Why does my hair turn green from the swimming pool

Swimming pools offer a refreshing respite during hot summer days, but for some individuals, a dip in the pool may lead to an unexpected phenomenon: green hair. This perplexing occurrence has puzzled swimmers for years, prompting questions about its causes and potential remedies. To understand why hair turns green in swimming pools, we must delve into the complex interplay between pool chemicals, particularly chlorine, and trace elements like copper. This article aims to unravel the science behind this curious transformation in approximately 1000 words.

Chlorine and Hair:

Chlorine is a common disinfectant used in swimming pools to kill harmful bacteria and pathogens, ensuring a safe and hygienic swimming environment. When chlorine is added to pool water, it undergoes chemical reactions that produce hypochlorous acid and hypochlorite ions. These reactive species effectively sanitize the water by destroying organic contaminants, including sweat, oils, and bacteria, thereby preventing waterborne illnesses.

However, chlorine’s sanitizing properties come with unintended consequences for swimmers’ hair. Human hair is primarily composed of a protein called keratin, which contains sulfur-containing amino acids. Chlorine, in its reactive forms, can oxidize these sulfur compounds in hair proteins, leading to chemical changes that manifest as discoloration. As chlorine interacts with keratin, it may weaken the hair’s structure and strip away its natural oils, making it more susceptible to damage and discoloration.

The Oxidation Process:

The process by which chlorine turns hair green is primarily oxidative in nature. When chlorine reacts with the proteins in hair, it oxidizes the sulfur atoms within the keratin molecules. This oxidation alters the chemical composition of the hair, causing it to take on a greenish hue. The precise mechanism of this reaction involves the formation of sulfur-containing compounds, such as thiosulfate and sulfite ions, which contribute to the green discoloration of the hair shaft.

Furthermore, prolonged exposure to chlorinated water can exacerbate this effect, as repeated oxidative reactions continue to modify the hair’s structure and color. Individuals with lighter or porous hair may experience more pronounced discoloration due to increased penetration of chlorine into the hair shaft.

Copper Contamination:

While chlorine plays a significant role in causing green hair, another element often contributes to this phenomenon: copper. Copper is a common trace element found in many water sources and can enter swimming pools through various means, including corrosion of copper plumbing, algaecides containing copper compounds, or even natural environmental sources.

Once present in pool water, copper ions can interact with chlorine and hair proteins, intensifying the green discoloration effect. Copper ions act as catalysts for oxidation reactions, accelerating the breakdown of keratin and enhancing the formation of green-colored compounds. Consequently, pools with higher copper concentrations are more likely to cause green hair, especially when combined with elevated levels of chlorine.

pH and Water Chemistry:

The pH level of pool water also influences the likelihood of hair discoloration. Chlorine is most effective at sanitizing water when the pH is within a specific range, typically between 7.2 and 7.8. Outside this range, chlorine’s reactivity and ability to oxidize contaminants may vary, impacting its interaction with hair proteins. Additionally, extreme pH levels can affect the solubility of copper ions, potentially leading to increased deposition on hair surfaces.

Preventive Measures:

While green hair can be an unwelcome consequence of swimming in chlorinated pools, several preventive measures can help minimize its occurrence:

Pre-swim Conditioning: Applying a protective barrier, such as a leave-in conditioner or coconut oil, to hair before swimming can help reduce its exposure to chlorine and mitigate oxidative damage.

Wearing Swim Caps: Using a swim cap creates a physical barrier between hair and pool water, limiting direct contact and minimizing chlorine absorption.

Rinsing After Swimming: Immediately rinsing hair with fresh water after swimming can help remove residual chlorine and copper ions, reducing the likelihood of discoloration.

Using Clarifying Shampoos: Clarifying shampoos specifically formulated to remove chlorine and mineral buildup can help restore hair’s natural color and vitality.


In conclusion, the green discoloration of hair in swimming pools is a result of complex chemical reactions involving chlorine, copper, and hair proteins. Chlorine oxidizes sulfur-containing compounds in keratin, leading to alterations in hair color and structure. Additionally, copper contamination can exacerbate this effect by catalyzing oxidation reactions and intensifying discoloration. Understanding the underlying chemistry of green hair can empower swimmers to take proactive measures to protect their hair and enjoy the benefits of swimming pools without unwanted side effects.

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