The truth in beauty.

Not for nothing did our ancestors worship the sun, the source of Earth's fertility and associated revels. What the ancients didn't understand, however, was the link between sun exposure and skin cancer. Whether you celebrate the season on a mountaintop or basking by the swimming hole, it pays to protect your skin. The key: read ingredient lists, and don't be caught napping at the expense of your or your children's health.

Sunscreens and Sunblocks. The skin is an absorptive organ, so it makes sense to use the least toxic products on it. Unfortunately, most sunscreens contain at least some iffy chemicals, including benzophenone, homosalate, and octymethoxycinnamate, shown in animal tests to disrupt hormones and affect development of the brain and reproductive organs. PABA (para-aminobenzoic acid) has caused allergic reactions, and padimate-O and parsol 1789 (avobenzone) have the potential to damage DNA. At the very least, these chemicals can irritate skin; they can also affect the health of aquatic ecosystems long after washing off.

A healthier choice is blocks that create a barrier against damaging UVA and UVB rays. These include zinc oxide and titanium dioxide, which are "much less likely than [chemical] sunscreens to penetrate human skin," according to biochemist John Knowland of Oxford University. Avoid all of these products on children under six months; instead, keep babies out of direct sun and use protective clothing and hats.

Chapsticks and Skin Creams. Dry skin and lips can tempt us to slather on moisturizers and balms. Are these safe? Not always. In September 2004, the European Union passed a rule banning hundreds of known or probable carcinogens, mutagens, or reproductive toxicants from cosmetics. Yet in the United States, neither cosmetic products nor their ingredients are reviewed or approved by the Food and Drug Administration before being sold.

Until ingredient bans are adopted worldwide, it's best to read labels. Many creams and chapsticks are based on petroleum, a nonrenewable resource; this includes petrolatum, a.k.a. petroleum jelly, which can cause allergic skin reactions and, if ingested excessively, diarrhea. Other problematic ingredients are glycol ethers, such as the common skin irritant propylene glycol, some of which have been linked in lab tests to birth defects and reproductive-system harm. The preservatives methyl-, butyl-, ethyl- and propyl-parabens are skin irritants that have also shown up in breast tumors. And formaldehyde, a probable human carcinogen, is found in such preservatives as bronopol, diazonlidinyl urea, DMDM hydantion, imidazolidinyl urea, and quaternium 15.

Don't be lulled by a product's "fragrance," a catchall term that can conceal the presence of phthalates, plasticizing chemicals that have been linked to cancer and hormone disruption in animals. Following demands by the Breast Cancer Fund and other activists, Revlon, L'Oreal, and Unilever agreed to stop using dibutyl phthalate in their products. Fragrance-free creams are the least allergy-provoking, but if you prefer scents choose items containing plant essential oils such as lavender or rose.

Because babies are rapidly developing and have sensitive skin, they are most vulnerable to irritating ingredients. Happily, there are now many diaper creams based on natural inputs, including Weleda, Terressentials, Martina Gebhardt Naturkosmetik, and Burt's Bees.

Insect Repellents. Mosquito-borne diseases such as malaria and West Nile virus are spreading on the wings of climate change. But eye that label before using a conventional repellent. Most contain DEET (N, N-diethyl-m-toluamide), which should never be used on children under two or applied directly to the face, hands, or damaged skin. DEET can cause blisters, rashes, and eye irritation as well as lethargy, disorientation, and mood swings; in some cases, overapplication has resulted in death. The compound can enter waterways and is listed by the U.S. Environmental Protection Agency as "slightly toxic" to birds, fish, and aquatic invertebrates.

A better alternative is to wear protective clothing, avoid tick-prone areas, and stay indoors when mosquitoes are out. Soybean oil and some botanical oils, such as citronella, lemongrass, peppermint, and cedarwood, also repel bugs somewhat. Use the strong stuff (no more than 10 percent DEET) only as a last resort, applying it to clothing and hats, not skin.

See www.thegreenguide.com for product reports on moisturizer, shampoo, makeup, sunscreen, deodorant, and insect repellent as well as for the "Dirty Dozen Ingredients" in Green Guide #100.

Visit the Worldwatch online consumption portal at www.worldwatch.org/ww/consumption/

by Mindy Pennybacker, with reporting by Molly Rauch and Claire Gutierrez

Mindy Pennybacker is editor of The Green Guide, published by The Green Guide Institute (www.thegreenguide.com), which provides the research for this department.