julia roberts

Photo: Laspata Decaro, from the book Metamorphosis

Your ponytail is shrinking...or your part's getting wider...or there's more hair in the shower drain. Take heart—you're not alone. According to New York City dermatologist Neil Sadick, MD, up to 80 percent of women will have some hair thinning in their lifetime, even if only temporarily. It's normal to shed 50 to 100 hairs a day, says NYC dermatologist Doris Day, MD. If you're losing more than that, a doctor's visit is in order. Here are some common causes and treatments.

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Cause: Genetics (the most likely culprit)

Treatment: Minoxidil, the only topical ingredient that's FDA approved to regrow hair in women. Rogaine has just launched a 5 percent minoxidil foam for women ($30; drugstores). (Previously, the only option for women was 2 percent.) Sadick also suggests in-office red-light laser treatments, which can increase the number of hairs as well as the diameter of the hair shaft.
birth control

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Cause: Hormonal changes

Treatment: Switch birth control pills. Or if you're past childbearing age, your doctor may suggest a prescription antiandrogen medication, like spironolactone (brand name Aldactone) or finasteride (brand names Propecia and Proscar) off-label, says NYC dermatologist Fredric Brandt, MD.
losing hair

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Cause: Inflammation

Treatment: A prescription topical steroid or a zinc shampoo, in addition to the treatments listed on slides 2 and 3.
vitamin d

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Cause: Low iron or vitamin D levels

Treatment Adjust your diet or add supplements. First talk to your doctor, who can then prescribe a supplementation program tailored to your level of deficiency.

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Cause: Medication

Treatment: Switch meds if possible.
thicker hair

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Quick Fixes
Long-term measures can take three to six months to yield results. In the meantime, it's worth trying some temporary solutions. Hair fiber powders (they come in a variety of shades) can be shaken on sparse areas to mask them. Try Keranique ($40; Keranique.com), Toppik ($25; Toppik.com), or Viviscal ($25; Viviscal.com). You can also make individual hair shafts thicker by using the leave-in treatments Redken Cerafill Maximize Dense Fx ($45; Redken.com for salons) or Nioxin DiaMax Advanced ($50; nioxin.com for salons).

The Spray You Should Try
Serge Normant Dream Big Instant Volumizing Spray ($25; SergeNormant.com)

Add some oomph to limp hair with this lightweight aerosol spray, which has plumping polymers that increase volume without weighing down your style. Apply to the roots to create lift or all over for a midday refresher.