Causes of Contact Dermatitis

Contact dermatitis is skin inflammation that results from contact with certain substances. There are two types of contact dermatitis: irritant and allergic. The cause of your contact dermatitis depends on what type it is.

Irritant contact dermatitis is caused by contact with substances that actually irritate the skin. You may encounter these substances at work or at home. This type of contact dermatitis is common in certain professions, such as hairdressers, chemists, gardeners, and cement workers. Substances that can cause irritant contact dermatitis include:

  • acids
  • alkaline materials
  • fragrances
  • preservatives
  • soaps
  • detergents
  • solvents
  • any harsh chemicals

Allergic contact dermatitis is a reaction to a substance you are allergic to (an allergen). It is caused by your immune system’s response to the substance. When you contact an allergen, your immune system attacks it as though it were harmful. We don’t know what causes you to develop allergies.

More than 3,700 allergens have been identified. Fewer than 40 of these allergens cause the majority of cases of allergic contact dermatitis.

Poison ivy, oak, and sumac are the best-known plants that cause allergic reactions. Other allergens often associated with contact dermatitis are:

  • adhesives
  • cleansers
  • contact lens solution
  • cosmetics
  • detergents
  • dyes (for clothes, leather, cosmetics, or hair)
  • fiberglass
  • first-aid ointments or creams containing neomycin or bacitracin
  • formaldehyde
  • fragrances
  • gasoline
  • leather tanning agents
  • metal (especially nickel) jewelry
  • motor oil
  • nail polish remover
  • paints
  • preservatives
  • rubber (in clothing, shoes, gloves, etc.), especially latex
  • shampoo
  • soaps
  • sunscreen
  • toothpaste
  • varnishes

Sometimes allergic contact dermatitis occurs only after a substance is applied to the skin and then exposed to the sun. This is called photoallergic contact dermatitis. This is common with sunscreens and ointments containing NSAIDs (nonsteroidal anti-inflammatory drugs).

If you have any kind of allergy, you’re more likely to develop allergic contact dermatitis.

People with existing skin disorders such as eczema, psoriasis, acne, or others are also more likely to get contact dermatitis.

People who work with their skin in water on a regular basis are more likely to develop contact dermatitis. This is because the water strips the skin of protective oils. The same is true for people who work outdoors or with high levels of heat. People who commonly develop contact dermatitis include:

  • cooks and chefs
  • welders
  • glass blowers
  • farmers
  • factory workers
  • hairstylists
  • construction workers
  • healthcare workers
  • lifeguards

Women are twice as likely to have contact dermatitis as men. This is because women tend to work in jobs where contact dermatitis is more prevalent: hairdressing, nursing, etc.

Repeated use of irritants can also increase sensitivity to contact dermatitis. The first time you use something like contact lens solution or wear a watch containing nickel, you may have no response. Repeated use, however, can increase your risk for contact dermatitis symptoms.

Sunlight can also be a risk factor. Certain contact dermatitis allergens are photosensitizers; these only cause a skin reaction after they are exposed to sunlight. Common photosensitizers are: perfumes and aftershave lotions that contain certain oils; soaps, detergents, and sunscreens; and some fruits and vegetables, including limes, celery, and figs.