Module 4: Occupational Skin Disease -

HAZARDS TO THE SKIN:

Most skin diseases can be caused by work and thus considered occupational. One needs to be aware that any skin condition may be due to occupational exposure although some diseases are more common than others.

Insults to the skin are many and varied. The skin is subject to mechanical, physical, biological and chemical hazards and one has also to account for the effects on pre-existing skin diseases.

Mechanical hazards:

These include trauma, friction, pressure, vibration, pounding, abrasion and penetration injuries.

Mechanical hazards cause irritant effects, or result in adaptive protective responses. The irritant effects are either acute or chronic.

Acute changes include urticaria, blisters, erosions, necrosis, burns or ulceration of the skin. Chronic mechanical insults lead to conditions such as the vibration syndrome and deformities.

Chronic adaptive processes include thickening and hyperkeratoses of the skin in response to these repeated stresses. Classic examples of this adaptive response are corns and calluses due to repeated pressure and lichenification of the skin due to chronic scratching.

Physical hazards:

Physical hazards include temperature, radiation, electricity, humidity, airflow and occlusion. The physical hazards cause mostly irritant effects but they must also be recognised as hazard modifiers.

Acute effects or damage include burns, miliaria from occlusion and heat, acne, urticaria and eczema. Eczema is precipitated by dry environments causing dry skin eczema. Chronic effects include cancers such as skin cancers following radiation damage, occlusion acne and eczema.

Biological hazards:

There are a wide range of biological hazards that interact with the skin. These range from viruses through bacteria, fungi, and parasites to insects, animals and plants. All of these are potential biological hazards. Biologic hazards have either a direct effect on the skin or they act as vectors.

Direct effects include infections or infestations of the skin or bites and stings.

The vector effects are via the introduction of infectious agents or substances causing allergies following bites or stings. Vector effect can also occur via association where by-products left in the environment act as allergens or sources of infection. An example of this would be histoplasmosis associated with rat droppings.

Chemical hazards:

Chemical hazards include any organic or inorganic compound whether in solid, liquid or gaseous form. Chemical hazards can have either a direct effect causing irritation or toxic effects or they can act as allergens.

Examples of the irritant or toxic effects include burns, necrosis, ulceration, pigmentory changes, thickening and hyperkeratoses of the skin and eczema. Chronic repeated exposure can result in "skin hardening" (thickening and hyperkeratoses) a protective adaptive response. Systemic toxicity can occur via product absorption through the skin.

The clinical manifestations of chemical allergens include urticaria, eczema and lichen planus. Systemic effects include anaphylaxis, urticaria, or systemic disease.

Pre-existing skin conditions:

Pre-existing skin conditions offer a real challenge for occupational skin disease assessment and management. Pre-existing conditions such as atopic eczema, fair skin or psoriasis are in themselves potential hazards or hazard modifiers.

Workers with a damaged skin barrier are more predisposed to contact dermatitis than those with normal barrier function. Patients with atopic eczema thus have increased susceptibility to irritant and allergic dermatitis. Fair skinned people working in an outdoor environment are more susceptible to the long-term effects of chronic radiation and skin cancer development than people with darker skins are. Patients with psoriasis may develop chronic plaques over areas of trauma such as the palms and soles. It may also be precipitated as an isomorphic phenomenon in susceptible workers by contact dermatitis giving rise to persistent psoriasis. Although atopic eczema and psoriasis are not caused by the work environment, they are aggravated by it and therefore are work aggravated conditions.