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Q: Should I request the CA-125 test for ovarian cancer at my next checkup?

A: It’s recommended only for women who have symptoms or a strong family history of ovarian cancer—not for general screening. The test, which measures a protein marker in the blood, often misses women with ovarian cancer (false-negative results) or makes women think they have cancer when they don’t (false-positives).

If used by itself, CA-125 is not good at detecting early ovarian cancer. In fact, the test identifies only about half of women with early-stage disease, because the protein may not yet be elevated. It’s better at catching cancer at later stages.

On the other hand, CA-125 can be elevated for reasons other than ovarian cancer. This is especially true for premenopausal women and can lead to needless anxiety, further testing, and even surgery. Factors that affect CA-125 include menopausal status, ovarian cysts, pelvic inflammatory disease, fibroids, endometriosis, pregnancy, colitis, and other cancers. In fact, the great majority of women who test positive do not have ovarian cancer.

If the test is indicated, it should be done in conjunction with transvaginal sonography and a pelvic exam. Many experts advise that it be repeated over a period of time (serial testing) to see if CA-125 is rising and at what rate. This is thought to provide more accurate information than a single test.

As yet, there is no general screening test for ovarian cancer. Tests with better sensitivity are currently under investigation.

Q. Is oil of lemon eucalyptus a good mosquito repellent?

A: Fairly good. The Centers for Disease Control and Prevention recently said it is as effective as low concentrations of DEET, which remains the gold standard. In 2002 a University of Florida study found it was effective for two hours, similar to 7% DEET (24% DEET worked for five hours). In 2004 a USDA study found it was as effective as 15% DEET. For ordinary purposes, such as backyard activities, 10 to 30% DEET is adequate for adults.

Several repellents now contain oil of lemon eucalyptus, including Repel and Off Botanicals. But keep in mind:

• If you’re going to the tropics or other heavily infested areas, oil of lemon eucalyptus may not be good enough. It has not been tested against mosquitoes that spread malaria and some other diseases. Instead, use higher concentrations of DEET (up to 50%) or controlled-release formulations. The CDC has also recommended repellents containing picaridin, as we said in our July issue, as an alternative to DEET.

• Many other plant oils, such as citronella, soybean, and peppermint, are promoted as repellents, but are much less effective.

• As the labels warn, don’t use products containing oil of lemon eucalyptus on children under three, since it has not been studied in them.

• Don’t put pure eucalyptus oil on skin.

Q: What causes dark circles under my eyes, and is there anything I can do to get rid of them?

A: Dark circles are usually a result of genetics and aging. The thin skin below the eyes becomes thinner over time, revealing the underlying blood vessels, especially if your skin is extra-transparent or if you have excessive veins. The fat above the cheek bone also thins with age, creating a hollowed effect, which adds to the appearance of dark circles, while fat pads just below the lower eyelids can develop with age and cast shadows. Sun exposure (which increases pigmentation), nasal allergies, estrogen use, certain medications, and possibly fatigue may also contribute to dark circles.

If the circles really bother you, consult a dermatologist who can determine their cause and possible treatment. Options include topical gels, bleaching agents, chemical peels, laser treatments, or injections of fillers. But results may be disappointing, and no treatment is risk-free. Some products may cause over-lightening and pigment irregularities. As a last resort, a plastic surgeon can perform a lower-lid blepharoplasty ("eye lift") to remove fat tissue.

Over-the-counter cosmetic products may contain some of the same ingredients used in doctors’ offices, though in lower concentration. They may also contain a kitchen sink of others, such as papaya, chamomile, sweet hazel, resveratrol, and seaweed extract. Some ingredients, such as hydroquinone and DMAE, are promising, but there’s little or no supporting data for most. It’s hard to know which products are best for you unless you’ve consulted a dermatologist; adverse reactions are possible. And the products are expensive.

A temporary quick-fix is to use an under-eye concealer (yellow tones neutralize the blue of blood vessels). Be sure also to treat allergies if you have them, and wear sunscreen and large sunglasses.

Q: Your article in May about reusing disposable plastic water bottles didn’t mention the more durable plastic bottles I use for hiking. Is it true that these bottles leach a harmful chemical?

A: Water bottles that you refill, such as the popular Nalgene brand, are often made from polycarbonate plastic (identified on the bottom by the number 7). So too are some baby bottles, water cooler bottles, food-storage containers, and the linings of most food and beverage cans.
This plastic, which is clear, lightweight, hard, and virtually indestructible, contains Bisphenol A (BPA), a so-called "endocrine disruptor" that’s been linked in animal studies to hormonal and reproductive problems, neurological changes, altered immune function, and other abnormalities. High doses in rats and mice, however, have not been shown to cause cancer. No human health risk has been established, but there have been concerns because traces of BPA have been detected in human urine samples.

Under normal conditions, only minute amounts of residual BPA are likely to leach from polycarbonate bottles. The Food and Drug Administration and other regulatory agencies, including the European Union’s Scientific Committee on Food, consider the plastic safe for repeated use.

If you are concerned about exposure, wash polycarbonate bottles with mild detergents and warm water—not in the dishwasher—and rinse well. Keep them out of the heat, and discard if they start to discolor or develop spider cracks.

UC Berkeley Wellness Letter, August 2005