What is Contact Dermatitis?

Dermatitis, also known as Eczema, refers to a group of disorders which share similarities in clinical appearance and biopsy findings, but may have different causes. Eczema originates from a Greek word meaning "to boil". Acute dermatitis often appears vesicular, or tiny water blisters, whereas chronic dermatitis may be red, scaly, and thickened. Itching is a common symptom of all types of dermatitis.

Contact Dermatitis

The two major types of contact dermatitis are irritant contact dermatitis and allergic contact dermatitis and these two commonly co-exist. For example, contact allergy to a glove chemical may occur in an individual with irritant hand dermatitis due to harsh soaps used for hand washing. Common allergens include urushiol (e.g. poison ivy), nickel (e.g. in jewelry, cell phones, watches), fragrances, preservatives, topical antibiotics (e.g. neomycin, bacitracin) and paraphenylenediamine (e.g. black hair dye). Common irritants include water, soap, and solvents.

Allergic Contact Dermatitis

Dermatology Contact Dermatitis Hand Closeup Photo

The most common allergen causing allergic contact dermatitis in the United States is urushiol, found in poison ivy, oak and sumac. Of individuals patch tested by specialists in North America, the most common allergens include:

  • Metals (e.g. nickel, cobalt, chromate, gold)
  • Fragrances (e.g. fragrance mixtures)
  • Preservatives (e.g. quaternium-15, methylisothiazolinone)
  • Topical antibiotics (e. g. neomycin, bacitracin).

Cause: Allergic contact dermatitis is a cell-mediated, delayed, Type IV allergic reaction, resulting from contact with a specific allergen to which a patient has developed a specific sensitivity. Clinical manifestations usually occur within hours to days after allergen exposure. After removal of the allergen, allergic contact dermatitis typically persists for up to three weeks.

Clinical Presentation: The patient usually complains of an intensely itchy rash at the site of contact with the allergen.

Exam: Acute allergic contact dermatitis classically presents as small red bumps and water blisters. Chronic allergic contact dermatitis may present as dry, scaly, fissured and thickened skin. In general, allergic contact dermatitis occurs at the site of contact with the allergen; nickel allergy usually results in dermatitis underlying nickel-containing objects, (e.g. jewelry - earlobes, neck, wrists; belt buckles – umbilicus; cell phones – cheeks). However, dermatitis in certain sites, especially the eyelids and face, may result from contact to allergens on the hands (fingernail polish) or scalp (hair products).

Lab Tests: Skin biopsies are usually not diagnostic and are only helpful to rule out other conditions such as psoriasis. Skin scrapings for fungus or a scabies preparation will rule out those conditions.

Diagnosis: The key features of allergic contact dermatitis are itchy water blisters or scaly, thickened skin that correspond to the area of contact with the allergen.

Dermatology Contact Dermatitis Neck Closeup Photo

Itching should always be present for allergic contact dermatitis. The responsible allergen is identified by patch testing. Patch testing typically occurs over 5-7 days. On the first day, allergens are applied to the upper back and taped in place. After about 2 days, the patches are removed and locations marked. The patch sites are read by the clinician at 2 days and 5-7 days. Allergic reactions result in raised, pink-red reaction with small bumps or water blisters at the patch site. After identification of the allergen by patch testing, clinical relevance is determined by evaluating potential exposures to the allergen (identifying the ingredient in the patient’s products used in the location of dermatitis). If the dermatitis clears after avoidance of the allergen, this is good evidence that the patch test reaction is clinically relevant. Improvement of allergic contact dermatitis typically requires at least 3 weeks and often up to 2 months of allergen avoidance.

Management: After identification of allergens through patch testing, customizable lists of allergen-free products (CAMP – Contact Allergen Management Plan), and other helpful resources are available through the American Contact Dermatitis Society website. Mid-potency to high potency topical corticosteroids are helpful. Restoration of the skin barrier includes mild soaps and moisturizers. An acute flare of widespread and extensive allergic contact dermatitis will respond to a three-week tapering course of systemic corticosteroids. A standard adult dose consists of 40- 60 mg of prednisone daily for one week, followed by a tapering dose over the next 2 weeks. Treatment with less than 3 weeks of oral prednisone is insufficient and will usually result in rebound dermatitis.

Patient Information: American Contact Dermatitis Society

Irritant Contact Dermatitis

Irritant contact dermatitis is the most common form of contact dermatitis. Occupations at high risk include those involving repeated exposure to water and/or soap (wet work) such as health care workers, janitorial services, and food industry employees or those involving exposure to solvents such as machinists.

Cause: Irritant contact dermatitis is a non-allergic response to chemicals or physical agents such as friction which disrupt the normal skin barrier. Strong irritants include acids and alkalis, whereas weak irritants include soaps and cleansers. Damaged skin lacks the proper oils and moisture, thus allowing irritants to penetrate more deeply and cause further damage by triggering inflammation. Any condition that impairs skin barrier function, such as atopic dermatitis (childhood eczema) or dry skin is a risk factor for developing irritant contact dermatitis.

Clinical Presentation: Irritant contact dermatitis typically develops weeks after exposure to weak irritants such as hand soap or immediately after exposure to strong irritants such as bleach. Itching, pain, and burning are common symptoms.

Exam: Irritant contact dermatitis often appears in a well-defined area with a glazed appearance, but there may also be redness, swelling, blistering, fissuring and scaling. Initially, irritant reactions are usually confined to the site of contact with the irritant. The most common locations are hands, forearms, eyelids, and face.

Lab Tests: Skin biopsies are usually not diagnostic and are only helpful to rule out other conditions such as psoriasis. Skin scrapings for fungus or a scabies preparation will rule out those conditions.

Diagnosis: Irritant contact dermatitis is a diagnosis of exclusion. The typical patient presents with an itchy or painful dermatitis beginning approximately three months after low grade irritant exposure (e.g. hand dermatitis in a nursing student) or shortly after exposure to a strong irritant or frictional exposure.

Management: The management of irritant contact dermatitis consists of identifying and removing the irritant(s) and repairing the normal skin barrier. Mild soaps and moisturizers should be used. For irritant hand dermatitis, vinyl gloves should be worn as a barrier to unavoidable irritant exposures such as dish soap and juice from citrus fruits. Cotton gloves over a heavy emollient such as petroleum jelly overnight may also be helpful. Each water exposure should be immediately followed by application of an emollient to prevent evaporation of skin fluids. For cracks and fissures, application of superglue as a sealant may also be helpful. Mid potency topical corticosteroid may also be helpful.

Patient Information: National Eczema Association


Modified from Chapter 8 "Dermatitis" by Kristin Hook and Erin Warshaw in Clinical Dermatology (editors Soutor and Hordinsky)