How Nail Biting Causes Infections

Nail biting is more than just a bad habit. It can cause diseases. Most of the serious diseases associated with nail biting is a result of infections. It is not just the fingers that can become infected. Nail biting may lead to infections anywhere on the surface of the body and even internally. Most nail biters do not realize just how unhygienic the practice can be but more so how dangerous it may be. Some of these infections that arises with nail biting can be very serious and even lead to severe diseases that may be fatal without the proper treatment.

Contamination of the Nails

Biting your nails has a host of effects beyond the visible aspects.

  • Biting causes a jagged surface on the tip of the nails. It may not be clearly visible but the roughness can often be felt.
  • The teeth may also injure the nail bed and the skin on the sides of the nails. It may lead to breaks in the skin that is not always evident.
  • In the process of nail biting, bacteria from the mouth is transferred to the nail surface and skin on the fingertips.
  • Saliva being sticky in nature can also trap dust and microbes from the environment.

Due to the various effects of nail biting, an infection becomes likely for several different reasons depending on the site of the infection. We will look at some of the common localized infection caused by nail biting. However, nail biting can cause systemic infections. This means that many areas in the body are infected simultaneously. It is well known that nail biters are also more prone to contracting common human infections like the flu and cold.

Fingertip Infections


Nail biting can lead to infections of the skin lying around the nail. This is known as paronychia. It is mainly caused by bacteria or fungi. During the course of biting the nails, the teeth may injure the skin unintentionally. However, many biters also tend to bite at the surrounding skin or pick at it with their fingers.  The injury compromises the integrity of the skin and bacteria or fungi can the invade the tissue. Since the hands and especially the fingers are in contact with various surfaces and substances during the course of the day, the area is easily infected.

Even the normal skin flora, the bacteria that naturally live on the skin, will quickly infect the exposed area. Bacteria from the mouth may also be highly pathogenic. This means it can cause serious infections yet it is able to reside in the mouth without causing a problem in most instances. The reason that these bacteria may not be a problem in the mouth is that it is kept in check by other species of bacteria also residing in the mouth as well as saliva. However, once these bacteria make contact with the broken skin, it can quickly infect the exposed tissue of the fingertips.

Skin and Eye Infections

Even if you do not have skin diseases, it is only natural to scratch your body several times in a day. Often it is just gentle scratching and the itch, if present, is quickly relieved. Sometimes it is just a habit or a sign of nervousness. But when scratching with the fingertips that have jagged nails, even slight pressure can cause tiny tears in the skin. These tears may not be visible. It may not even pain or bleed. But it may be sufficient to create an entry point for bacteria and fungi to infect your skin. It may result in serious infections like impetigo which can then extend into deeper tissues causing cellulitis.

The eyes are just as prone to injury to the jagged bitten nails. We rub our eyes and even gently scratch our eyelids several times in a day often without realizing it. The skin on the eyelids are thin and the tissue of the eyes are very delicate. Injury and infection may lead to conditions like blepharitis, conjunctivitis and keratitis. The risk is much greater in contact lens wearers who have to make close contact with the eye to insert and remove the lenses. Sometimes the bitten fingernails may contaminate the contact lens and even cause it to tear which then injures the eye and implants the microbes from the fingers.

Mouth and Gut Infections

Countless microbes enter the gut through the mouth. These microbes may be in the food that we eat and fluids that we drink. It may be on the utensils that we use and on our hands when we feed ourselves. However, it is usually in small amounts and most dangerous microbes are not present if we practice proper hygiene and consume foods or drinks from reputable sources. Most of us wash our hands prior to eating. But nail biters do not practice this level of hygiene when they partake in their habit. Therefore the chances of introducing microbes from the environment that are not likely to enter the mouth under normal circumstances is high in nail biters.

The microbes can infect the mouth but the mouth has several mechanisms to prevent this from occurring. An infection can also arise in the gut once these microbes travel further down. Although the stomach acid is able to kill even large amounts of different microorganisms, some can survive the highly corrosive environment. In this ways microorganisms from the environment, either in the air or settled on objects (fomites), can enter the mouth and cause infections of the gut. A simple handshake, pressing a button or touching a doorknob and then biting the nails afterwards can introduce these microbes into the body.

Ways To Avoid Infections from Nail Biting

bitten nails

The best way to avoid infections is to stop biting the nails. However, it is often easier said than done. Here are some tips to reduce the chances of an infection if you are a nail biter.

  • Apply bitter-tasting nail polish on your fingers. Although nail biting is a compulsion that needs to be treated with behavioral therapy, the nail polish will at least minimize your nail biting.
  • File your nails regularly if you are a nail biter. Keep it smooth but remember that this does not make up for a habit that needs to be stopped.
  • Trim your nails before you can bite it. Although your biting is trimming it as well, some nail biters do not bite their nails on a daily basis.
  • Wash your hands thoroughly before and after you bite. Just as much as nail biting became a habit, you may be able to develop a routine of good hygiene that can also become a habit.
  • Carry a hand sanitizer so that you can at least disinfect the fingers regularly if you unconsciously bite your nails.
  • Think about where your hand has been before you bite. Does it have fecal particles that you picked up from a contaminated object? How many thousands or even millions of microbes are on your fingertips? If you regularly think about these issue, it may discourage you from nail biting.

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