To address consumer concerns about the strong smell and irritation caused by ammonia, many companies now market chemical hair colors labeled as “ammonia-free” as gentler or safer alternatives. However, scientific evidence suggests that replacing ammonia with other alkalizing agents—such as Monoethanolamine (MEA) or Aminomethyl Propanol (AMP)—does not necessarily make these products less damaging. In reality, “ammonia-free” does not mean “damage-free.” These alternative chemicals used in chemical hair colors still raise the hair’s pH to allow color penetration and, in some cases, may cause equal or even greater structural damage to the hair than ammonia itself (Bailey, et al).

Monoethanolamine (MEA): The Hidden Cost of “Ammonia-Free” Chemical Hair Colors

Since it does not evaporate easily, MEA can remain on the hair and scalp even after rinsing, leading to prolonged exposure (Bailey, et al). Scientific studies using techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and protein analysis have shown that MEA can cause significant damage to hair fibers. Research has found that exposure to a 5% MEA solution can result in severe surface damage and breakdown of hair proteins (Ali, et al). Mechanical testing has also shown that hair treated with 5% MEA can lose about 25% of its strength after just one hour of exposure, with prolonged exposure leading to around a 50% reduction in mechanical strength (Ali, et al). Some comparative studies have reported that MEA-based formulations used in chemical hair colors may cause substantially greater structural damage and protein loss than comparable ammonia-based systems under certain test conditions (Bailey, et al). This damage can leave hair more porous, weaker, and more prone to breakage (Bailey, et al).

In addition, studies suggest that the combination of MEA and hydrogen peroxide, commonly used in chemical hair colors, may increase oxidative stress and cellular damage in human keratinocytes and may contribute to skin irritation and dermatitis. In some cases, such damage has been associated with chemically induced hair shedding, including telogen effluvium (Zanoni, et al).

Aminomethyl Propanol (AMP): A Growing Safety Concern in Chemical Hair Colors

Although AMP was previously considered safe at low concentrations, recent toxicological assessments have raised significant concerns. The European Chemicals Agency (ECHA) Committee for Risk Assessment (RAC) has proposed a harmonized classification of AMP as a Reprotoxic 1B (CMR) substance, indicating that it may be toxic to human reproduction (Palaniappan, et al). In addition, the RAC has classified AMP as corrosive to the skin, capable of causing serious eye damage (Category 1), and harmful to the liver after repeated exposure (Palaniappan, et al). As a result, AMP is on a regulatory path that could lead to its prohibition in cosmetics in the European market under Article 15 of the Cosmetics Regulation, highlighting the potential risks associated with some “ammonia-free” chemical hair colors (Palaniappan, et al).

PPD and Chemical Hair Colors: Understanding the Allergy Risk

When PPD, a common ingredient in chemical hair colors, comes into contact with the skin, it can bind to skin proteins and trigger an immune response. The body’s immune system creates memory cells that recognize PPD, meaning that once a person becomes sensitized, future exposure can cause an allergic reaction (Zanoni, et al). This reaction, known as Allergic Contact Dermatitis (ACD), usually appears within hours or days after exposure. Mild symptoms may include itching, dryness, and rashes around the scalp, ears, or eyelids (Palaniappan, et al). In more severe cases, it can cause redness, blistering, fluid-filled skin lesions, and significant swelling of the face and neck (Palaniappan, et al).

In rare but serious cases, PPD allergy associated with chemical hair colors may lead to widespread skin reactions, breathing difficulties, asthma, kidney problems, or even anaphylaxis, a life-threatening allergic reaction (Zanoni, et al). Once someone develops a PPD allergy, it is generally lifelong, and repeated exposure to chemical hair colors containing PPD can trigger increasingly severe reactions (Palaniappan, et al). People who are allergic to PPD may also react to related chemicals found in textile dyes, local anesthetics, and some cosmetic ingredients due to cross-sensitization (Zanoni, et al).