From the stratum corneum to the hypodermis, an engrossing, warts-and-all census of the body's largest organ. Making up nearly 15 percent of our body mass, the skin protects us, defines us; it even reflects our internal state of health. For as LappÇ (Chemical Deception, 1991, etc.), the director of the Center for Ethics and Toxic Substances (Gualala, Calif.), notes, it is the ``border between wellness and dysfunction.'' Surprisingly enough, for something so visible and apparently simple, much about the skin remains unknown. It may have its own primitive version of an immune system. The colonies of fungi and bacteria that swarm over its surface may perform important symbiotic functions for the host. Humans are one of the few animals without significant body hair, but the evolutionary reasons for this are not understood. LappÇ's own theory is that it was a way to free humans from the onerous, time-consuming chore of grooming themselves in search of lice, mites, etc. Of course, given that Americans spend six to ten percent of their disposable income on cosmetic products (many of which are completely ineffectual), the actual time saved may be minimal. Certainly, without skin, complex life forms could not have evolved. Unfortunately, complex life forms have a bad record of looking after their skin. In the Middle Ages, arsenic was popularly used as a rouge, while lead powder was employed as a whitener. More recently, despite clear experimental findings of its potential hazards, according to LappÇ, silicone was widely used in cosmetic surgery. LappÇ also bluntly chronicles the many dangers of sun exposure (current suntan lotions may not block certain hazardous rays), which we ignore at our peril as the ozone layer thins. LappÇ's account is not as well organized and structured as it should be, and he occasionally lapses into convoluted science- speak. But he has succeeded in taking a subject that usually receives only skin-deep attention and making it both engaging and provocative.