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Contact dermatitis
Make it clearer
Contact dermatitis is an eczematous inflammation of the skin. It shows up where something touched the skin, and there are two different forms with two different mechanisms.
The irritant form is the more direct one: a substance chemically damages the skin, and it is mostly the cells of the epidermis that release the mediators of inflammation. The skin is damaged the way wood is damaged by a solvent. The allergic form works differently. It is a delayed hypersensitivity, called type 4, against a contact antigen, that is, against an outside substance that the immune system learned to recognize earlier. In one, the substance damages the skin on its own; in the other, the skin reacts because it already knew the substance.
In the allergic form the work is done by the dendritic cells of the skin, sentinel cells that capture the antigen. They activate effector T cells, the white blood cells that carry out the response, and it is those T cells that produce the inflammation you see.
In brief
Contact dermatitis is an eczematous inflammatory skin disease, either irritant or allergic.
In the irritant form, mostly epidermal cells release inflammatory mediators in response to direct chemical damage; the allergic form is a delayed, type 4 hypersensitivity to contact antigens.
In one, the substance damages the skin on its own; in the other, the skin reacts because it already knew the substance.
In the allergic form, dendritic cells in the skin capture the antigen and activate effector T cells that produce the inflammation.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingContact Dermatitis, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated