What are Some Common Causes of Contact Dermatitis?Along with the evaluation for contact dermatitis, which includes patch testing, a person’s history of exposure to various chemicals can help to determine the cause of the rash. The most common patch test performed in the United States is the TRUE test, and is the only test FDA approved for the diagnosis of contact dermatitis. Avoidance information is available for the chemicals tested for in this panel.
The most important aspect of the treatment of contact dermatitis involves avoidance of the trigger. Find out more about the treatment of contact dermatitis.
Occupational. Occupational skin diseases are second only to traumatic injuries as the most common cause of job-related diseases. Approximately 40% of Worker’s Compensation cases involve skin problems, and up to 95% of these involve job-induced contact dermatitis.
The most common jobs associated with contact dermatitis include:
- Health professions (latex allergy)
- Food processors
- Construction workers
Contact dermatitis of the hands is the most common location of disease, and common causes include:
Plants.Plants from the Toxicodendron family is the most common cause of allergic contact dermatitis, and includes poison ivy, poison oak and poison sumac. The rash from these plants results in a linear, or streak-like, group of itchy blisters or bumps.
The chemicals released from the plants, called urushiols, cause the dermatitis. Urushiol can be carried on the fur of animals, garden tools, sports equipment and clothing. The smoke from burning Toxicodendron leaves can also carry urushiol.
Other plants related to Toxicodendron may contain urushiol, and cause a similar contact dermatitis. These include:
- Mango skin
- Cashew nut oil
- Gingko leaves
- Japanese lacquer
- Indian marking ink
Patch testing is not necessary for Toxicodendron plants, since this is diagnosis made with a consistent history and physical examination.
Other causes of plant contact dermatitis include contact with the Peruvian lily, a common cause of hand dermatitis in flower workers, as well as seasonal contact dermatitis from exposure to airborne pollens. Patch testing may be performed with these plants, and cross-reactivity with fragrances (on the TRUE test) is common.
Cosmetics. Cosmetic induced contact dermatitis is very common, since people may apply numerous chemicals to their skin, hair and scalp on a daily basis. Typically, the rash will occur on the skin where the cosmetic was applied, although sometimes the rash will occur on another part of the body (for example, reactions to nail polish may first cause an eyelid rash as a result of touching the eyelid).
Fragrances appear to be an important and common cause of contact dermatitis. Rashes can appear on the neck in a pattern consistent with spraying perfume on the area. Patch testing to fragrance mix, found in the TRUE test panel, can help identify the cause and provide important information on avoidance.
Avoiding fragrances can be difficult, and use of products labeled “unscented” can be misleading, as a masking fragrance may be added. It is better to use products labeled as “fragrance-free”, and are typically tolerated by people with fragrance-induced contact dermatitis.
Hair products are another common cause of contact dermatitis. Common chemicals include phenylenediamine in hair dyes, cocamidopropyl betaine in shampoos and bath products, and glyceryl thioglycolate in permanent wave solution. Of these, only phenylenediamine is tested for in the TRUE test panel.
Reactions to acrylic coatings on fingernails are a common cause of contact dermatitis on the fingers, as well as on the face and eyelids. Many people who use cosmetics on their fingernails (artificial nails or coatings on natural nails) may touch their face and eyelids with their nails. Common chemicals include acrylates and formaldehyde-based resins.
Sunscreens and sun blocks, also commonly found in various moisturizers and cosmetics, can result in facial contact dermatitis, with or without activation by sunlight. Some of the “chemical-free” sunscreens, containing physical blocking agents such as zinc oxide and titanium dioxide, are better tolerated by people with sunscreen-induced contact dermatitis.
Topical Medications. Numerous topical medications can result in contact dermatitis when applied to the skin. These include:
- lanolin, found in some moisterizers such as Eucerin
- topical antibiotics such as neomycin (Neosporin) and bacitracin
- para-aminobenzoic acid (PABA), found in some sunscreens
- anti-itch creams containing local anesthetics
- topical corticosteroids, such as hydrocortisone cream
- topical NSAIDs, such as Aspercreme