Evaluating dermatitis studies

Does the range of factors affecting dermatitis limit the value of evidence-based studies?

In an August 2010 Occupational Health magazine article on the British Occupational Health Research Foundation (BOHRF) study on dermatitis, the BOHRF study used the SIGN (Scottish Intercollegiate Guideline Network) guidelines to evaluate studies.

Having been involved in an evidence-based study using SIGN, my view is that, while this does ensure that the studies meet very high standards, it runs a risk of excluding much data, both scientific and experiential, that can add valuable information to any recommendations.

For example, there is a statement in the article that: “A temporal relationship between symptoms and work indicates that a person’s job has either contributed to or caused their occupational contact dermatitis or urticaria.” This is not necessarily the case, for two reasons.

Exposure to irritants

First, with irritant contact dermatitis, this is almost never the result of skin contact with a single chemical, but arises out of repeated contact with many different irritant substances, both at home and at work. Since we tend to spend about eight hours each day at work and 16 away from the workplace, and since we encounter many different irritant chemicals away from the workplace, it is too simplistic to assume that an irritant contact dermatitis is due to workplace exposure.

I have investigated several cases of suspected occupational contact dermatitis where the investigation revealed that the major cause was non-occupational exposure, even though it appeared to be temporally aligned to time spent at work.

An example is the case of a worker who developed hand dermatitis while working with nickel-plated components. A patch test showed that she was allergic to nickel. The dermatitis cleared when she went on holiday and returned within a few days of her returning to work. The assumption, therefore, was that the dermatitis was due to her exposure to nickel at work.

I was asked to advise on what action should be taken to ensure that other workers did not develop the same problem. Investigation revealed that the components she was handling did not release nickel, so this could not be causing her dermatitis. Further investigation revealed that in her spare time she worked as a hair stylist. Her dermatitis was an irritant contact dermatitis due to contact with shampoos, etc.

Interrelated skin problems

Second, the article appears to suggest that irritant and allergic contact dermatitis can be considered as separate, discrete skin problems. This is not necessarily the case. It is not uncommon to find that a hand dermatitis has both irritant and allergic components. We have no real way of distinguishing to what extent each plays a role in the skin problem. Add to this other factors and the picture can become complex. I have seen several cases where purely psychosomatic reactions have resulted in what was assumed to be an occupational contact dermatitis, and in one case an anaphylaxis.

None was occupational in origin.

Additionally, the BOHRF study considers only actual skin disease. There is abundant evidence that contact between skin and chemical can result in uptake and systemic damage, often with no visual or sensory indication that this is happening. Therefore, concentrating purely on skin effects when carrying out a risk assessment could lead to someone ignoring other, more significant, risks.

In conclusion, while the BOHRF study is accurate and objective, in my considered opinion it has limitations in scope and does not provide a definitive guide to the prevention of damage to health due to workplace skin exposure.

Chris Packham is a partner at EnviroDerm Services. Tel: 01386 832 311/831 777.

Response from author of the article on the BOHRF guidelines Diane Romano-Woodward

I agree that evidence-based studies “run the risk of excluding much data, both scientific and experiential, that can add valuable information to recommendations”.

I was part of the evidence review and I must say that we found a great many of the papers lacking in substance, and the information contained therein could not be used. However, there were some gems that had to be excluded because they were “expert opinion”. I am thinking particularly of one paper that dealt with the different manifestation of occupational skin disease in skins of colour.

My remit was to write an article about the BOHRF guidance, which made the possibility of adding experiential advice impossible. Perhaps there is a place for another article that is more practically and experientially based. I will contribute the first piece of advice: when you are looking at hands that are affected, have a look at the feet as well.


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