Nail hardeners work to harden and solidify breaking, brittle, splitting, or peeling nails by either strengthening the nail from within or forming a thick protective coating on the surface.
DEFINITION: What are nail hardeners?
A nail hardener is a cosmetic formulation that is applied to brittle fingernails to make them more resistant to breakage and prevent splitting and peeling. Nail hardeners are also referred to as nail strengtheners. Its important to differentiate that there is another type of nail product that strengthens nails called a nail conditioner. Nail conditioners are different than nail hardeners in that they moisturize with oils and nourish with vitamins but do not harden. Nail hardeners, however, contain substances that harden and solidify either within the nail itself or on the surface of the nail.
HISTORY: What is the origin of nail hardening?
The first known interest in hardening of the fingernails came about in the United States around 1792 with a combat sport called “rough and tumble”. Participants would engage in gouging their opponent with their fingernails. In preparation for the fight, they would harden their fingernails by holding them over an open flame. Much later, in the 1960s, with a growing and expanding cosmetics industry, nail hardeners entered the market with a formulation containing a minimum of 10-percent formaldehyde solution. Later, the FDA (Food and Drug Administration) recalled these products due to reported illnesses and set guidelines requiring concentrations of formaldehyde not to exceed 2-percent in nail hardening products. The 2-percent restriction is still in place today.
BODY ELEMENTS: What makes nails brittle?
A fingernail has three main parts: the nail bed, the nail matrix, and the nail plate. The nail bed is the skin underneath the nail that contains the blood supply that delivers proteins and nutrients to the nail matrix. The nail matrix, found at the base of the nail, uses those proteins and nutrients to create mostly keratin protein cells. As the keratin is produced, the older keratin cells push forward and become compressed, flat, and translucent forming the nail plate (the hard part of the nail). It is the nail plate that can become brittle and break off, peel, or split. Peeling usually occurs in horizontal layers whereas splits occur lengthwise in the nail. The condition of brittle nails, which includes splitting and peeling, is referred to as onychoschizia.
Brittle nails can be either dry and brittle, unable to maintain enough moisture, or soft and brittle, experiencing an excess of moisture. To determine if environment is the cause of brittle fingernails, the fingernails should be compared to the toenails. If the toenails are strong, then the brittleness is caused by an external factor. External factors can include washing or bathing, changing levels of temperature and humidity, exposure to chemicals, or picking off nail polish. Washing or bathing causes brittleness due to the fact that fingernails are extremely absorptive, actually ten times more so than skin. As the water absorbs into the nails, the keratin cells expand. On drying, the nail cells contract. This repeated expanding and contracting results in brittleness of the nail. The same type of strain (from expanding and contracting) can occur when the humidity levels in surroundings change, often due to a change in outside temperatures. Chemicals found in detergents, cleaning products, and nail polish removers can dry or damage the nails and cause brittleness. Of note, acetone-free nail polish removers are only somewhat less offending than acetone containing removers. The use of alcohol sanitizers can cause drying and, therefore, brittleness of the nails. An unfortunate habit of picking off nail polish also can cause brittleness; along with the nail polish goes the topmost layers of keratin cells. There are other reasons for unhealthy brittle, peeling, or splitting nails, however, those will be discussed later on.
FUNCTIONS: How do nail hardeners work?
There are two types of nail hardeners: cross-linking nail hardeners and reinforcing nail hardeners. Cross-linking nail hardeners actually penetrate the nail and change the framework of the nail’s keratin (protein) providing more structural support from within. Reinforcing nail hardeners do not penetrate the nail and serve to coat the nail’s surface with a thick, hard or flexible, protective covering. Reinforcing hardeners do not permanently alter the condition of the nail like cross-linking hardeners do. Once a reinforcing hardener is removed, the nail returns to its previous state. (Note: For the purposes of explanation, reinforcing hardeners have been further subcategorized by function in this hub.)
The nails are almost entirely made of keratin (protein) fibers, and those fibers (protein chains) form a matrix of linkages within the nail plate. A cross-link is a bond that links one protein chain to another protein chain by forming a bridge between the two. Chemical substances can cause cross-linking to take place. The most prevalent chemical substance used to increase the number of cross-link bonds within the nail plate (thereby thickening the nail) is formaldehyde/formalin. Formaldehyde/formalin penetrates the nail plate and chemically reacts to the protein (keratin) naturally found there causing an increase in the amount of bonds (bridges) between the protein chains. This makes the nails harder.
A note about formaldehyde/formalin – The INCI (International Nomenclature of Cosmetic Ingredients) requires that manufacturers list formalin under the name formaldehyde. Although formalin does contain a trace level of formaldehyde (formalin is actually derived from the combination of water and formaldehyde to form an entirely different substance), it is kept at safe levels according to the FDA standard of no more than a 2-percent solution of formaldehyde in nail hardening products. Most nail hardeners contain formalin, not formaldehyde. And, even though deemed safe by the FDA, that does not address the issue of allergic reactions to formaldehyde/formalin on contact with the skin. In addition, formaldehyde/formalin is an aggressive cross-linking agent. Too many cross-links in the nail plate can cause the nails to become overly hardened and result in breakage and brittleness. It is recommended that formaldehyde/formalin nail hardeners only be used periodically or alternated with a non-hardening base coat.
A second chemical substance that can cause cross-linking to take place within the nail plate is DMU (dimethyl urea). It works in exactly the same fashion as formaldehyde/formalin but has two advantages over it. 1) DMU does not create excessive cross-links from frequent use and over harden the nail plate. And, 2) DMU is less allergenic (prone to allergic reactions).
Reinforcing Surface Bond Hardener
Although the nail plate is made mostly of keratin proteins, there are deposits of the mineral calcium that attach to the keratin. Fluoride is a chemical substance that bonds to calcium molecules. Applying a nail hardener that contains fluoride results in chemical bonds being formed between the fluoride in the product and the calcium found naturally occurring in the nail plate. CaF (calcium-fluoride) bonds take place on the surface of the nail. Fluoride does not penetrate the nail keratin like the cross-linking hardeners do.
Reinforcing Protein Web Hardeners
A protein is composed of a long chain of amino acids bonded together (called a peptide bond) to form a filament (fiber). Protein hardeners such as keratin form a web-like network of interlacing protein filaments (fibers) on the surface of the nail. In addition, peptide bonds in proteins can be broken down through a process called hydrolysis into individual amino acid units. Hydrolyzed grain and vegetable proteins, such as soy, wheat, and corn, are also formulated into nail hardeners. Because they have been hydrolyzed, their protein peptide bonds have been broken down into individual amino acids or partially joined amino acids that are floating in the product. Upon application of the product, the amino acids re-bond to form new protein filaments (fibers) and create a web-like network on the surface of the nail. These filaments (fibers) are microscopic but do harden the nail. Protein hardeners do not penetrate the nail because their molecules are too large to do so.
Reinforcing Fiber Web Hardeners
Some nail hardeners contain micro-fibers made of nylon, silk, or fiberglass. These function in the same way that protein hardeners do; they form a web-like network of interlacing fibers on the surface of the nail. The micro-fibers are chosen for their strength. Nylon is a tough, elastic, synthetic polymer that has a chemical structure similar to proteins. Silk is a naturally occurring material that is produced by insects and is known to be strong and resistant to breakage. Fiberglass is made of glass fibers and is strong and non-brittle.
Reinforcing Mineral Shield Hardeners
Mineral hardeners form a hard, protective shield on the surface of the nail and are made of minerals such as diamond powder or calcium. Diamonds are considered the hardest known substance. Calcium is what makes bones strong and hard. Both minerals form a hard, thick shield on the surface of the nail for reinforcement.
TABLE: Summary of Nail Hardening Ingredients
|Ingredient||Type of Hardener||Function of Hardener|
DMU (dimethyl urea)
hydrolyzed corn protein
hydrolyzed soy protein
hydrolyzed vegetable protein
hydrolyzed wheat protein
AUDIENCE: Who would benefit from a nail hardener?
In addition to the environmental factors, mentioned previously, that cause brittleness, a medical condition can be the cause of breaking, splitting, and peeling. Those medical conditions include:
- thyroid disease
- eating disorders
- protein deficiency
- iron deficiency
- lung disease
- Raynaud's disease
- Sjogren's syndrome
- psoriasis and other skin diseases
- endocrine disorders
Persons who do not have any of these medical conditions and have ruled out environmental factors may have brittle nails as the result of heredity (genetics) or simply aging. It is estimated that approximately 20-percent of the population suffers from brittle nails.
There are two types of nail hardeners on the market for persons who suffer from brittle nails. Those that cross-link proteins within the nail, and those that reinforce the nail by forming a thick, protective coating on the surface. The benefits of nail hardeners are that they remedy brittle nails that break, split, or peel.
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Nail Hardener Poll
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Author: Chrissy Candace
To read more articles on beauty, anti-aging, skin care, hair care, nail care, fragrances, bath & body, and cosmetics, follow me on my profile page.
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Jasmeet Kaur from India on August 09, 2015:
nice 1... voted up. I use by china glaze