitis (ACD) is an inflammatory dermatosis resulting from Type IV, T cell-mediated delayed hypersensitivity reaction. ACD can present as both an acute and chronic. The most important step in the management of ACD is suspecting it may
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Tanja Bohl
18.1 Introduction Allergic contact dermatitis (ACD) is an inflammatory dermatosis where the tissue damage is the result of a Type IV, T cell-mediated delayed hypersensitivity reaction [1–9]. It is less common than irritant contact dermatitis (ICD) that is responsible for 80% of all contact dermatitis of the vulva. Vulvar contact dermatitis is common and of which 20% is due to ACD. Once acquired, the sensitization persists for life. It is not amenable to desensitization as with antibody-mediated allergies (Type I, IgE acute hypersensitivity). Ultimately identification of the allergen by patch testing and complete avoidance is required to prevent recurrences.
18.2 Pathogenesis ACD involves the presentation of antigens applied to the surface of the skin; dendritic cells (Langerhans cells, LC) within the epidermis process these antigens producing a distinct protein. The LC migrate to the regional lymph nodes where they present this to T cells resulting in their activation into Th1cells. The Th1 cells migrate back to the area of allergen application
T. Bohl (*) Jean Hailes for Women’s Health, Clayton, VIC, Australia
and initiate an inflammatory cascade resulting in the dermatitis seen clinically. This occurs specifically in the areas of antigen application. The activated Th1 cells are antigen specific and long lived. Future antigen exposure will result in dermatitis in the site of new and previously exposed areas if they differ.
18.2.1 Allergenicity Allergenicity is the ability to produce an allergic reaction. Not all potential allergens are equal in this respect.
18.2.2 Number of LC In the Exposed Tissue The number of LC in the vulvar skin is similar to other body sites with respect to the hair and non- hair-bearing tissues.
18.2.3 Tissue Integrity The vulva is a unique area of anatomy comprising hair- and non-hair-bearing skin, mucous membranes, and multiple creases that can become reservoirs of perspiration, natural secretions, exfoliated epidermal cells, urine, and feces. These creases are warm and also undergo friction due to skin touching skin and tight clothing.
© Springer International Publishing AG, part of Springer Nature 2019 J. Bornstein (ed.), Vulvar Disease, https://doi.org/10.1007/978-3-319-61621-6_18
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These factors can increase the absorption of allergens and susceptibility to irritants. Atopy and a preexisting vulvar dermatosis are associated with a higher rate of positive results to patch testing.
18.3 Etiology Anogenital ACD is usually due to topical allergens applied directly to the area, secondary exposure of allergens that are finger borne (e.g., acrylates in nail varnish), and rarely oral allergen exposure. Both ICD and ACD can complicate dermatoses. This should be considered in all patients with a vulvar dermatosis that becomes recalcitrant to therapy or flares after a period of control. Vulvar skin is exposed to varying potential irritants and allergens through childhood, puberty, menstruation, sexual activity, reproduction, and ultimately meno
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