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What is Contact Dermatitis?

It is a skin lesion resulting from contact with a foreign substance. In most cases an inflammatory skin rash called eczema is produced.

What types are there?

There are 2 types of Contact Dermatitis: Irritant and Allergic.

  • Irritant Contact Dermatitis: caused by the direct contact of an irritant substance. Irritant dermatitis occurs more frequently in certain professions, such as hairdressing, cleaning, metal industries, construction workers etc. It is not due to an allergic mechanism and it is universal. The most common part of the body where dermatitis occurs is on the hands.
  • Allergic Contact Dermatitis: Accounts for between 5 and 15% of all dermatoses. Inflammation of the skin occurs. It is a hypersensitivity reaction to a particular substance or group of related substances. Previous exposure to the substance is required to sensitize and subsequently the allergic reaction is produced. A personal predisposition is produced to these allergens.

Clinical Manifestations

Symptoms vary depending on the cause and if the dermatitis is caused by an allergic reaction or an irritant.

Allergic reactions can occur suddenly or after months of exposure to a substance.

In both types of Contact Dermatitis, we can see the following symptoms:

  • Red rash: This is the usual reaction. The rash appears immediately with Irritant Contact Dermatitis; in Allergic Contact Dermatitis, a rash may appear 24-72 hours after exposure to the allergen.
  • Blisters: Blisters and hives often appear where the skin was directly exposed to the allergen or irritant.
  • Itching: Irritant Contact Dermatitis tends to be more painful than itchy, while Allergic Contact Dermatitis often itches more.


The diagnosis of Contact Dermatitis is going over the patients history along with a Patch Test.

Patch Tests: The substance that is believed to be causing the problem is applied on the top part of the patients back for a period of 48 hours to see the reaction of the skin.

Once removed, there should be a first reading at 48 hours and a second at 72-96 hours, although sometimes it can be even later depending on the substances.

What are the substances most frequently involved in Contact Dermatitis?

The substances that most commonly cause Contact Dermatitis are:

  • Nickel:Jewelry, eyeglass frames and belt buckles.
  • Mercury: Especially by direct contact with antiseptics (mercurochrome) and broken thermometers.
  • Balsam of Peru: Some cosmetics have this.
  • Tires: Although the sources of contact are countless, perhaps the most important is the use of running shoes.
  • Cosmetics Perfumes
  • Potassium dichromate: Usually after contact with dyed skins (shoes, coats, chrome objects, etc).
  • Cobalt: Contained in paints and crayons, metal objects, etc.
  • Wood tar: Mainly used in creams and ointments.
  • Benzocaine: Used for children as a topical anesthetic and also to relieve itching.
  • Neomycin: Used as an antibacterial agent in many creams for burns and even skin infections.

Treatment of Contact Dermatitis

Treatment includes:

  • Wash with water to remove any trace of the irritant that may remain on the skin.
  • Use emollients (moisturizers).
  • Use of topical corticosteroids.
  • Use of oral corticosteroids or injected if necessary.
  • Remove the irritant or allergic substance. An experienced dermatologist will ask the patient several questions to detect the substances or antigens responsible for the allergic reaction.

Doctor Pablo Umbert

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