The skin is the largest single organ.  It covers 20 square feet of surface.  The skin's purpose is to protect the body from outside substances, chemicals and bacteria.  The skin has two layers, together both are less than 1/8-inch thich.  The epidermis (outer layer) is only 1/250th of an inch thick.  The dermis is only 1/50th to 3/25ths of an inch thick.

Worksite materials can cause skin problems. Some materials 'insult' and injure skin. Some pass through it into the bloodstream.  Examples of these materials are:

Solvents can remove the fat from skin, drying it and making it more susceptible to cuts and the effects of other chemicals. Solvents may also pass through the skin to enter the blodstream.

Primary irritants such as acids and bases, cause direct damage to the skin, and may result in rapid burning and reddening. Irritants may be found in cualks, sealant and ther trade materials.

Sensitizers in workplace materials may cause an allergic response. The reaction may be local or widespread. Sensitization is an immune response. The immune system fights a foreign substance. Usually, the material causes no change on first contact. Once a person is sensitized, small amounts can trigger a strong reaction. Many people cannot tolerate further exposure.

Possible sensitizers used by sheetmetal workers include: isocyanates, epoxies,hexavalent chromium (Cr6+ ), and additives in rubber gloves.

Worksite cleaners too often are caustic and abrasive. They also may contain sensitizers like lanolin, limonene, or perfume and irritants like alcohol.

Worksite conditions can determine whether a worksite material will cause skin problems.

• How long does the material contact the skin?
• How often does a worker use the material?
• Is there mechanical trauma or abrasion of the skin (a break in the barrier)?
• Is the material trapped or occluded to the skin with gloves, creams, lotions, petroleum jelly, or barrier creams?
• Are there adequate hygiene facilities?

Environmental factors can cause skin problems directly or they can work with other factors to increase skin problems:

• Heat causes sweating. Sweat dissolves chemicals and brings them into closer contact with the skin. Heat increases blood flow at the skin surface and increases absorption of materials into and through the skin.
• Cold dries the skin and causes microscopic cracks. Cold changes blood flow at the skin surface and leads to loss of feeling.
• Humidity increases sweating. High humidity keeps sweat from evaporating. Extremely low humidity can dry skin as sweat evaporates.
• Sun burns and damages skin. Sun can increase absorption of chemicals. Sun reacts with some chemicals to cause photosensitization.

Individual factors can affect work-related skin problems. These include:

• pre-existing dermatitis
• genetic predisposition
• knowledge
• attitude
• personal behavior/workpractices

There are no studies that tell us how many sheet metal workers have allergic dermatitis, or how many will develop it in any given year (incidence), in the United States. We do have some information from workers compensation claims, but the true rate of dermatitis is certainly higher that the number of dermatitis claims to workers compensation, for research has shown that most occupational diseases are under-reported. In Oregon between 1990 and 1997 the claim rate to workers compensation was 7/100,000 construction workers, and a study from Germany found a similar incidence.  Among construction workers with skin problems 65% of the dermatitis was caused by work, with 40% being allergic to chromium, 10% to nickel, and 7.5% to epoxy resins in one study.