Should you avoid SLS in your cosmetics if you have sensitive skin? This question has spurred quite some debates in skintellectual circles recently. The line of debate primarily lies between dermatologists and cosmetic formulators. Dermatologists (including our advisor Dr. Sandy Skotnicki) have been advising for a while to avoid SLS-containing products if you have a sensitive, reactive skin. Cosmetic chemists, on the other hand, insist that products with SLS can be formulated to be non-irritating. Here are our thoughts on the matter.
SLS is the industry standard skin irritant. It is the go-to irritant researchers use as a control group for skin irritation studies. It is also used to evaluate the sensitivity and accuracy of different methods used to detect irritant skin response. For example, in this in-vivo study , different patch test systems were evaluated for detection of irritant skin reaction to water, 0.06% concentration of SLS, and two cosmetic products. The choice of the patch test system mattered: while the first one tested did not show a meaningful difference between the skin reactions to water and 0.06% SLS, the second one detected the stronger reaction to the SLS.
What does it mean for us, consumers? We think that in the case of the SLS debate, it is more prudent to follow the advice of the dermatologists and err on the side of caution - that is avoiding SLS in your products if your skin is sensitive. We have data to confirm that SLS is irritating to the skin even in small concentration, even though not all test methods used can detect it. Besides that, most cosmetic products are not tested using the cumulative irritancy testing - so we are not sure what data do cosmetic formulators have to show that their SLS-containing products are indeed less irritating than, let's say, the 0.06% SLS emulsion used to induce skin irritation in the study cited above.
The diagnosed incidence of cosmetics-related skin reactions in North America has increased by 2.7 times in North America over the decade between 1996 and 2006, finds a study recently published in the Journal of the American Academy of Dermatology. This study did not include irritant and allergic reactions to sunscreens.
In 1996-1998, out of people referred to patch testing, 22% of females and 17% of males had an irritant or allergic reaction to cosmetic ingredients. These numbers more than doubled in 10 years, when 49% of females and 49% of males tested had a positive patch reaction to cosmetic ingredients.
Other data from Europe confirms the trend A Danish study found that contact sensitization to cosmetic allergens doubled from 1990 to 1998. In a 2013 survey, European dermatologists noted a 5-year increase in males reporting sensitive facial skin.
Inulin is a polysaccharide (a big sugar molecule) that is produced by many plants and bacteria. Inulin is widely used in food: it is a sweetener and also is a source of soluble fiber.
Inulin is also considered to be a dietary prebiotic (prebiotics are roughly defined as a food source for beneficial bacteria in our bodies). Inulin passes through most of our digestive system and reaches colon intact (it cannot be digested by our enzymes). Because of this, it is available as a food source to the bacteria in our colon and this is how it supports diversity of gut microflora.
Inulin is one of the most studied prebiotics - when it comes to the ingestible ones. There is no research available that inulin applied to the skin topically can improve or support skin microbiome, even though companies produce and market skincare ingredients with inulin For example, a skincare ingredient Biolin (a combination alpha-glucan-oligosaccaride and inulin on the INCI list) is claimed by its manufacturer to support skin’s microbiome, but the available studies do not include adequate control groups.
Hyaluronic acid does not cause sun sensitivity. The reason you do not need to worry about additional sun avoidance when using hyaluronic acid is that it is not very acidic. The pH of solutions of hyaluronic acid is close to the natural pH of the skin. The form that is most often used in skincare is actually not an acid at all - it is a salt sodium hyaluronate. Either form of hyaluronic acid does not exfoliate the skin and does not make it more vulnerable towards the sun.
This means that you can safely apply products with hyaluronic acid under your sunscreen during the day. In fact, it is a great way to incorporate hyaluronic acid into your routine: apply a hyaluronic acid serum on damp skin in the morning (go for the high molecular weight one, listed as “hyaluronic acid” in the ingredient list if your skin is prone to sensitivity), and seal it in with the sunscreen. Do not use hyaluronic acid without following up with a moisturizer, especially in a dry climate - otherwise it can “pull” the water from your skin leaving it dryer.
Short answer is: yes, it is plausible. If your skin is reactive and sensitive, prone to redness and small inflamed spots, a product with hyaluronic acid might be the issue.
Not all hyaluronic acid is created equal. We have two types of hyaluronic acid present in our skin naturally: a high molecular weight (big molecules) and low molecular weight (small molecules) hyaluronic acid.
The big molecules of hyaluronic acid (HA) are part of the top layer of our skin where they help our skin create and maintain an effective protective barrier between the deeper layers of our skin and the external environment. They help attract water to the upper layer of the skin keeping it supple, flexible and what skincare marketers usually describe as radiant. Applying high molecular weight HA to the skin topically can support skin barrier function through attracting moisture - as long as the application is combined with an emollient (for example, an oil or silicone) to “seal it in” (if HA is applied to the skin on its own in a dry environment, it can pull water out of the skin leaving it drier).
Salicylic acid (sometimes referred to as BHA) does not increase skin's sensitivity towards the sun. You still should be using a sunscreen most day of the year, whether or not you are using a salicylic acid, but no extra precautions are needed for this exfoliating ingredient. This sets salicylic acid apart from another popular category of exfoliating acids - AHAs, and glycolic acid in particular that does increase skin's sensitivity to the UV light. This is why it is best to use glycolic acid in the evening and avoid sun exposure for a few days altogether after using glycolic acid peels in concentrations above 5%.
There is no harm in using salicylic acid in the morning even if you plan going outside during the day. Just make sure to use a sunscreen as usual, and do not overdo it with the exfoliation as thinner top layer of the skin offers less physical barrier for the sun rays.
Here is an interesting piece of skincare trivia: salicylic acid can actually have a small photo protective effect on the skin. Two clinical studies have showed that salicylic acid, when applied shortly before exposure to UV radiation, decreased the sunburn. It is important to emphasize though that in these experiments, a relatively high concentration of salicylic acid was applied in large quantities shortly before the UV exposure. In other words, salicylic acid was still on the surface of the skin during the sunlight exposure and was able to act as a sunscreen by absorbing the UV energy directly. You can not use salicylic acid as a sunscreen though - to get any practical sun protection, you would need to use a concentration way above 2% that is commonly used in cosmetics, and this concentration would cause too much exfoliation and irritation for frequent use.
Centella Asiatica (also called Gotu Kola) is one of the most popular plant extracts in skincare products in the recent years. Products with Centella Asiatica have even received a designated prefix - they are called “cica-creams”, “cica-balms”, and “cica-serums”. They are particularly marketed for sensitive and reactive skin, and this is one of the relatively rare cases when a skincare hype has a ground. Centella Asiatica can indeed be helpful for sensitive skin. Gotu Kola could be considered for a supportive care regimen for people with eczema, rosacea and psoriasis. At the same time, there are two issues you might want to consider before buying one of those trendy cica-products. The first one is that Centella Asiatica extract can itself cause a skin irritation. The second issue is of an environmental nature: the current way of harvesting Gotu Kola is not sustainable.
Keep reading for a more detailed overview.
What is it?
The WIMJ Irritancy score gives you an estimate of how likely a product is to irritate the skin. The irritation risk estimate is based on the clinical and research data available. The “fire” icon indicator tells you if a product has a low (green), medium (yellow), or high (red) irritancy risk.
If the WIMJ algorithm flags a product with a medium or high skin irritation risk, it does not mean that the product will certainly cause a problem. Rather, it suggests that the chance of irritation is higher for this product compared to the low irritancy ones. By the same token, a product with low irritation risk can still cause a reaction, especially if you have a rare sensitivity or developed an allergy to a particular ingredient. It is always best to review the full ingredient list and patch test new products before using them.
The WIMJ Efficacy score tells you if a product can deliver on its promises. The closer the score is to 100, the higher the chances that it will have the skin benefits that it claims, and the better is the overall quality of its formula.
WIMJ Efficacy score depends on the explicit claims that the product makes. For example, if a moisturizer claims anti-aging benefits, our algorithm evaluates its formula’s ability to deliver both on anti-aging and moisturization.
Keep in mind that the WIMJ algorithm evaluates only the product formula, it does not test the product in terms of sensory feel and might not take into account all the ways in which ingredients can work together. We advise that you use our Efficacy score as an indication of whether the product can possibly deliver on its promises, and not as a guarantee that it will.