Do you find yourself scratching your scalp on the regular? If the breeding ground for your hair isn't in the best shape, your follicles have no chance of thriving. "An unhealthy scalp often leads to inflammation, which makes it difficult for hair to grow," says Marotta. Skin conditions that cause itchy, flaky and red scalps, such as seborrheic dermatitis (better known as dandruff), psoriasis, sunburn and fungal infections can all contribute to hair loss in this way.

Solve It:
If you suffer from dandruff, pick up a dandruff shampoo, but if the itching and redness get serious, head to a dermatologist or trichologist for a more potent solution. In the meantime, celeb stylist Diane C. Bailey recommends regular scalp massages to increase blood flow to the scalp. "This helps nutrients travel to follicle sites where hair cells are reproduced." Bailey recommends choosing a hair oil that contains tea tree, (like Wen Tea Tree Oil, $20) baobab, peppermint, rosemary, or ylang-ylang oils, all of which stimulate and soothe the scalp. Massage all over your scalp with the pads of your fingers for three minutes, then shampoo out.

After menopause, about 40 percent of women experience hair thinning, which is almost the same rate of hair loss in men. Women, however, tend to thin out all over, rather than develop the signature male pattern baldness. Fluctuations in hormone levels are definitely to blame, though many of the other hair loss causes we've discussed (genetic predisposition, unusual levels of stress, vitamin deficiencies) also make a more notable appearance at this point in a woman's life.

Solve It:
According to hair loss specialist Dr. Alan Bauman, this type of hair loss can't be cured with hormone replacement alone. "Most women benefit from a combination of pharmaceutical and lifestyle changes, but results are always proportional to the patient's level of discipline." Bauman suggests treatments and ingredients "that protect and enhance hair follicles," such as compounded topical minoxidil, found in Keranique, $30, a hair regrowth treatment designed specifically for women, Formula 82M, platelet-rich plasma injections, Bimatoprost (the active ingredient in Latisse), low-level laser therapy. He's also a fan of nutritional supplements like Viviscal, $49.99, and pharmaceutical grade biotin.

Autoimmune diseases, in which the body has an inappropriate immune response against things normally present in the body, are also responsible for hair loss in women. Lupus, for example, affects about 1.5 million people, and tends to strike women during their childbearing years. "The degree of hair loss can range anywhere from losing clumps while shampooing or brushing, to bald patches and a rash on the scalp." Alopecia areata is another autoimmune disorder in which the immune system specifically attacks hair follicles. "It affects about 4.7 million people in the United States, and occurs equally in men and women," says Marotta.

Solve It:
If you start to notice balding patches (usually circular or oval in shape), and tingling or pain on the scalp, head to your doctor for a diagnosis and safe recommendations for hair regrowth -- the same topical treatments that help with hair thinning are not recommended for hair loss associated with autoimmune diseases.

Many women who enter their doctor's office with complaints of hair thinning and hair loss often walk out with a thyroid disorder diagnosis. If your thyroid hormone levels are too low (hypothyroidism) or too high (hyperthyroidism), hair loss is a telling symptom that your levels are out of whack. "You'll usually find large amounts of hair falling out in the shower or sink, often accompanied by changes in the hair's texture -- drier than usual, more coarse or easily tangled -- these are all common symptoms of a thyroid disorder," Marotta explains.

Solve It:
If you suspect your thyroid is to blame, have your doctor check your thyroid levels, which can be done through a simple blood test. Fortunately, when it comes to hypothyroidism and hyperthyroidism, hair will return to its natural state once the thyroid imbalance is treated.