Does Drinking Water Help Dry Skin? Yes

What is dry skin?

You may experience dry skin or dehydrated skin during the cold, winter months.

What is normal skin hydration?

Water is essential for the normal functioning of your skin. 

The water content of skin is remarkably high - the epidermis (the outer skin layer) contains more than 70% water, while its outermost layer, the stratum corneum has been shown to contain ~15 - 25% water (Warner et al, 1988; Caspers et al, 2001; Caspers et al, 2003).

1. It maintains plasticity of the skin, protecting it from damage.
2. It contributes to optimum stratum corneum barrier function.
3. It allows hydrolytic enzymes to function in the process of desquamation.

When the water content of the stratum corneum falls below 10%, scaling on the skin surface becomes visible (Rycroft, 1985).

However, it is not as simple as just drinking water, or treating your skin with water or a moisturizer.

The retention of water in the skin is dependent on:

1. Natural moisturizing factors (NMFs) and other humectants (such as glycerol and hyaluronic acid) to attract and hold onto moisture.
2. Intercellular lipids (fats) that form a barrier to prevent transepidermal water loss (TEWL) (Verdier-Sévrain et al, 2007). 

Water and skin cell turnover

Daily insults from the environment, such as low humidity, surfactants, wind, and sun, can lower the skin's water content, causing improper desquamation and the appearance of dry, flaky skin (Verdier-Sévrain et al, 2007).

Desquamation is the natural process of shedding skin cells.

New skin cells are formed at the base layer of the skin, and they differentiate and migrate towards the skin surface, in a process that takes approximately 4 weeks. Nearly a billion cells are lost each day from the surface of adult skin (Milstone et al, 2004). 

One of the critical functions of water in the skin is to participate in hydrolytic enzymatic processes required for normal desquamation. 

In other words - water is necessary for the enzymes to function properly. 

If the skin water content falls below a critical level, the enzymatic function required for normal desquamation is impaired, leading to skin cells sticking and building up on the skin surface (Verdier-Sévrain et al, 2007). 

These changes lead to the visible appearance of dryness, roughness, scaling, and flaking (Verdier-Sévrain et al, 2007).

Many adults are inadequately hydrated

Water is involved in virtually all bodily functions.

Thus, ensuring that the body has enough water to maintain proper function is important for health. 

The primary indicator of hydration status is plasma or serum osmolality (National Academies of Sciences, Engineering, and Medicine, 2005).

According to the analysis of combined urine osmolality data from the NHANES 2009–2010 and 2011–2012 surveys, about 1/3 (32.6%) of adults (ages 18–64 years old) are inadequately hydrated (Chang et al, 2016).

The importance of adequate fluid intake is also believed to maintain an adequate skin hydration (Hurlow et al, 2011).

For instance, drinking six to eight glasses of water per day is recommended to help proper skin hydration (Wolf et al, 2010).

Drinking water can increase water in the dermis

It is well-known that increased fluid intake increases the water content in the dermis layer of the skin, because the water accumulates in this layer (Eisenbeiss et al, 2001).

An increased water content in the dermis may also increase the water content in the epidermis (Brazzelli et al, 1994).

Can drinking water help your dry skin?

In 2018, Akdeniz and colleagues published a review paper analyzing 6 studies to determine whether fluid intake affects skin hydration and skin barrier function.

In an observational study there was a weak positive association between fluid intake and stratum corneum hydration (Boelsma et al, 2003).

Drinking an additional 2 L of daily water over 30 days showed an increase in both stratum corneum hydration and “deep” skin hydration, particularly when the individual’s regular diet included low amounts of water (Palma et al, 2012; Palma et al, 2015a; Palma et al, 2015b). 

Another experimental study reported a slight increase in stratum corneum hydration after an additional dietary water intake of 1 L per day for a period of 42 days (Mac-Mary et al, 2006). 

Overall, the evidence is weak in terms of quantity and methodological quality.

However, despite the limitations, a slight increase in stratum corneum and “deep” skin hydration was observed after additional water intake, particularly in individuals with lower prior water consumption (reviewed by Akdeniz et al, 2018).

There was also a reduction of clinical signs of dryness and roughness. Furthermore, the extensibility and elasticity of the skin increased slightly.

Unclear associations were shown between water intake and transepidermal water loss, sebum content, and skin surface pH (reviewed by Akdeniz et al, 2018).

Results showed no associations between transepidermal water loss at any skin area and an additional intake of mineral water of 1 L over 42 days (Mac-Mary et al, 2006) or 2 L over 30 days (Palma et al, 2012; Palma et al, 2015a; Palma et al, 2015b).   

How much water should you drink for hydrated skin?

How much water you need varies from person to person.

For adults, the general recommendation from The U.S. National Academies of Sciences, Engineering, and Medicine is about:

• 11.5 cups (2.7 liters) a day for women
• 15.5 cups (3.7 liters) a day for men

This includes fluids from water, beverages like teas and juice, and from food.

You get an average of 19% of your water from the foods you eat.

For hydrated skin, it is best to aim for 6 - 8 glasses of water or other fluids per day, as is recommended for general health.