Allergic Contact Dermatitis

Excerpt

Allergic contact dermatitis (ACD) is a type 4 or delayed-type hypersensitivity response (DTH) by an individual’s immune system to a small molecule (less than 500 daltons), or hapten, that contacts a sensitized individual’s skin. The initial or induction phase of ACD occurs when the hapten combines with a protein to form a complex that leads to the expansion of an allergen-specific T cell population; the name for this process is sensitization. During the elicitation phase, re-exposure to the antigen leads to the development of dermatitis. ACD accounts for 20% of contact dermatoses, and allergens differ greatly based upon geography, personal habits, and hobbies, and often, the types of preservatives that are legally permissible, such as quaternium-15 in the United States but not Europe.