Contact dermatitis and patch testing for the allergist

Abstract

CD is a common inflammatory skin disease and should be suspected in patients presenting with acute, subacute, or chronic dermatitis. The gold standard for diagnosing allergic CD is a PT. This article provides practical recommendations for the diagnosis and management of CD commonly seen by the allergist in their practice.

A review of contact dermatitis

“…11,12,19 Mechanism Our current understanding of ACD is that of a 2-phase process that begins with sensitization with a low-molecular-weight allergen or hapten, which is presented by dermal dendritic cells (DCs) to T cells in a proximal draining lymph node. 1,2,20 The DCs involved in hapten recognition and pathogenesis are thought to be Langerhans cells, or myeloid DCs, which produce interleukin (IL)-1b. 1,21 The sensitization phase results in the production of effector T cells, which in the second phase, the elicitation phase, produce dermatitis, which develops approximately 72 hours after re-exposure to the offending allergen.…”

“…20 Other findings of ACD include spongiosis and intraepidermal vesicles, in which clusters of T cells and DCs have been identified in the dermis beneath these lesions. 1,2…”

“…Contact dermatitis (CD), or dermatitis attributed to "outside" allergens or irritants, is a skin disorder often attributed to occupational skin exposures making it the most common occupational skin disease. 1,2 Apart from occupational exposures, the increased and frequent use of cosmetics and personal care products is an additional risk factor for the development of CD, particularly in women. 3,4 The use of multiple cosmetic products has become a widespread trend, with the advent of "influencers" promoting the use of multiple cleansers and products such as double-cleansing and 10-step skincare routines, which result in increased exposure to sensitizers.…”

Art of prevention: The importance of feeding traditions

“…Irritant CD (ICD), which accounts for 80% of all CD cases, is most commonly caused by rapid and repeated wet-to-dry cycles, but irritation from substances such as saliva, soap, and wipes also plays a role. The remaining 20% of CD cases are due to allergic CD (ACD), a type IV delayed hypersensitivity reaction that occurs after sensitization and subsequent exposure to a specific allergen (Esser and Martin, 2017, Fonacier and Noor, 2018). Protein CD refers to an eczematous dermatitis that results from cutaneous exposure to protein, typically in foods (Renz et al, 2018).…”

“…Protein CD refers to an eczematous dermatitis that results from cutaneous exposure to protein, typically in foods (Renz et al, 2018). Thought to be a Th2-skewed, mixed type I and type IV hypersensitivity reaction with downstream generation of antigen-specific immunoglobulin E, protein CD presents as acute pruritus or stinging within minutes of skin exposure on a backdrop of chronic eczema (Brancaccio and Alvarez, 2004, Fonacier and Noor, 2018, Hjorth and Roed-Petersen, 1976, Janssens et al, 1995). Sensitization requires either pre-existing ICD or irritation from the sensitizer itself.…”