Your hair turns green after swimming because of copper in the pool water, not chlorine. Copper ions bind to the proteins in your hair strands and create a green tint that’s especially visible on light or blonde hair. Chlorine plays a supporting role by damaging your hair enough to help it absorb more copper, but hair submerged in chlorinated water without copper doesn’t turn green at all.
Copper Is the Real Culprit
Most people blame chlorine for green pool hair, and it’s easy to see why. The green tint shows up after swimming in chlorinated pools, so the connection seems obvious. But experiments have shown that hair exposed to water containing only copper ions and no chlorine still develops a green color. Hair placed in chlorinated water without copper does not.
Copper ends up in pool water from several sources. Copper-based algaecides are one of the most common contributors, especially in residential pools where owners use them to keep water clear. Copper can also leach from metal pipes, heat exchangers, and well water used to fill the pool. Even small amounts are enough to stain hair over time, particularly with repeated exposure.
Once copper ions are in the water, they bind to the sulfur-containing proteins inside your hair strands. Electron microscopy studies have shown that copper concentrates in specific protein-rich layers of the hair cuticle. When these copper deposits oxidize, they produce a blue-green compound similar to the patina you see on old copper roofs or the Statue of Liberty.
How Chlorine Makes It Worse
Chlorine doesn’t cause the green color on its own, but it significantly amplifies the problem. Chlorine is an oxidizer, which means it strips electrons from your hair proteins. This damages the outer protective layer of each strand, opening it up and making it far more absorbent. Think of healthy hair as a closed pinecone and chlorine-damaged hair as an open one: the raised scales let copper ions penetrate deeper and bind more readily.
This is why the green tint tends to get worse over a summer of regular swimming. Each session strips away a little more of your hair’s natural protection, and each session deposits a little more copper. The effect is cumulative.
Why Some Hair Types Are More Vulnerable
Blonde and light-colored hair shows the green tint most obviously, simply because there’s less pigment to mask it. But the discoloration can happen to any hair color. On darker hair, the copper buildup may not look green, but it can create a dull, slightly off-tone cast.
Hair porosity is the bigger factor in how quickly the staining happens. High-porosity hair, where the outer cuticle layer is already lifted or damaged, absorbs copper ions much faster. Several things increase porosity: color-treated or bleached hair, heat styling, sun exposure, and chemical straightening or perming. If you’ve bleached your hair for summer, you’ve essentially created the perfect conditions for copper absorption. The same chemical processes that open the cuticle to accept hair dye also open it to accept metal ions from pool water.
Fine hair is also more susceptible than coarse hair because each strand has a higher surface-area-to-volume ratio, giving copper more contact points relative to the strand’s thickness.
How to Remove the Green Tint
Regular shampoo won’t do much because it isn’t designed to break the bond between metal ions and hair protein. You need a chelating shampoo, which contains ingredients that grab onto metal ions and pull them away from the hair strand. The most effective chelating ingredient is EDTA (you’ll see it on ingredient labels as disodium EDTA or tetrasodium EDTA). Sodium gluconate and citric acid also work as chelators, though they’re generally milder.
For mild cases, one or two washes with a chelating shampoo should noticeably reduce the green. For heavier buildup after weeks of swimming, you may need to use it several times over a week or two. Leave the shampoo on for a few minutes before rinsing to give the chelating agents time to work.
A popular home remedy is dissolving a few tablespoons of baking soda in water, applying it as a paste, and letting it sit for several minutes before rinsing. Ketchup and tomato paste are another folk remedy. The acidity of the tomato can help break down copper deposits, though results vary and a purpose-built chelating shampoo is more reliable. After any of these treatments, follow with a deep conditioner, because the removal process can leave hair feeling dry.
Preventing Green Hair Before You Swim
The simplest and most effective prevention step is wetting your hair thoroughly with clean tap water before getting in the pool. Hair is like a sponge: once it’s already saturated with fresh water, it absorbs significantly less pool water and the copper dissolved in it. This alone makes a noticeable difference.
Pre-swim hair products take this a step further by coating each strand with a protective layer of conditioning ingredients that act as a barrier between your hair and the pool chemicals. They work on the same principle as sunscreen: apply before exposure, not after. Look for products marketed specifically as pre-swim treatments, and apply them to wet hair for the best coverage.
A swim cap provides the most complete physical barrier, though it won’t keep your hair perfectly dry. Even a small reduction in water contact helps. After swimming, rinse your hair with fresh water as soon as possible. The longer pool water sits in your hair, the more time copper has to bind. If you swim regularly, using a chelating shampoo once a week as maintenance can prevent buildup from reaching the point where it becomes visible.
If your own pool is the problem, consider switching from a copper-based algaecide to a copper-free alternative. Chlorine-based shock treatments control algae without introducing copper into the water. Testing your pool water for copper levels can also help you identify whether pipes or your water source are contributing to the problem.