Contact Dermatitis

Leslie Stewart, M.D.

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Causes of Contact Dermatitis... Irritant or Allergen?... Patch Testing... Prognosis... Patch Testing Statement ... Treatment and Prevention... References... Additional Reading... Faculty

Contact dermatitis is the most common occupational skin disease (OSD). The results of several studies have demonstrated that more than 90% of cases of OSD are contact dermatitis, and the vast majority of these cases involve a hand eruption. Hand dermatitis, also referred to as hand eczema, is a rash on the hands, characterized by scaling, redness, and itching.

Environmentally-caused skin diseases are in no way limited to the workplace. Although work-related exposures to materials such as detergents, solvents, plastics, oils, and metallic compounds are often more intense, everyday exposures to jewelry, clothing, hair products, perfumes, creams, and lotions can also result in contact dermatitis.

Causes of Contact Dermatitis

About 80% of cases of OSD are caused by environmental irritants, and the remaining 20% are caused by allergic reactions. It is exceedingly difficult to determine by examination alone which type of reaction a patient has. Complicating diagnosis is the fact that irritating compounds can be allergenic, and allergenic compounds can be irritating. Frequent causes of occupational allergic contact dermatitis include metallic sales, germicides, plants, rubber additives, organic dyes, plastic resins, formaldehyde, and first-aid medications.

Chronic cumulative insult form of irratant contact dermatitis in a health care worker. This job related condition resulted from repeated hand washing with soap and water. Clinically, ill-defined erthema and moderate scaling were present. This form of dermatitis can easily be confused with allergic contact dermatitis or atopic eczema.

Irritant contact dermatitis is caused by direct toxic injury to the skin, triggering a nonspecific inflammatory response. Allergic contact dermatitis is a Type IV delayed hypersensitivity reaction. On initial exposure, an allergen is processed by epidermal Langerhans antigen-presenting cells, which then present the allergen to T helper cells. This results in the formation of specific memory and T effector cells. The process of sensitization takes 5 to 21 days. Re-exposure to the allergen causes the activated T cells to proliferate, which in turn leads to the release of inflammatory mediators. The mediators attract other cells, including cytotoxic T Cells, that induce cutaneous eczematous inflammation at the site of contact, usually within 48-72 hours after re-exposure.

Chronic allergic contact dermatitis in a photographer due to the use of color developers in his home darkroom. Note the scaling and erythema primarily occurred on his fingertips which highlights the area of contact with the sensitizers.

Mathias has outlined seven criteria that are useful for determining whether contact dermatitis is occupationally related. Four of these criteria should be met to judge a patient as probably having OSD:

1. The clinical eruption is consistent with contact dermatitis.
2. The patient is exposed to irritants or allergens at work.
3. The anatomic location of the eruption is consistent with the job-related exposure.
4. The onset and time course of the eruption must be consistent with on
5. OSD.
6. Non-occupational exposures are excluded as possible sources of the dermatitis.
7. The eruption should improve when exposures to the suspected agents are eliminated. This includes exposures outside of the workplace.
8. Patch testing may reveal a likely causative agent

Irritant or Allergen?

Although people vary widely in their susceptibility, irritants will produce a reaction in most individuals when applied in sufficient concentration for an adequate length of time. However, there is no reliable skin test for confirming an irritant reaction. Diagnosis depends on correlating an exposure history to a known irritant with the clinical appearance, distribution, and course of the dermatitis.

Irritant contact dermatitis is divided into two types: acute toxic and chronic cumulative reactions. Acute toxic reactions result from a single exposure to a strong chemical, usually appearing within minutes or hours. The skin usually heals soon after the exposure.

Chronic cumulative reactions are more common and may take weeks, months, or even years to appear. These reactions are often difficult to distinguish from chronic allergic contact dermatitis.

In contrast to irritant-induced disease, allergic contact dermatitis typically affects only a few individuals in a work place. The classic allergic response resembles poison ivy dermatitis, featuring erythema, edema, vesicle formation, and pruritus. Chronic allergic contact dermatitis and irritant reactions may both have erythema, scaling, crusting, excoriations, and lichenification. Mixed allergic and irritant reactions are also possible.

Identifying a non-occupational cause of contact dermatitis can be difficult because patients come in contact with so many materials during daily life. However, the location of the reaction often provides an important clue about the cause. For examples, a rash on an earlobe suggests a reaction to an earring. Dermatitis on the face may indicate that a perfume, cosmetic, or cream is the culprit. A reaction along the hair line points to a haircare product.

Patch Testing

Patch testing is the only reliable method for diagnosing allergic contact dermatitis. The most widely used patch test is the Finn chamber method, which uses a multiwell, aluminum patch. A small of each allergen of each allergen being tested is placed into a well, and the patch is then taped to the upper back of the patient. The patch is removed after 48 hours and an initial reading is recorded. A second reading is made a few days later. The optimal time for the second reading is 96 hours after the patch was first applied.

The Finn chamber method is the most widely used patch test procedure. Small amounts of allergen, usually in a petrolatum vehicle, are placed in the aluminum wells which are affixed to a strip of paper tape. Drops of liquid allergens are placed on filter paper discs that are placed inside the aluminum well. The upper back is the preferred testing site.

Prognosis

In general, people who develop OSD do not have a good prognosis. One study found that 75% of patients with OSD had either persistent or periodic dermatitis, while only 25% had complete clearing. Once dermatitis persists beyond the acute stage and becomes chronic it usually remains despite the best therapeutic efforts. Chronic inflammation tends to produce more permanent changes in the skin that are often difficult to resolve. For this reason, it is critical that acute contact dermatitis receive prompt evaluation and treatment.

Patients with contact dermatitis may also become secondarily sensitized to preservatives that are contained in the topical steroids and moisturizers that physicians use to treat contact dermatitis. Other allergens that may exacerbate a dermatitis include those contained in protective gloves, waterless hand cleansers, first-aid drugs, and barrier creams.

Treatment and Prevention

The key to treatment is removing the allergen and as many irritants as possible from the patient's work and home environment. An effort should be made to replace allergens with similar, nonsensitizing agents Patients are instructed to avoid frequent hand washing with soap and water; mild waterless cleansers may provide an alternative. Gloves are useful to protect the hands, and many types are available. The treatment of choice includes moisturizers and topical steroids. Topical treatments that contain the least sensitizing ingredients should be selected for high-risk patients to avoid a secondary sensitization. Systemic steroids should be reserved for acute, severe reactions, and should never be used for chronic skin eruptions.

Prevention is preferable to treatment for individuals with a history of contact dermatitis. Wet work should be avoided. Protective clothing should be used whenever possible. Selecting the right glove material is also important. A poor choice can actually exacerbate a dermatitis by allowing the allergen or irritant to penetrate the glove and be trapped against the skin.

The following two case histories exemplify the strategies used in diagnosing and managing allergic contact dermatitis:

Case 1:

A 37-year-old woman employed as a phlebotomist presented to National Jewish with a chronic hand rash. She had a history of atopic dermatitis during her childhood. Previous physicians had linked her rash to her history of eczema an current exposure to irritants. The patient had some improvement by decreasing irritant exposure, using topical steroids and moisturizers, and wearing vinyl gloves with cotton liners. However, her rash never completely resolved.

At her initial examination at National Jewish, the patient had bilateral scaly and hyperpigmented plaques involving her central palms. Scaling also existed on her fingers. To decrease her hand washing with soap and water the patient had been using antimicrobial wipes to clean her hands during work. Patch testing revealed that the patient reacted to parachlorometaxylenol (PCMX), the principal preservative in the wipes. A cross-reacting preservative, chlorocresol, was contained in the antiseptic soap that she occasionally used at work. After the patient discontinued her contact with PCMX and clorocresol her hand eczema showed marked improvement.

Case 2:

A 33-year-old man presented to National Jewish with a one-year history of a rash on his hand, arm, and calf. The patient worked as a machinist, and had frequent exposure to industrial oils. Previous physicians had treated the patient with topical steroids and a moisturizing lotion.

Extensive patch testing revealed that the patient was allergic to Quaternium 15, an antimicrobial agent that was added to the oils used at the patient's work places. Quaternium 15 was also the primary preservative in the moisturizing lotion that the patient had been using.

Because Quaternium 15 is a formaldehyde-releasing preservative, we instructed the patient to avoid other formaldehyde-releasing compounds, such as Bronopol and Diazolidinyl urea. The patient's employer began using an alternative additive, and we switched the patient's moisturizing lotion. His rashes subsequently cleared.

References

1. Mathias CGT. Contact dermatitis and worker's compensation: criteria for establishing occupational causation and aggravation. J Am Acad Dermatol 1989;20:842-48.

Additional Reading

1. Stewart LA. Occupational contact dermatitis. Immunol Aller Clin North Amer 1992;12:8l3-46.

2. Hogan DJ, Dannaker CJ, Malbach HI. Contact dermatitis: prognosis, risk factors, and rehabilitation. Semin Dermatol 1990;9:233-46.

Faculty

The Medical Scientific Update, a publication of the Office of Professional Education at National Jewish, provides information to physicians about our clinical and research programs in allergic, respiratory, and immune system disorders. The Web edition of the Medical Scientific Update published by the Gerald Tucker Memorial Medical Library.