10 scary health symptoms that are (seriously!) harmless

© MSN Healthy Living // © MSN Health

If you pore through pages on the Internet for reasons behind every twitch, bruise or bump, you can easily convince yourself you have a serious health crisis. Cyberchondria, or Web-enabled hypochondria, only drives you crazy. Here, experts debunk some of the scariest but usually harmless symptoms with tips on when they may warrant concern.

-- By Linda Melone

1 of 12 Woman working on laptop by window (© Tripod/Getty Images)

Popping/creaking/cracking joints

Stretching, reaching or simply walking can trigger snaps, crackles and pops from a knee, shoulder or from your back. All that noise may sound scary, but it's usually nothing to worry about, says Jessica Matthews, an exercise physiologist with the American Council on Exercise. In fact, it may simply be gas. Specifically, fluid in your joints (which acts as a lubricant) contains dissolved gases such as oxygen, carbon dioxide and nitrogen. "Pressure changes within the joint causes these bubbles to burst within the fluid, creating a cracking or popping sound," says Matthews. Tendons shifting out of place as the joint moves and arthritis can also cause a popping sound.

See a doctor if pain or swelling accompanies the sounds.

2 of 12 Cracking knuckles (© Image Source/Getty Images)

Black toenails

Running for miles in shoes that fit poorly can cause toes to bump up against the top of your shoe, making the toenail turn a frightening shade of black. It may look morbid, but "runner's toe" is simply the result of the skin underneath the nail bruising and bleeding, says Matthews. "This causes the blood to pool under the nail with every stride. It's usually harmless but can be very painful." Avoid it by getting shoes properly fitted. Matthews suggests getting fitted for shoes at the end of the day, when feet are largest.

See a doctor if pain, swelling and redness appear, which may be signs of an infection.

3 of 12 Close up feet (© Altrendo Images/Getty Images)

Muscles shake during exercise

New exercises or increasing exercise intensity may cause muscles to shimmy and shake. No need to worry, your muscle fibers simply have to synchronize, says Matthews. "Essentially, not all muscle fibers contract at the same time, as they trade off duties during movement (some rest while others work and vice versa)." Shaking occurs as the muscle approaches its limits and not enough of the muscle fibers are contracting to allow for continued smooth movement. "The shaking will subside as you become accustomed to the new demands," says Matthews. Dehydration may also cause shaking.

See a doctor if you experience pain or dizziness along with the shaking.

4 of 12 Men exercising in a gym (© Glow Wellness/Getty Images)

Eyelid twitch

An involuntary, twitchy eyelid can be more annoying than anything but is a harmless condition called myokymia, says Dr. Sandy T. Feldman, an ophthalmologist and founder of ClearView Eye & Laser Medical Center in San Diego. "Like any other muscle twitch, it's usually due to stress, fatigue or lack of sleep." Too much caffeine, drugs and alcohol, too much time on the computer or an improper glasses prescription may also contribute to a twitchy eye. If eye fatigue is the issue, a pair of prescription reading glasses may bring relief. You can also try antihistamines.

See a doctor if other symptoms emerge, such as a coinciding facial twitch, which could indicate a neurological disorder, says Feldman.

5 of 12 Closed eye (© I Love Images/Getty Images)

Skin tags

Small pieces of skin on an eyelid or other part of the body called skin tags (acrochordon) are actually small benign tumors, says Dr. Debra Jaliman, a New York-based dermatologist and the author of Skin Rules: Trade Secrets from a Top New York Dermatologist (St. Martin's Press, 2012). "They're often genetic and are usually harmless." Both men and women are equally prone to developing skin tags, though obesity and pregnancy increases the chances of developing them.

See a doctor if you notice a sudden rash of skin tags, as they may be a precursor to colon cancer, says Jaliman.

6 of 12 Skin tags (© Medical-on-Line/Alamy)

Hand tremors

If you notice your hand shaking as you raise a glass of water to your lips but not while you're relaxed, don't panic. You may have a harmless condition called essential tremors. "Essential tremors are confined only to tremulousness without other neurological symptoms," says Dr. J. Eric Ahlskog, a neurologist with the Mayo Clinic. Typically, essential tremors involve the hands when holding a fork, knife or spoon, while Parkinson's tremors occur during a relaxed state, such as when the arms are down to the side, says Ahlskog. Essential tremors may also affect the voice or the head and are fueled by adrenaline, so excitement or anger may worsen symptoms.

See a doctor if tremors become severe (treatment is available) or if they are accompanied by other neurological symptoms, such as changes in speech.

7 of 12 Man looking at hands (© Purestock/Getty Images)

Vertical fingernail ridges

Nail ridges, tiny raised lines that extend from the cuticle to the tip of the nail, are similar to wrinkles on the face, says dermatologist Jaliman. "They're brought about by age and are not a sign of any medical condition." It is known medically as onychorrhexis, a name which translates to "brittle nails," which often accompany these vertical ridges.

See a doctor if the ridges are horizontal or if your nails are otherwise discolored or distorted, as it may be a symptom of something more serious, says Jaliman.

8 of 12 Woman using lotion on nails (© Henry Arden/Getty Images)

Eye Floaters

The appearance of dots before your eyes that float about in your field of vision often occurs in nearsighted people and is not usually a cause for concern unless it occurs suddenly. "These 'floaters' are typically caused by age-related changes in the jelly-like substance (vitreous) of the eye," says ophthalmologist Feldman. Floaters develop when the vitreous thickens and shrinks, which occurs during middle age. They may appear as dots, squiggly lines, cobwebs or circles and become more noticeable when looking at a plain background such as a blank wall.

See a doctor if you notice a new onset of floaters, a shower of floaters, flashing lights or a shadow or curtain comes across your eye, says Feldman.

9 of 12 Man with sunspots (© Adrian Samson /Getty Images)

Broken blood vessels in the eye

A red splotch in the white part of the eye looks as if you've been punched but is not usually cause for concern unless it happens often. "Rubbing the eye too hard, a pillow rubbing up on the eye while you are sleeping, sneezing hard, and constipation (straining) are the common causes of a broken blood vessel in the eye," says Dr. Elio Polsinelli, Jr., an optometrist with the California Optometric Association. Anticoagulants (blood thinners) and too much Omega-3 can cause broken blood vessels. "Uncontrolled hypertension can also be behind repeated broken blood vessels in the eye," says Feldman.

See a doctor if you notice recurring broken blood vessels, as it could indicate uncontrolled hypertension and should be addressed, says Feldman.

10 of 12 Close up of eye (© Adrian Samson/Getty Images)