My patient has a hand dermatitis that appeared to begin at his job. Does this mean he has an occupationally related skin disease?

Not necessarily. Just because a patient has a rash, and he or she works, does not mean it is job-related. To help make that determination, investigators have outlined seven criteria to be assessed. Four out of the seven should be present for reasonable medical probability:

1. Is the eruption consistent with a contact dermatitis? It should look like an eczematous dermatitis and not like other disorders (i.e., vasculitis).
2. Are there occupational exposures to possible irritants or allergens? There should be known documented irritating or sensitizing compounds to which the patient has been exposed at work.
3. Is the anatomic location of the eruption consistent with the exposure a worker would obtain on the job? For example, a worker may handle a chemical daily and break out with dermatitis only on his back. This is not consistent with an OSD because he should have developed an eruption where he contacted the compound the most, namely, his hands.
4. Is the onset and time course of the eruption consistent with contact dermatitis? Allergic contact dermatitis is a delayed reaction (occurring 48 to 72 hours after exposure), while irritant reactions may be immediate or delayed. Contact dermatitis is not, for example, consistent with a worker’s one-time exposure to a chemical when a rash occurs 3 months after that one incident.
5. Are nonoccupational exposures excluded as a possible cause of the dermatitis? Hobbies, second jobs, and household contactants should be pursued as possible sources of contact dermatitis.
6. Does the eruption improve away from work? Work-related eruptions tend to improve when a worker is away from his job, although sometimes the same allergens and irritants may be found at home. Also, approximately 25% of workers with an OSD have a chronic and persistent dermatitis despite leaving their job and therapeutic intervention, and improvement does not occur when the worker is away from his place of employment.
7. Does patch testing reveal a likely causative agent? If a positive patch test reveals a likely allergen source with which the worker had contact, it is useful for pointing to the job exposure as the problem. However, patch tests must be interpreted within the context of the patient’s history and physical examination. A positive test does not necessarily mean the allergen is responsible for the patient’s current dermatitis, because it could be unrelated sensitization. The patch test reaction must always be assessed for its relevance to the present eruption.

Mathias CGT: Contact dermatitis and workers’ compensation: criteria for establishing occupational causation and aggravation, J Am Acad Dermatol 20:842–848, 1989.