Your hands, elbows and lips aren't the only parts of your body that dry up during the winter months — your scalp is also vulnerable. So, if you notice more white flakes on your shirt than on the ground, you're probably suffering from dandruff.

It's one of the most common and chronic conditions that affect the scalp.

"There are grades of dandruff," said Dr. Doris Day, an attending dermatologist at Lenox Hill Hospital in New York and author of Forget the Facelift. "There's mild cases, moderate, severe and sometimes it's just a little bit of dry skin."

For most people who've had dandruff — the signs are clear.

"Typically, you have a red, itchy scaling scalp," said Day. And while these symptoms seem pretty straight forward, there are several conditions that can lead to the often embarrassing white flakes.

"It could be psoriasis or reaction to a product you're using," Day said.

Psoriasis is a chronic and non-contagious disease that affects the life cycle of skin cells. It most commonly appears on your knees, elbows and torso, but it can also show up on your scalp.

"A lot of people who assume they have dry scalp actually have dermatitis, which is actually not dry scalp," said Dr. David Horne, a dermatologist at a private practice in New York City. "It's actually an inflamed scalp."

As Horne said, seborrhea dermatitis is an inflammatory skin condition that causes flaky, white to yellowish scales to form on the scalp. It can also affect other areas rich in oil glands, including the eyebrows, the sides of the nose and inside of the ears.

"There's really no cure for dandruff because we don't know exactly what it is," said Day. "We're still sorting through it all. It may not be just one thing."

That said, dandruff is easy to control and there is an array of products available in drug and grocery stores.

Day described several options:

— Look for sulfur-based shampoos such as Head and Shoulders and Selsun Blue.

— Tar-based products are also a good option. Day recommends Neutrogena T-Gel.

— Neutrogena T/Sal shampoo, which contains salicylic acid, is also ideal to help reduce excess flaking, she said.

"Use the shampoo everyday until it clears," recommended Day. "Then you want to use them once a week and then every other week to keep it clean."

She also stressed the earlier you treat the dandruff the better.

"Don't wait until it gets bad every time because these are chronic conditions. If you see it coming back, treat it early."

If over-the-counter solutions aren't doing the trick, it might be time to take a trip to the doctor.

"If it doesn't clear up in two weeks, it's time to call your dermatologist," said Day. "Especially if you have associated hair loss and other symptoms such as sores on the scalp, pain and excessive itching."

After you visit a specialist, they will most likely prescribe topical cortisones or an anti-fungal shampoo that helps kill yeast.

Remember the skin is our largest organ, noted Day. "It's constantly regenerating which means we're shedding skin cells everyday."