Finding the best keratin straighteners means checking whether the product has toxic ingredients such as formaldehyde, how long the straightening lasts, the cost of the treatments, the ability of the straighteners to combat dryness and whether the straighteners are formulated to suit a given hair type. It can be difficult to find the right balance of straightening, duration and safety, but checking formulations with health and cosmetic agencies can verify the claims of manufacturers. Typically, all-natural products are safest.
As with other cosmetic and beauty products, health is often a priority for consumers. The search for good keratin straighteners begins by checking that the hair treatments have no formaldehyde. This chemical is what keeps the keratin molecules together so the hair stays straight. At the same time, it is a known carcinogen that also causes issues such as irritation of the lungs and eyes. The recommended amount of formaldehyde in keratin straighteners is only 0.02 to 0.2 percent, but studies have revealed products with of 10 percent or more, far past the acceptable limit.
With formaldehyde a major reason why keratin straighteners work, consumers face a conundrum: they can get very straight hair by continuing to use a potentially harmful product, or they can buy formaldehyde-free products that are safer but do not produce hair that is as straight. Taking the assumption that preservation of health is more important than appearance, if a person opts for a formaldehyde-free product, she should check with agencies such as the Environmental Working Group to determine if the product truly is safe. Many manufacturers who claim their products are formaldehyde-free still use formaldehyde in the process, and even if the formaldehyde is not present, other toxic chemicals may be included in the formulation. In general, an all-natural or organic product is usually safest, although people still have to be cautious of particular allergies they may have.
In looking at the formaldehyde or formaldehyde-free debate, consider the duration of results. A product that uses formaldehyde typically lasts up to three months, while one without formaldehyde usually lasts about four to six weeks. In terms of cost, keratin straighteners are about the same regardless of whether they contain or leave out formaldehyde. Formaldehyde-free keratin straighteners are set at a lower price but the client has to come back more often.
One of the problems with curly hair is that the cuticle layer naturally is a little more roughed up. The curvature of the strand prevents the protein scales from sitting flat and overlapping as they should. Subsequently, moisture loss and breakage is a concern, particularly since the natural sebum from the scalp cannot travel as easily over roughed up cuticles in a curved strand. Hair straighteners often require massive amounts of heat — in excess of 400 degrees Fahrenheit (204.4 degrees Celsius) — to set the hair, which saps out moisture and makes the dryness problem worse. The best keratin straighteners can work with the flat iron on lower settings, or they compensate somewhat by including significant moisturizers.
Not all hair is the same. A mane can be fine, coarse, thick, thin, oily or dry, curly or straight. Different hair types need different things from hair straighteners to get the best results with minimal damage. Selection of a product thus entails checking that the formulation is appropriate for the hair type. Avoid products marketed for "all" hair types, as these do not take the structural differences between hair types into account.