Can Drinking More Water Help Hydrate Your Dry Skin?
How to hydrate your skin from the inside
First published: 11.Oct.2018
There is plenty of information on the internet and published in health or beauty magazines asserting that a higher water intake improves the skin's complexion by "moisturizing" it.
Another supposed benefit of drinking plenty of water is that the extra hydration will provide a dermatological detox, and "wash" or "flush" toxins away, cleansing pores, eliminating blackheads, and curing acne, scaly skin, dryness, and other skin conditions.
This detox effect is frequently coupled with another myth, the "8 x 8" rule (drinking eight 8-ounce glasses of water a day to stay healthy.)
In today's article, we will look into the facts and the science that supports or disproves the hydrating and detox effects of water on skin complexion.
Our Skin is a protecting barrier
The body's largest organ
Our skin covers approximately 22 sq. feet (2 m2) and weighs about 8 lbs. (3.6 kg), it is the body's largest organ.
The skin is the barrier that protects your body from the surrounding environment: it blocks the damaging ultraviolet radiation from the sun, helps regulate body temperature, insulates you, provides a waterproof coating, and keeps bacteria, toxins, and chemicals out of your body. It also prevents the body's water stores from evaporating away.
Its nerves provide you with sensation (pressure, pain, heat, and cold). Its cells synthesize vitamin D and provide a flexible envelope for the body's internal organs.
The skin is made up of three layers:
The epidermis is the outermost layer. It is a waterproof - protective wrapping for your body. It is made up of cells called "keratinocytes" that contain "keratin", a tough protein that also makes up your hair and nails.
The outermost layer of the epidermis, which is barely 1⁄50 inch. thick (0.5 mm) is known as the "Stratum Corneum" (or horny layer) and consists of dead cells that gradually flake off in a process known as "desquamation."
These cells form in the deepest layer of the epidermis and migrate outwards as they grow older. They are nourished by the oxygen that diffuses from the blood vessels located in the next layer beneath it, the dermis.
This is the second layer, beneath the epidermis. It contains fibers of collagen and elastin, two proteins that give it flexibility and support.
The blood vessels in the dermis regulate body temperature; an increased blood flow allows heat to radiate away from the body through the skin, cooling it, or, during cold weather, by restricting the flow it helps retain body heat.
The hair follicles are rooted in the dermis and the sweat and apocrine glands are located there too.
This is the innermost layer of the skin, it is also known as "hypodermis". It contains a layer of fat, used for both storage and insulation purposes (subcutaneous fat).
Water and the Skin
The body loses water by evaporation. Water moves upwards through the skin's layers: the hypodermis, the dermis, and it reaches the epidermis. There it works its way through the barrier formed by the Stratum Corneum (SC) and is lost into the atmosphere. This loss is known as "transepidermal water loss or TEWL for short.
When the skin's barrier is breached by chemicals, burns, bites, or mechanical damage, germs find their way into the body, causing it to lose fluids through the wound.
Fluid loss through burned skin can be quite large. Dr. Charles R. Baxter (1929-2005) devised a formula to work out the "extra" fluid intake necessary for burn patients to remain adequately hydrated.
For instance, a person that weighs 165 lbs (75 kg) with burns covering 20% of their body would need to drink an extra 1.58 gallons (6 liters) of fluids per day to keep hydrated.
Dryness, water, and skin flaking
The water content in healthy Stratum Corneum (SC) - the outermost layer of the skin- is about 10%, and it has a role in the normal "desquamation" process by which the external dead skin cells are shed from the skin (1).
The Skin's Natural Moisturizing Factor
The water in the SC contains some water-binding substances known collectively as Natural Moisturizing Factor (or NMF for short).
NMF contains amino acids (building blocks of proteins), urea, sugars, and lactic acid. It is very fond of water (hygroscopic) and absorbs plenty of it, making it a natural humectant (1).
The SC also contains "hydrolytic enzymes" that act as catalysts (substances that activate and speed up chemical reactions). They use water to cleave chemical bonds, splitting large molecules into smaller ones.
The hydrolytic enzymes of the SC clip the protein molecules that retain the dead cells and facilitate the desquamation (flaking) process.
Intercellular Lipid Membranes
There is yet another element in the water-skin balance: the intercellular lipid membranes. These are, as their name implies, (2) a matrix of lipids (oily or waxy substances, like fats, are lipids) that form membranes surround the dead keratin cells of the SC and act as a waterproof barrier against water loss.
Some of the hydrolytic enzymes snip glucosylceramides and phospholipids into fatty molecules that are then used as components for the intracellular lipid membrane (3).
What Causes of Flaky, Dry Skin?
The outermost dead cells of the SC flake away constantly; these tiny cells are invisible to the naked eye, however under certain circumstances abnormal desquamation can occur, causing "Flaky skin" or what is usually called "Dry" skin.
Dry skin causes the dead cells to clump into visible scales and roughens the surface of the skin, altering its appearance.
Many mechanisms can cause Dry of Flaky skin, such as (1)(2):
- Harsh surfactants in soaps. Surfactants are chemicals used to blend fatty and water-based ingredients. They can inactivate the hydrolytic enzymes or leach proteins from the skin surface disturbing the natural skin scaling process.
- "Winter dryness" (known as Winter Xerosis -from the Greek word "xeros" = dryness). The dry and cold winter air reduces the water content in the SC provoking extra flaking.
- Aged skin (4) has slow recovery after wounds and also exhibits a decrease in the production of lipids (fatty substances, particularly cholesterol) which diminishes the skin's barrier properties.
How do I rehydrate my dry skin?
Dry Skin Remedies
The usual treatment for dry skin is to use "moisturizers". These are products that are applied to the skin and add water to it, or help the skin to retain water.
Lotions and creams based on propylene glycol, urea, glycerin, some hydroxy acids such as lactic acid are all "Water Holding" products or humectants.
Others, such as petrolatum form a barrier on the skin that retains water inside the SC (the cream forms an additional barrier that reduces the TEWL (water loss) (1).
Cream moisturizers are only "skin deep"
The moisturizing effect of these humectant lotions is superficial. At a depth of 1⁄10 inches (2.5 mm) no water content changes are observed (5). And this answers the frequently asked question "why is my skin so dry even when I moisturize?"
Fact or Fiction? Can dry skin be caused by not drinking enough water?
Hydrate from the inside out?
Another option is to follow what many beauty magazines and websites suggest: increase the amount of water that you drink to improve skin hydration.
There are two schools of thought about this claim:
Some think it is a myth
This is what Akdeniz (2018) (6) studied, concluding that: "Additional dietary water intake may increase stratum corneum hydration. The underlying biological mechanism for this possible relationship is unknown. Whether this association also exists in aged subjects is unclear. Research is needed to answer the question whether increased fluid intake decreases signs of dry skin."
Akdeniz found that "overall the evidence is weak" (linking water to moisturized skin) but that subjects who drank little water before the study had a "Slight increase" in hydration after increasing their water intake.
Wolf (2010) (7) looked into the effect of drinking six to eight glasses of water per day to keep the skin hydrated and "found no scientific proof for this recommendation" and hinted that "it is all a myth."
Negoianu and Goldfarb (2008) (8) agreed: " it is not clear what benefit drinking extra water has for skin."
Should I drink 8 glasses of water a day?
Conventional wisdom has it that you must drink eight-glasses-of-water-per-day (also known as the "8x8" rule) to keep hydrated. That is eight 8-oz glasses of water. This is a myth that has no scientific basis.
Others believe internal hydration is good for the skin
Below we list some studies that agree with the notion that hydration (by drinking water) is beneficial for the skin:
Wipke-Tevis (2007) (9) found that drinking a pint of water (500 ml) increased the capillary blood flow in the skin in healthy adults. They reasoned that being under-hydrated reduced the amount of oxygen in the subcutaneous tissue which in turn hindered wound healing and increased the risk of infection.
However, the significance or interpretation of how a higher blood flow may impact skin-health is unclear.
Mac-Mary (2006) (10) studied 80 women and men with an average age of 56, who drank extra mineral water every day. The study found "Improvements of softness, smoothness and skin-moisturising effect... suggest[ing] that natural mineral water supplementation may be used in order to improve the hydration of skin dryness."
Williams (2007) (11) studied a group of 86 subjects who drank 2.25 liters of water a day for 4 weeks. They were subdivided into a group drinking tap water and another drinking mineral water. Those who drank the additional mineral water showed a drop in skin density, which is associated with higher moisture retention.
Those who drank tap water, on the other hand, suffered an increase in their skin density (meaning less moisture retention).
Skin thickness increased in the mineral water group and decreased in the tap water group. Skin thickness (thickening of the SC) is believed to be the consequence of water uptake by the cells of the epidermis, and water diffusion causes a swelling or physical expansion: thickening, which theoretically should make wrinkles shallower (12).
However, neither group (tap or mineral water) showed improved "Skin morphology". This means that regardless of the type of water they drank, their skins' wrinkles, scales, or smoothness did not improve.
Tap water vs. Bottled water
There is some public distrust towards tap water which makes people choose bottled water (some of which is tap water too!). But what are the real pros and cons of tap and bottled water? Here we look into some scientific studies on the health and environmental impact of both types of water.
Palma (2015) (13) studied 29 young women (average age 24.5) that were divided into two groups. One (Group 1) that consumed less than 3.2 liters of water a day, the other group (Group 2) drank more than 3.2 liters daily. Both groups then added an extra 2 liters of water to their daily intake for one month.
Over 57% of both groups' water intake was derived from water included in food, juices, and soup. The rest came from drinking other beverages, including water.
The study found:
- No changes in the epidermal barrier and TEWL (transepidermal water loss). In other words, water lost through the skin remained constant for both groups.
- Superficial and deep hydration improved "dramatically" in both groups.
- Group 1, with an initial lower water intake, had the greatest changes.
- Those subjects with dry skin improved significantly.
- "Increasing the dietary water intake would affect the skin the same way as a topical moisturizer."
The study concluded that "these results seem to confirm that higher water inputs in one's regular diet might positively impact normal skin physiology, as expressed by its hydration and biomechanical behavior, and in particular in those individuals with lower daily water consumptions."
So, drinking water might "cure" your dry skin. But, how much water should you drink for dry skin? and How long does it take to hydrate your skin by drinking water?
Palma's study lasted for one month, so you could expect results in that time. The quantity was on average 5.2 liters of water, which is equivalent to almost 11 pints of total intake, including the water contained in solid food.
Skin complexion and a healthy lifestyle
The studies that confirm the positive effect of additional water intake show a greater impact on those who are under-hydrated. This may suggest that adopting a healthier lifestyle can improve skin complexion.
Castillo (2017) (14) analyzed the relationship between healthier dietary habits and skin complexion contemplating other factors apart from water and found that:
- Fruit, vegetable, and yogurt consumption were correlated to skin type (improving it)
- Alcohol intake also correlated (having a negative effect).
- Healthy habits plus water intake also improved skin complexion.
- No correlation between acne and water intake.
Castillo reported that those who drank more water "had healthier habits overall, including exercising and consuming fruits, vegetables, and yogurt, which implies that further assessment is needed to determine which of these factors impact skin appearance and satisfaction."
Water applied directly to the skin
The skin readily absorbs water as you can notice when you shower or take a bath, this effect moisturizes the skin, but it can have side effects if overdone.
According to recent research into handwashing and skin damage during the covid-19 pandemic by Beiu et al. (2020) (15) "Prolonged skin exposure to water and humid environment: It creates extensive swelling of stratum corneum (the skin's outermost layer) and disruption in the ultrastructure of intercellular lipids, and heightens the skin’s permeability and sensitivity to physical or chemical irritants".
In the end, Castillo's outcome may be the real point behind a good skin complexion: a healthy lifestyle with a balanced diet and an adequate water intake may all contribute towards better skin.
References and Further Reading
(1) Kathi C. Madison et al. (2003). Barrier Function of the Skin: "La Raison d'Être" of the Epidermis. Journal of Investigative Dermatology August 2003 Volume 121, Issue 2, Pages 231-241. DOI: https://doi.org/10.1046/j.1523-1747.2003.12359.x
(2) Das C, Olmsted PD, (2016). The physics of stratum corneum lipid membranes. Philos Trans A Math Phys Eng Sci. 2016 Jul 28;374(2072). pii: 20150126. doi: 10.1098/rsta.2015.0126
(3) Clive Harding (2005). The importance of intrinsic enzyme activity for stratum corneum health. Journal of the American Academy of Dermatology, Volume 52, Issue 3, P41. 100% supported by Unilever Home & Personal Care
(4) Zettersten EM, Ghadially R, Feingold KR, Crumrine D, Elias PM. (1997). Optimal ratios of topical stratum corneum lipids improve barrier recovery in chronologically aged skin. J Am Acad Dermatol. 1997 Sep;37(3 Pt 1):403-8.
(5) Guzman-Alonso M, Cortazar T., (2016). Water content at different skin depths and the influence of moisturizing formulations. H&PC Today - household and Personal Care today, vol. 11(1) Jan/Feb 2016
(6) M. Akdeniz T. Tomova-Simitchieva G. Dobos U. Blume-Peytavi J. Kottner, (2018). Does dietary fluid intake affect skin hydration in healthy humans? A systematic literature review. Skin Research and Technology. Vol 24:3 Aug 2018, 459-465 https://doi.org/10.1111/srt.12454
(7) Wolf R, Wolf D, Rudikoff D, Parish LC, (2010). Nutrition and water: drinking eight glasses of water a day ensures proper skin hydration-myth or reality?. Clin Dermatol. 2010 Jul-Aug;28(4):380-3. doi: 10.1016/j.clindermatol.2010.03.022
(8) Negoianu D, Goldfarb S, (2008). Just add water. J Am Soc Nephrol. 2008;19:1041-1043
(9) Wipke-Tevis DD, Williams DA, (2007). Effect of oral hydration on skin microcirculation in healthy young and midlife and older adults. Wound Repair Regen 15 : 174 -185, 2007 DOI: 10.1111/j.1524-475X.2007.00202.x
(10) Mac-Mary S et al. (2014). Assessment of effects of an additional dietary natural mineral water uptake on skin hydration in healthy subjects by dynamic barrier function measurements and clinic scoring. Skin Res Technol. 2006 Aug;12(3):199-205. DOI: 10.1111/j.0909-752X.2006.00160.x
(11) S. Williams N. Krueger M. Davids D. Kraus M. Kerscher, (2007). Effect of fluid intake on skin physiology: distinct differences between drinking mineral water and tap water. April 2007 International Journal of Cosmetic Science, Vol 29:2 131-138 https://doi.org/10.1111/j.1467-2494.2007.00366.x
(12) Dabrowska AK et al., (2016). In vivo confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment. Biointerphases. 2016 Sep 15;11(3):031015. doi: 10.1116/1.4962547
(13) Lidia Palma et al., (2015). Dietary water affects human skin hydration and biomechanics. Clin Cosmet Investig Dermatol. 2015; 8: 413-421. 2015 Aug 3. doi: 10.2147/CCID.S86822
(14) Castillo V. (2017). Relationship Between Water Consumption and Overall Skin Complexion Satisfaction in Individuals Ages 18-24. Thesis, Texas Christian University
(15) Beiu, Cristina et al. (2020) Frequent Hand Washing for COVID-19 Prevention Can Cause Hand Dermatitis: Management Tips. Cureus vol. 12,4 e7506. 2 Apr. 2020, doi:10.7759/cureus.7506
About this Article
Water and skin complexion, A. Whittall
©2018 Fit-and-Well.com, 11.Oct.2018. Updated. 12.Dec.2020. https://www.fit-and-well.com/wellness/water-and-skin-complexion.html
Tags: dehydration, 8 x 8 rule, hydration, water requirements, daily water intake, skin complexion, fluid Intake, acne, dry skin, flaking skin, humectant, moisturize.
Subject: Fit-and-Well.com. Does a low water intake cause Dry Skin? Can you improve dry skin by drinking more water? Adequate hydration is said to improve skin complexion. What does science have to say about it? How to moisturize and hydrate your dry skin naturally?