What Is Thermal Water?
You may have come across thermal water before, through brands such as La Roche-Posay, Avène, and Uriage. Thermal water is sold as a facial mist that provides the skin with a source of minerals, sets makeup, and helps other skincare products spread easily and evenly across the skin. It may also support your skin’s natural moisturizing factors which help to keep the skin hydrated and well protected.
Thermal water is collected from hot springs. Hot springs are water that has been heated deep underground where geothermal activity is high. The water then rises to the surface where we are able to access the water in the form of hot springs. You may be familiar with the hot springs in the mountains of Japan. Thermal water is essentially just water from specific hot springs, used just for this purpose, rather than for bathing or tourism.
There is one key difference between surface water, the water we usually drink and thermal water and that is the presence of minerals. As the water passes through rocks and soil when rising from the deep underground springs where it is heated it collects minerals. These minerals dissolve into the water and are present when the water arrives at the hot springs on the surface.
The type and concentration of minerals will be specific to different hot springs. For example, one hot spring will have a high content of calcium than others. This makes the different thermal water brands on the market, all slightly different. The minerals that are commonly found in thermal water are similar to your skin’s natural moisturizing factors or NMF. These minerals include chlorides, sodium, potassium, calcium, and magnesium.
the good: Thermal water provides the skin with minerals, helps to cool the skin, help your other products spread readily, and may support your natural moisturizing factors.
the not so good: There isn’t a lot of research to suggest that thermal water has a significant benefit to the skin.
Who is it for? All skin types except those that have an identified allergy to it.
Synergetic ingredients: Works well with most ingredients.
Keep an eye on: Keep an eye out for more research into thermal water and its benefits.
What Are The Benefits of Thermal Water?
There isn’t a whole lot of peer-reviewed research on the benefits of thermal water to the skin. Most of the studies that are available are conducted by the research teams at the companies that have thermal water products. While its important to keep in mind that this may present some bias in the types of benefits each brand looks at the studies can still be evaluated. It is often hard to find independent research on ingredients that aren’t widely used across the industry.
Most of the research that has been conducted has been on the Avène and La Roche-Posay thermal waters. This means that most of the research has been conducted on their thermal waters and the specific mineral concentrations that are present in their product. This doesn’t mean that other thermal waters wouldn’t produce the same benefits as the Avène and La Roche-Posay just that these two are the most well-reserached.
Natural Moisturizing Factors
One of the potential benefits of the minerals that are contained in thermal water is that they may support the skin’s natural moisturizing factors. Natural moisturizing factors are minerals, amino acids, urea, fatty acids, ceramides, sugars, and hyaluronic acid, which form a layer or barrier on the surface of the skin. The natural moisturizing factors as their name would suggest help to support the skin’s hydration. Many of the minerals that are present in the skin’s natural moisturizing factors are present in thermal water.
There has been limited research as to whether using thermal water would support the skin’s natural moisturizing factors. However, there has been research that links the use of thermal water with the improvement of the hydrated appearance of the skin
One of the benefits of thermal water that may not seem as obvious is that it can help you to apply your skincare. The thermal water, when applied to the skin before the rest of your skincare routine can prevent your other products from catching on dry patches of skin, allowing for even and smooth application of your skincare.
The main benefit of thermal water is considered to be its soothing or calming benefits to the skin. This is why it is often recommended for inflammatory skin conditions such as eczema, psoriasis and ichthyosis.
There are a few studies that support this claim. In a study conducted by La Roche-Posay, thermal water reduced the irritation caused by sodium lauryl sulfate on the skin, a known irritant.
Another study conducted by Avène found that the use of thermal water reduced the severity of eczema when added to a hydrating cream. The same study also found that the addition of thermal water to the cream also decrease the amount of inflammation-causing bacteria on the affected skin.
La Roche-Posay, Uriage and Avène thermal waters have also presented evidence that they may help to protect the skin’s cells from UV damage, in particular UVB exposure. A La Roche-Posay thermal water-based cream moisturizer also produced evidence that it reduced the formation of sunburn cells on the skin of the human participants.
The explanation of this benefit may be found in the zinc, selenium, and copper minerals that are present in the thermal water. These minerals help to absorb UV light and protect the skin against free radicals.
This doesn’t mean that you can ditch your SPF just yet but it may help to further protect the skin from UV damage.
What Are the Differences Between the Thermal Water Brands on the Market?
The main difference between the brands is the amount and type of minerals that the water contains. For example, in a study conducted on the mineral concentrations of the top three thermal water brands, Uriage had the highest concentration of minerals. The benefits may also depend on the ratio of specific minerals, for instance, the 2:1 ratio between calcium and magnesium in the Avène thermal water is something they present as unique.
Interestingly, the higher mineral content of thermal water does not equate with benefits. In fact, lower mineral contents, such as Avène, may be better for improving the appearance of the skin. Keep in mind that all this research is being conducted by the respective parent companies and while the science may still stand specific claims may be investigated to suit the companies’ needs.
Is Thermal Water Safe?
Thermal water is considered to be safe for use as a skincare or cosmetic product. While it is just mostly water, some thermal waters with higher concentrations of minerals may be more irritating than others. If you have sensitive or irritated skin it may be best to use a thermal water with a lower mineral content.
Cacciapuoti S, Luciano MA, Megna M, et al. The Role of Thermal Water in Chronic Skin Diseases Management: A Review of the Literature. J Clin Med. 2020;9(9):3047. Published 2020 Sep 22.
I Bacle, S Meges, C Lauze, P Macleod & P Dupuy, Sensory analysis of four medical spa spring waters containing various mineral concentrations, Int J Dermatol 1999, 38, 784–6.