Daily Health Care

What causes contact dermatitis?

Irritant

The irritating substance causes direct damage to the morphological or functional integrity of the skin. It may be acute or chronic.

Acute exposure to a single chemical irritant potent causes an acute dermatitis. This can occur within minutes or after a few hours of exposure.

The process is:

- The substance penetrates the skin irritant.

- The substance damages the cell membrane.

- The damage of the cells promotes the release of chemicals that induce inflammation (inflammatory mediators) such as prostaglandins, histamine and kinins.

- Some inflammatory mediators cause increased blood flow to the area, while others attract additional inflammatory mediators.Feature: It is caused by cumulative effect of multiple low-level exposures to various irritants, but also contribute several cofactors such as weather or mechanical friction. This dermatitis may appear after several months or even years of contact with the substance.

The process is:

- Each exposure produces a gradual damage of the outer layer of skin.

- The top layer of skin (epidermis) is hardening.

- The fat layer of the skin is damaged gradually.

- The skin loses its protective function and increase the exposure to irritants that cause harm.

- There is a vicious cycle whose end result is the dryness, scaling and hyperkeratosis (thickening of the outermost layer) of the skin.

Allergic

It is caused by a type of immune reaction known as type IV or delayed hypersensitivity reaction cell. The characteristic feature of this immune response is a delay between exposure to the allergen and the subsequent reaction. There are two phases: sensitization and provocation.

Sensitization: when the allergenic substance penetrates the skin for the first time there is a cell-mediated immune response, which ends with the appearance of T lymphocytes sensitized to the allergen.

Provocation: Once sensitization has occurred, the new exposure to the allergen causing the proliferation and activation of T lymphocytes sensitized to it. Inflammatory mediators are released and produces inflammation and more cells are attracted to the area of ​​exposure. This process of immune reaction causes eczema in the affected area. Occurs between 12 – 96 hours after exposure. Small amounts of allergen can be enough to cause an inflammatory reaction.

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