When wash day rolls around, you've probably got a checklist (be it literal or mental): shampoo, conditioner, hydrating mask, heat protectant, etc. One thing that probably isn't on that list is water.
Water is the ultimate unsung hero of hair washing—you can't get the job done without it, but it's so crucial you probably don't even think of it as a wash day component at all. As it turns out, however, your water temperature and quality play pretty big roles in the health of your hair and scalp.
To learn more about how H20 can make or quite literally break your strands, we turned to dermatologists Dendy Engelman, MD, FACMS, FAAD, Alexis Granite, MD, and Hasan Benar. Read on to learn more about how hot, cold, and lukewarm water can impact your hair health.
Meet the Expert
- Dendy Engelman, MD, FACMS, FAAD is a board-certified cosmetic dermatologist and Mohs surgeon at Shafer Clinic in New York City.
- Alexis Granite, MD, is a board-certified consultant dermatologist with expertise in general and cosmetic dermatology.
- Hasan Benar is an award-winning dermatologist and aesthetic doctor.
What Happens When You Wash Your Hair With Hot Water?
There are benefits to washing your hair with hot water; for example, higher temperatures open up pores, which helps shampoo and other products to penetrate the scalp. “Washing your hair with hot water may help remove dirt, grime, product, and oil more effectively than cold water,” Granite says.
Although higher temperatures make it easier for products to penetrate the scalp, hot water can strip the hair of its natural oils, which can lead to drying of the hair and scalp and cause irritation and itchiness. “The state of the scalp has an enormous impact on hair growth and health, so a dry, unhealthy scalp with dandruff can inhibit hair growth or weaken the strands,” Engelman explains. In addition to a dry and itchy scalp, washing your hair with hot water can also exacerbate conditions like seborrheic dermatitis and eczema.
According to Benar, washing your hair with hot water can transform the look of your hair, too: “When hot water is used to wash hair, your hair follicles are exposed to environmental and oxidative damage, which can lead to hair fall. Hair fall accelerates due to the loosened grip of the damaged hair roots. This can also result in premature greying, “ he says.
What About Washing Your Hair With Cold Water?
According to our experts, there are many pros—and a few significant cons—to washing your hair with cold water.
- Preserves natural oils: Unlike hot water, cold water doesn’t dissolve natural oils, which is beneficial for head and hair health and growth. “Keeping your hair’s natural oils helps limit dryness, itchiness, and irritation,” Engelman says.
- Increases shine: “Cold water works on the hair by closing cuticles and pores in the scalp, which increases hair's shine since the closing of pores retains moisture,” Engelman says.
- Added moisture: As cold water is able to close the pores of the scalp, the hair’s natural moisture levels are retained as well as any moisture you get from conditioners. As a result, the hair is able to better reap the benefits of the product, leaving it looking and feeling healthier and more hydrated.
- Helps with dandruff: Dandruff results from a dry scalp, and moisture is needed in order to treat it. “Since showering with cold water helps the scalp retain moisture, this will in turn alleviate dandruff and the irritation that comes with it,” Engelman explains.
- Improves blood circulation to the scalp: Although using cold water to wash your hair might feel uncomfortable at first, it can help the blood in the deep tissues of the scalp circulate more quickly. “This helps in maintaining an ideal body temperature as well as optimal health, such as health for the brain, heart, and healing processes of the body,” Engelman shares.
- Decreases volume: Cold water does an excellent job of helping hair retain moisture, but excess moisture can make the hair look flat and less voluminous. While this won’t happen to everyone, be mindful of how your hair reacts to cold water. Additionally, try not to use cold water when the weather starts to get colder, especially during winter.
- Excess moisture: “When hair retains moisture, it can leave too much oil in the head, and this can leave it looking and feeling greasy and flat,” Engelman says.
- Discomfort: Although it isn’t the worst con, cold water isn’t as comfortable and relaxing as hot or lukewarm water, and if you’ve never washed your hair with cold water before it will take some time to get used to it. “While cold showers can feel alarming and almost painful at times, the pros for skin, hair, and body health may outweigh the discomfort,” Engelman says.
What's the Best Temperature for Washing Your Hair?
Engelman and Benar recommend washing hair with lukewarm water. If you fancy reaping the benefits of a cold water wash, Engelman advises switching the water to cold toward the end of your shower to lock in moisture. According to Granite, warm water is the best temperature for washing hair. “If you have greasy hair, you could end with a hotter rinse to help remove oils and product more thoroughly,” she says.
In terms of a specific temperature, Benar recommends using water that is 100°F or 38°C (which is slightly above the normal body temperature) to wash your hair. “During the summer months, you can use water at a lower temperature,” he says.
How Does Water Quality Impact Hair?
Water quality can also impact hair—hard water in particular. "Hard water is water that contains a buildup of minerals like calcium and magnesium," Engelman explains. "It can leave a film on the hair that makes it harder to retain moisture, affecting the look and feel of your hair and potentially causing breakage since it will leave the hair dry."
Hard water, which is usually found in groundwater, can also increase hair shedding, "make hair look flat, and interfere with hair color, leading to brassiness,” Benar says.
If your hair is drier or duller than usual, chances are you're using hard water. As hard water has such a negative impact on hair, it’s useful to know how to counteract its effects. If DIY is one of your strong points, consider purchasing and installing a showerhead water filter. Clarifying shampoos, acidic rinses, moisturizing masks, and leave-in conditioners can also help remove mineral buildup and repair dryness.
The Final Takeaway
Whether you choose to wash your hair with hot water or cold, understanding the impact water can have on your strands is essential. While hot water does a great job of removing dirt and residue from your hair, it can cause dryness and irritation. Cold water doesn’t dissolve natural oils and boosts moisture levels, which promotes good hair health.
It’s important to note that not everyone will experience the best or worst that could come from washing your hair with hot water or cold, as hair care needs are unique to the individual. There isn’t a one-method-fits-all approach when it comes to washing your hair; it’s simply a case of trial and error. All you can do is be mindful of how your hair reacts to water of different temperatures and be willing to adjust if needed.