While some people may view skin conditions as nothing more than annoyances or trivial problems, for many others they are causes of significant distress and may even compromise their life-styles. Many complaints of itching or rashing are related to allergenic substances that are applied to or come in contact with the skin either at home or in the workplace. Regarding the latter, the National Institute for Occupational Safety and Health (NIOSH) maintains that widespread, debilitating work-related skin disorders are the most pervasive current occupational health problem in the United States, accounting for more than one-third of all work-related health problems. Since occurrences in the home go unreported, one can only speculate on the extent of the problem there, but it is likely to be quite widespread and significantly distressing as well.
Contact Dermatitis
Before discussing the subject of allergic contact skin allergy, or allergic contact dermatitis, as dermatologists call it, you need to understand the essential difference between an irritant contact dermatitis and an allergic contact dermatitis. Occasionally the signs and symptoms of each are so similar that even your doctor may find it difficult to distinguish between the two.
Irritant Contact Dermatitis
Not every skin rash stemming from contact with a certain chemical substance is an allergy. In fact, the vast majority of reactions, about 90 percent, that result from direct skin contact are nonimmunologic or irritant reactions and for that reason merit inclusion in any discussion of contact-induced skin eruptions. Strictly defined, irritant contact dermatitis is any form of toxic skin reaction due to direct skin contact with either harsh or caustic chemicals or other environmental agents found in the home or workplace. But unlike allergic reactions, in which only predisposed ("previously sensitized") individuals are at risk, irritant reactions, particularly those caused by strong irritants, can happen to anyone who is exposed to the irritating substance. In other words, direct contact with concentrated sulfuric acid would be expected to irritate or burn anyone's hands severely, not just some people's.
Common irritants include paints and solvents (such as alcohol, acetone, turpentine, and carbon tetrachloride); surfactants (soaps, detergents, and emulsifying agents); drying agents (astringents, toners, clarifying lotions, and others); abrasives (such as particle-containing soaps and facial masks); acids (such as battery acid and acid-containing cosmetics), alkalis (such as household lye and drain cleaners); wood preservatives; cement; lime; oils and tars; enzymes (either naturally occurring or synthetic chemicals used to speed up chemical or metabolic reactions); and certain hypertonic (highly concentrated) solutions. Even plastics and some metals may cause irritant contact dermatitis.
As a group, soaps which function to permit normally water-repellent grease and grime to be rinsed away by plain water are one of the most common kinds of irritants because they also compromise the skin's barrier function by removing the natural oils necessary for maintaining the integrity of the upper layers. Repetitive use (especially of pure alkaline soaps or abrasive cleansers) opens the way to abnormal skin water loss and chapping. In addition, traces of soap residue that are often left on the skin after washing can themselves further irritate the skin, especially when coupled with wetness or perspiration. Many people are affected in this way.
When it comes to irritant reactions to weaker agents than soaps, there seem to be individual differences in tolerance to irritation. This is possibly due to inherited variations in the thinness of the upper layers of the skin or to differences in amounts of natural surface oils. As a rule, thick-skinned and oily-skinned persons tend to be more resistant to irritation.
The specific site of exposure as well as environmental factors also play a role in this condition. For example, the thin, more permeable skin of the eyelid, the face, and the genitals are far more likely to react to irritants than the thicker skin of the extremities, trunk, or buttocks. In general, high humidity tends to increase the possibility of irritation because moisture enhances the penetration of irritants. And at the other extreme, very low humidity, by drying and chapping the skin, can also promote irritant reactions.
Despite the existence of myths to the contrary, there seem to be no clear-cut racial, sexual, or age barriers as to who is most likely to suffer irritant reactions. For example, medical science has debunked the common myth that white skin is more prone to irritation than black skin. In fact, current research suggests that the reverse may even be true. Similarly, investigations have questioned the notion that women are more susceptible than men. While such reactions are indeed more common in women, many believe this reflects their greater overall exposure to potential irritants (by way of cosmetics and household cleaning products) than it does to any inherent gender predisposition. Finally, while factors such as thinner skin and decreased natural oil gland secretion would lead one to predict that elderly skin is more easily irritated than younger skin, this also is not necessarily the case. When it comes to resistance or susceptibility to irritant reactions, mature skin seems to fare about as well as younger skin.
