Isla Bennett
The nail is a protective plate found at the tip of the digits (fingers and toes) of all primates. The nail plate, or nail body, is the hard nail area from the nail root to the free edge, made of translucent keratin protein. Keratin is a fibrous, tough, insoluble protein that forms a structural element of fingernails. It contains large amounts of sulfur, with the organic element occurring almost exclusively in amino acids of the nail plate. The nail matrix is the active tissue that generates nail plate cells, which are pushed outward and harden to become the nail plate.
| Characteristics | Values |
|---|---|
| Composition | Keratin, a scleroprotein (fibrous protein) |
| Keratin composition | 3% sulfur, 7% hydrogen, 14% oxygen, 15% nitrogen, 45% carbon, 8–10% inorganic components |
| Sulfur compounds | Responsible for the pungent odour after cutting nails |
| Exposure to toxic agents | Decreases the sulfur content in nails |
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What You'll Learn
Keratin proteins in nails contain sulfur
Keratin is a protein that the human body produces naturally. It helps form hair, nails, and skin. Keratin is strong and can be found in the hair, epidermis, horns, and nails of mammals. The human body contains 54 types of keratin, with 28 of them being Type I and the other 26 being Type II. Type I and Type II keratins are alpha-keratins, which are present in humans and other mammals.
Occupational exposure to harmful chemical agents can alter the organic elemental composition of fingernails and decrease sulfur levels. Painters and hairdressers, for example, are in frequent contact with chemical agents that can alter the organic structure of their fingernails. Painters are exposed to organic solvents, while hairdressers are exposed to oxidants, reducing agents, dyes, pigments, and bleaching agents. These substances can affect the keratin structure and composition, leading to decreased sulfur levels in the nails.
The importance of sulfur to nail hardness has been studied using analytical electron microscopy. It was found that the free surfaces of nails adsorb a significant amount of calcium from the environment, possibly due to ion exchange. The uniform distribution of sulfur across the nail cross-section suggests its role in maintaining nail hardness.
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Exposure to toxic agents affects fingernail composition
The human fingernail plate is highly keratinized, with the keratin structure held together by disulfide bonds. The organic elements sulfur and nitrogen occur almost exclusively in the amino acids of the nail plate. Occupational exposure to harmful chemical agents can alter the organic elemental composition of fingernails.
A study analysed the fingernails of 71 workers (49 hairdressers and 22 painters) who were occupationally exposed to solvents and other harmful chemical agents. The study found that the exposed group had significantly lower percentages of sulfur and higher percentages of carbon than the unexposed control group. This decrease in sulfur content is likely due to the destruction of sulfur-rich proteins in the nails caused by the destruction of disulfide bonds by alkaline and acid groups.
The occupational groups in the study reported frequent contact with chemical agents. Painters are mainly exposed to organic solvents such as benzole and acetone, which can alter or wash out proteins from their fingernails. Hairdressers, on the other hand, are exposed to oxidants, reducing agents, dyes, pigments, and bleaching agents, which can affect the protein structure of their fingernails. These agents contain substances like hydrogen peroxide and ammonium peroxodisulfate.
The C/S ratio has been proposed as a useful indicator of the amount of damage to nail proteins caused by harmful agents. Fingernails have been increasingly used in forensic science as they can retain a record of information on chemical exposure, drug use, pathology, diet, location history, and exposure to explosives or other pollutants.
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Fingernails can smell due to sulfur compounds
Fingernails are composed of keratin, a scleroprotein (fibrous protein) that contains large amounts of sulfur. The sulfur content in fingernails can vary depending on various factors, such as occupational exposure to harmful chemicals. For example, studies have shown that the fingernails of painters and hairdressers who are regularly exposed to solvents and other chemicals have significantly decreased sulfur content.
The edges of fingernails can trap dirt and residual smells, especially if they are long and not clipped regularly. This can lead to an odor, especially if the hands have not been washed properly after handling pungent substances like onions, garlic, or certain spices. In such cases, the solution is simple: trim your nails shorter and ensure you wash your hands and nails thoroughly, including the undersides of the nails.
However, if the odor persists even after proper hand and nail hygiene, it could indicate a health condition. For example, a fungal infection, known as onychomycosis, can cause a cheese-like odor. If the smell is accompanied by other symptoms such as redness, swelling, or pus drainage, it is advisable to consult a doctor for further evaluation and treatment.
The act of trimming the nails can also release a sulfur-like smell due to the disruption of the sulfur compounds present in the keratin proteins of the nails. This odor usually subsides after the trimming process. Additionally, friction from nails rubbing together, such as during rapid nail growth, can produce a similar sulfur odor.
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Sulfur content in nails may decrease due to occupational hazards
Fingernails are composed of high-sulfur keratins, with the element occurring almost exclusively in the amino acids of the nail plate. Keratin contains 3% sulfur, 7% hydrogen, 14% oxygen, 15% nitrogen, 45% carbon, and 8–10% inorganic components.
However, occupational exposure to harmful chemical agents can alter the organic elemental composition of fingernails, leading to decreased sulfur content. This was observed in a study of painters and hairdressers, who are routinely exposed to solvents and other chemicals. The study found a significant decrease in sulfur content in the fingernails of these professionals compared to unexposed individuals.
The destruction of disulfide bonds in keratin by alkaline and acid groups is believed to be the cause of the reduction in sulfur-rich proteins in the nails. This alteration in the nail's composition can be measured through the C/S ratio, indicating the amount of damage caused by harmful agents.
Occupational hazards related to nail dust and chemical exposure can have serious health consequences. Chronic exposure to nail dust, for instance, has been linked to allergic hypersensitivity, with cases dating back to the 1970s. Inhalation of nail dust can lead to asthma, rhinitis, or conjunctivitis, with symptoms such as coughing, wheezing, chest tightness, and watery eyes. Additionally, workers in nail salons are exposed to chemicals that can cause occupational asthma and other health issues. Proper ventilation, protective equipment, and safety protocols are crucial to minimizing these risks.
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Calcium and sulfur are important for nail hardness
Human nails are made up of keratin, a type of protein. Keratin is composed of several elements, including carbon, hydrogen, oxygen, nitrogen, and sulfur. The high disulfide bond content in nails, which comes from sulfur, is what gives nails their toughness.
Sulfur and nitrogen occur almost exclusively in the amino acids of the nail plate. The nail plate, or nail bed, is the hard keratinized surface of the nail. The keratin structure is held together by disulfide bonds.
Calcium is also important for nail hardness. The free surfaces of nails can absorb a significant amount of calcium from the environment through ion exchange. This is supported by the fact that the distribution of sulfur does not vary over the nail cross-section.
Overall, the presence of calcium and sulfur is crucial for maintaining nail hardness. These elements provide the structural integrity and toughness that characterize healthy nails.
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Frequently asked questions
Yes, the human fingernail contains sulfur.
Sulfur confers toughness to the nail. It is also responsible for the odor that is released when nails are cut or trimmed.
The nail plate is composed of keratin, a fibrous protein that contains large amounts of sulfur. Other components include sodium, potassium, nitrogen, magnesium, calcium, iron, copper, zinc, phosphorus, and selenium.
A persistent foul smell in the fingernails could be indicative of a fungal infection or another underlying medical condition. Exposure to toxic agents can also alter the organic composition of the fingernail, decreasing the sulfur content.
To prevent fingernails from smelling, it is important to maintain proper hand and nail hygiene. Trimming your nails shorter and wearing gloves while working or cooking can also help to prevent odors.
