Does using an oily sunscreen lower the SPF?
Emma asks on Gmail…I don’t like the oily skin I get from using sunscreen so I wipe off the excess with an oil absorbent sheet. Does this reduce the SPF of the sunscreen?
Yes, slathering sunscreen on your face will reduce UV protection, to some extent. That happens for two reasons:
First, most UV absorbers are not water soluble so they are dissolved or dispersed in the oil phase. That means a higher percentage of the active ingredient is in the oil you’re removing. And less of that active ingredient means less sun protection.
Second, good sun protection depends on having a thick, even film of sunscreen on your skin. In fact, dermatologists specifically mention sunscreen wipes as one of the main reasons for reapplying.
Apparently this is a good read because I found a paper titled “Effect of Film Impairment on Sunscreen Performance” in the Journal of Pharmaceutical Science. Researchers tested how effective sunscreen films were and found that “The uneven distribution of sunscreen films on the skin … accounts for the large difference between the efficacy predicted arbitrarily and that observed clinically.” In other words, no matter how good the sunscreen is, if the film isn’t the same it won’t work well.
The bottom line is that wiping off excess oil is one of the ways to disrupt the film so if you want good sun protection, you shouldn’t do it.
Is it safe to use fabric softener on hair?
Chloe asks…is it safe to use fabric softener on your hair?
I think this qualifies as one of those DIY beauty hacks we’ve been talking about lately. I’m not sure WHY you would want to do this – to save money? For a better situation? Regardless of your thinking here are 3 reasons this is not a good idea:
1. Be careful to build
Fabric softeners have a stronger charge than most hair conditioners. That means they can stick to a fabric that provides long-lasting softness. This is a good thing when it comes to your washing up rather than normal. However if your hair is curly, frequent use of a soft cloth can cause dreaded build-up.
2. You want the best for your hair
The ingredients are made to stick to the fabric but can also stick to your hair after washing which is why they work so well. But that’s where the similarities end. A good conditioner will add some sort of shine-enhancing agent to your hair, for example silicone. You won’t find this fabric softener as “shininess” is generally not desirable in clothing. The types of quats used in hair cosmetics are fine-tuned to deliver the best possible beauty experience. Ingredients that are good at softening fabric may leave here feeling heavy and limp with a noticeable waxy coating. Fabric softeners are also scented and you may find yourself smelling like Downey or Snuggles compared to your usual salon brand.
3. Skin safety
Of course the main concern is safety. Cosmetics (despite what some people may tell you otherwise) are formulated and tested to ensure they are safe for prolonged contact with the skin. There are many regulations that govern what can and cannot be used in cosmetics.
Not surprisingly, the laws governing fabric softeners are different than those governing cosmetics. That’s not to say fabric softeners are necessarily harmful, but they’re not meant to be used in direct, long-term, skin contact. Let’s take a look at the ingredients in Downy which is probably the most popular brand.
DEEDMAC: The main ingredient, which provides the condition, is diethyl ester dimethyl ammonium chloride (or DEEDMAC). The good news is that studies have found that this is NOT a warning sign for the skin. Similar and similar ingredients are used in cosmetics.
Formic acid: which is a skin irritant and can cause allergic reactions. It is not used in cosmetics.
Benzisothiazolinone: The preservative is a cousin of MI and is known to cause allergic reactions in some people. One research paper put the odds of people disagreeing with this somewhere between 2% and 23%. This is not used for cosmetics.
Colorant: Liquitint® Sky Blue Dye is a color molecule linked to several polymers. It’s not approved for cosmetics but it’s necessary here to prevent your white towels from getting dirty. It showed that the common soluble blue dye is highly polluting. This color is NOT allowed in makeup.
Finally, the word about pH is 4 which is typical for a cationic conditioning product like this. That’s because with a slightly acidic pH the conditioner has a positive charge which means it will stick to areas of hair damage or negatively charged fabric.
Bottom line, why risk staining your hair and damaging your skin with a product not designed or tested for personal care use?
What is a non-irritating alternative to shaving cream?
Peter asks…All the regular shaving creams/gels I’ve tested have a pH value between 8.5 and 10 and use ingredients like sles or cocamide mea these products leave my skin itchy, red and dry. The dermatologist recommended that instead of washing the face, apply a regular moisturizing cream and shave with it. I’ve tried it with basic cleansers and moisturizers, and my skin is less dry, but it doesn’t provide the same barrier/smoothness as most times. So I’m wondering if it’s wise to replace your shaving cream with an emollient moisturizer, and what ingredients have a smooth feel and provide a barrier to the skin so the blade can glide easily over your skin?
(Most) shaving creams are real soaps meaning they are made from saponified oils (usually stearic acid) and some type of alkaline agent like triethanolamine (hence the high pH.)
The advantage of this type of formula is that it does a good job of moisturizing the hair and provides a lot of moisturizing smoothness. The downside is that it can offend some people. As you pointed out, shaving with an emollient cream is a good idea if you have sensitive skin but, depending on the formula, it may not provide the same level of smoothness.
Unfortunately, it’s not easy to tell which ingredients have a smooth feel because it depends on how those ingredients are made into the finished product. For example, many silicones provide a lot of smoothness but if they are made from creams with cetyl or stearyl alcohols then the finished product can feel draggy.
This is one of those situations where you’ll have to use trial and error to find a refreshing cream that gives you the right level of smoothness for your personal taste. Having said all that, I have one off-the-wall suggestion for you. You might try one of those anti-chafing bikini gel products like the Monistat product. It’s almost pure silicone so you like the way it feels. (But surely it won’t wet the beard hair so maybe it will be harder to cut? I don’t know, just a guess.
What is working with ionic hair dryers?
Marta says… How do ionic hair dryers work? I read one website that says it makes the H2O molecules break up into smaller particles that evaporate faster. Another website says that the ions themselves provide some benefit to your hair. Can you explain it?
I can’t explain it because it’s not true! We’ve heard this claim for years but I’ve seen little evidence to show that blowing hot ionized air through your hair provides any benefit.
Don’t get me wrong – ions have their place in hair conditioning. Specifically, that’s how certain types of conditioners can stay on your hair after you wash it. One part of the molecule has a positive charge and sticks to the less charged areas of your hair which is where the damage is the most. So one part is the “anchor” but the other part of the molecule is a long chain of carbon atoms. This “oily” part coats the hair like a thin coat of oil. When you blow ionized air through your hair you just get water ions that don’t have the same properties.
Want to learn more about beauty supplements? Visit Makeup Design.
We are working on a project with another chemist, Paige DeGarmo, who runs the website www.cosmeticcomposition.com. She does a great job of explaining the science behind beauty products. If you like Beauty Brains you will also enjoy her website. Here are a few of my favorite articles:
What is Micellar Water?
How does product formulation affect skin penetration?
What is the difference between antiperspirant and deodorant?
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Teelovespods said… I listen to this when I do my morning routine. I enjoy the honest explanations, witty sarcasm, and concise information.
Anonymous59724 says… This is useful information, presented in an engaging way, really accessible to those with no knowledge of high school chemistry. My only complaint is that it’s slow going, and that occasionally the moderators talk about beauty stories that aren’t very interesting.
