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Allergic contact dermatitis (Type IV hypersensitivity)

Created: 2/4/2004
Updated: 13/10/2008
 

Delayed Type IV hypersensitivity

Allergic contact dermatitis (ACD) is a specific immune response of sensitised lymphocytes to chemical additives contained in latex products. This response is known as delayed Type IV hypersensitivity. 

Delayed hypersensitivity reaction
 
T cells can cause tissue injury if they inappropriately react with self-antigens, or if they react to foreign antigens chronically associated with the body's own cells and tissues. Unlike Types I, II and III hypersensitivity reactions, antibodies are not involved.
 
The two patterns of T cell-mediated injury are:

i] Delayed type hypersensitivity (DTH) reactions

These are mediated by CD4 helper T lymphocytes. Injury results from the hydrolytic enzymes and toxic oxidants secreted by macrophages activated by CD4 lymphocytes. Later, chronic inflammation and fibrosis dominate the clinical picture. The nature of the event triggering the immune response is unknown.

Clinically at the outset, there may be an acute eczematous dermatitis on the dorsum of the hands, often with vesicle formation. The lesions typically appear 48-96 hours after exposure. Subsequently, the skin may become dry, crusted and thickened. Aetiological agents involve chemical additives, such as accelerators or antioxidants. Thiurams and carbamates are commonly implicated agents, but ACD can potentially occur in response to any latex chemical additive.

Allergic contact dermatitisContact dermatitis may be involved in latex sensitisation. Irritant or allergic contact reactions reduce the barrier properties of the skin and allow absorption of larger amounts of chemicals or proteins. This is thought to increase the risk of latex sensitisation. An increased frequency and progression through ACD may precede the onset of latex allergy. The use of either cotton liners for protection under the gloves, or non-latex gloves should reduce sensitisation and is recommended for individuals with irritant contact reactions or ACD.

ii] For Type I immediate hypersensitivity (see next page)



 


ArticleDate:20040402
SiteSection: Article
 
   
    
                                            
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