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Contact dermatitis

What is it?

It is an inflammatory reaction that occurs due to skin contact with an irritating agent (primary irritant dermatitis) or an agent that causes allergy (allergic dermatitis).

The primary irritant dermatitis occurs by direct action of the substance on the skin that damages it and triggers the reaction. It can be:

  • Acute: if the provocative substance has high concentrations and the response is immediate after exposure. This is the case of skin contact with strong acids.
  • Chronic: when skin is exposed repeatedly to low concentrations of irritating substances, causing cumulative damage. This is the case of eczema of the hands of people who deal daily with soap and detergents (housewives and kitchen professionals).

The allergic dermatitis occurs when an allergenic substance (which causes allergy) comes in contact with skin, and binding to proteins of the skin, begins to be recognized as foreign to the body, triggering an immune response to fight against it.

Characteristics and symptoms

Typical characteristics of contact dermatitis in the acute phase are redness, swelling, blistering and exudation. Later, there is the formation of crusts and scaling (sub-acute phase).

In a later phase, when it becomes chronic, appears to lichenification (thickening of skin, that gets rough). Pruritus (itch) is present at all stages, and can be mild or very intense.


The treatment of contact dermatitis depends on the type of contact (irritant or allergic) and the stage of it (acute, sub-acute or chronic), varying according to each case and should be determined by a dermatologist. Medications of local and oral use, like antihistamines and corticosteroids, are intended to decrease the inflammation and itching, which is often very intense.

Avoiding contact with substances that trigger the dermatitis is fundamental to the success of treatment. In the case of allergic eczema, a contact test may be helpful to find out what is causing the allergy. It is performed by placing 20-30 major allergenic substances in contensores that are left in contact with the skin for 48 hours. Those that trigger reaction should be avoided.

Related articles

- Atopic dermatitis
- Dyshidrosis

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