If you see dark lines on the nail beds
Texas-sized moles aren't the only red flags for skin cancer--the disease can also develop under your nails. Yellowish, brown, or black stripes are a sign of cell damage, possibly from melanoma, the deadliest form of skin cancer, says Ariel Ostad, M.D., a dermatologist in New York City. With early detection and treatment, though, about 95 percent of cases are curable, so have your dermatologist take a second look.
If you see bright white stripes
Everyone gets white spots on their nails from time to time (usually it's a sign that you banged your finger in a drawer), but if you see long horizontal bands of discoloration on the nail's surface and you've been feeling fatigued lately, it could be bad news for your kidneys. "These bands can be a signal that the kidneys aren't able to filter out protein from your urine," Ostad says. That means your body is losing protein faster than you can shovel in filet mignon--and that can lead to kidney failure. Visit your doctor ASAP for a urine test.
If you see a patch of rough, dark skin
Unless you've been going overboard with the self-tanner, you could have diabetes, says Michael Smith, M.D., WebMD's chief medical editor. Excess insulin in your bloodstream can cause skin cells to multiply abnormally fast, leading to a buildup of tissue and melanin. This makes the skin look darker and feel thicker. "It most commonly occurs in the armpits, neck, or groin," Smith says. A simple blood test can determine whether you have the disease, which affects about 24 million Americans--nearly a quarter of whom are undiagnosed.
Your Eyelids, Knees, And Elbows
If you see small, soft lumps that look white or waxy
The good news: It's not a zit. The bad news: These are small deposits of cholesterol, Smith says. Unfortunately, "by the time they appear, your cholesterol levels are probably sky high; this is a serious risk factor for heart disease." Yet reducing your numbers by just 10 percent slashes that risk by as much as a third. See your doctor for a cholesterol check, and ask her about lifestyle changes or prescription drugs that can get your levels down.
More from Women's Health:
If you see thinning hair
Could you fashion one of Britney's weaves out of the hair clogging your drain? Excessive hair loss is a common indicator of a thyroid disorder, which affects about 10 percent of American women. When your thyroid (a gland in the middle of your neck) is out of whack, it can disrupt the balance of male and female sex hormones. The result: More strands in your brush and hair that feels coarse and brittle, says Sandra Fryhofer, M.D., a physician in private practice in Atlanta. Your doc can measure the amount of thyroid-stimulating hormone in your blood--if you have too much or too little, you'll need medication to regulate it.
If you see your scalp shedding like a snake