If you notice pitting, or small depressions and dents on the surface on your nails, it might point to another skin disorder, Steele says. "Pitting on the nails is usually a sign of psoriasis," an inflammatory skin disease that typically causes scaly, itchy, red patches on the body. But if your body isn't tipping you off, pitting is another way those skin lesions show up, says Steele. "But it's also possible to have nail-only psoriasis," Steele adds. Your doctor can usually diagnose psoriasis with a straightforward physical exam and may recommend a topical treatment, oral or injected medication, or light therapy.

Brittle, cracked nails can ruin a good manicure, but there are bigger issues at stake here — namely, your thyroid gland. Your thyroid gland produces hormones and plays a major role in regulating your metabolism and energy. If it's underactive and hormone levels are low, it usually manifests as dry skin, hair that falls out, and very brittle nails that struggle to grow. If this is the case, ask your doctor for a quick blood test to find out if your hormone levels and thyroid are normal. On a less scary but still depressing note, brittle nails are also a classic sign of getting old, says Steele. "This is especially true of ridging and brittleness. The intrinsic moisture in the nail tends to decline with age, as it does the moisture in our skin."

If you have linear ridges, known in the medical world as Beau's Lines, your nails are trying to tell you something. You may be vitamin or mineral deficient (lack of zinc can cause the ridges), it could be a bad allergic reaction to a new polish, or something more serious, like diabetes. "Beau's Lines can be associated with anything that stresses the body and requires it to divert resources away from nail growth," says Steele. "This could be anything from a surgery, to severe illness, or a reaction to certain medications." Don't rush to WebMD to diagnose yourself; make an appointment with your doctor to find out of this is a minor reaction or a major health concern.

If your nail folds are red, swollen, and tender, chances are you have an infection, According to Steele, puffy nail folds tend to occur with a condition called paronychia, but don't let the big name scare you. Paronychia is a skin infection that occurs around the nails and is fairly common. It can be caused by a bacterial or fungal infection from everyday trauma and inflammation — think: nervously gnawing your cuticles, picking a hangnail, or simply over-washing your hands.

Clubbed nails are hard to miss, and they are not to be taken lightly — this nail condition can signal a serious illness, says Steele. "Clubbing of the nails is typically a sign of long-standing or severe cardiovascular or lung disease and poor oxygenation," says Steele. And the list only goes on — clubbed nails can also signal cyanotic congenital heart disease, cystic fibrosis, and chronic inflammatory bowel disease. All of these diseases cause the small arteries in the fingertips to dilate, which enlarges the tissues of the nail beds and causes the fingernails to club.