"It's your skin, it's what you keep your body in," goes the Garrison Keillor song, and Marc Lappe would approve the wholesome nurse from Lake Wobegon and her sage advice about paying attention to this organ. This small book offers an introduction to the skin, including a survey of cultural attitudes and customs that have grown up around it, and goes on to discuss primarily medical issues, such as the functions of the skin and common -- and not so common -- diseases. Lappe also leaves the reader in no doubt as to the single kindest thing a person can do for his skin, and it's not the Lake Wobegon nurse's advice to "drink eight glasses of water a day -- to wash away impurities!" Marc Lappe wants his readers to abhor the sun.

The sun figures prominently in this book as a potent threat to skin function that has proved at least a partial motivation for the evolution of variations in pigmentation. Lappe, a Ph.D. pathologist, has studied skin for some thirty years, and he underlines some now-obvious points about exposure of skin to light (and chemicals) that bob just beneath the surface of the practice of medicine. A key aspect of his argument is the skin's mechanism for "immune surveillance," a phenomenon that has been demonstrated over the past few decades. Not just a passive covering for the body, the skin has several layers and many specialized cells, including a rudimentary immune system.

So why is sun exposure so dangerous? Why doesn't that immune system repair damage as the sun causes it? With limited sun exposure, it can. But heavy sun exposure, ultraviolet (UV) light exposure in particular, is especially damaging to the very cells that engage in immune surveillance. This is something that doctors understand well enough that they have regularly used light "therapy" to knock down the immune system in order to alleviate the symptoms of individuals with autoimmune disorders. Immune suppression is also the way that steroids work to reduce inflammation.

Lappe is a toxicologist, and he headed the Hazard Evaluation System when it was initiated by the California Department of Health in 1979. He has continued to take a strong interest in the political dimensions of the medical ecology of the skin and is particularly concerned about cosmetic issues. As sympathetic as he is to the human cultural developments of skin ornamentation (our counterpart to the peacock's tailfeathers), he is strongly opposed to attempts to manipulate the skin that result in any sort of hindrance to skin or body function -- two examples he discusses are the teratology of isotretinoin, a treatment for acne, and the autoimmune phenomena that clearly result, in his opinion, from injection or leakage of silicone fluids. (He notes that two recently published studies fail to support that link. He fails to mention, however, that over the past few years he has been an expert witness in breast implant cases.)

Although the index is incomplete, this thoughtful and informative book is heavily referenced, which is useful, since it brings up many questions. Readers may especially wish to follow up some of the cultural discussions, which are interesting but controversial, as is his seductively simple confidence about the silicone issue. They are, however, not the centerpiece of the book; The Body's Edge: Our Cultural Obsession with Skin is first and foremost an affectionate and respectful tour of the largest organ of the human body in all its myriad splendors. At the same time, Lappe strongly states his concerns about the way culture and industrialization have threatened human health with expectations like "tan is healthy," damage to the ozone layer, and the exposure of humans to toxic chemicals. By making us aware of the strength -- and vulnerability -- of our most visible parts, he urges all of us to save our skins.

Next week, the Net Net reviews Science on Trial: the Clash of Medical Evidence and the Law in the Breast Implant Case, by New England Journal of Medicine executive editor Marcia Angell, M.D.