We’ve all heard that night creams work better because your skin absorbs ingredients while you sleep. Is this true? Tune into to this week’s show to find out. Also, Randy and I talk about how beauty companies cut costs on cosmetic formulas.
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Question of the week: Do night creams work better at night?
Christine says…I’ve read that night creams are supposed to work better because the skin heats up at night so the ingredients penetrate more deeply. Is this true?
What happens to your skin at night?
First of all, there doesn’t seem to be any question that sleep is good for skin. Lack of sleep can actually impair the barrier function of skin which means TEWL is increased. In other words – not getting enough sleep literally dries out your skin. For example, one study found that “Sleep deprivation also decreased skin barrier function recovery and increased plasma interleukin-1beta, tumor necrosis factor-alpha, and natural killer cell activity.” So dryness, psoriasis, eczema, and other types of dermatitis can be triggered by lack of sleep.
The hypothesis which explains this is that sleep gives the body time to repair itself. During the day the sympathetic nervous system is in control and it keeps blood flow near the core of the body. At night the parasympathetic system takes over and it shifts blood flow to the extremities. Theoretically, this is when the skin builds more collagen. In addition, the kidneys are more active during the parasympathetic phase and they are able to drain excess fluid that can create puffy eyes. So, sleep is good for skin but does it actually cause the skin to “heat up” as Christine mentioned?
Ref: Stress-induced changes in skin barrier function in healthy women. J Invest Dermatol. 2001 Aug;117(2):309-17. http://www.ncbi.nlm.nih.gov/pubmed/11511309
Does the skin heat up at night?
The answer is yes, at least for part of the night. We found a study which measured blood flow and skin temperature during sleep. By the way the technical term for this is nocturnal subcutaneous blood flow. The researchers found that after about an hour of sleep blood flow does increase to the skin (at least to the legs which is what they measured in the study.)
They also found that with this increasing blood flow comes a statistically significant increase in temperature which makes sense since the body cools itself by vasodilation. Interestingly this effect lasts for about two hours before returning to normal levels. So if you’re not sleeping for at least three hours total it doesn’t seem to make much difference.
This all means that Christine is correct – it does appear that as you sleep subcutaneous blood flow and skin temperature both increase. But, what impact does this have on the absorption of cosmetic ingredients through your skin?
Do increased temperature and blood flow lead to increased ingredient absorption?
There are two parts to this answer: first there’s the question of how well ingredients diffuse through the outer layers of skin to get to the bloodstream. Second there’s the question of how well the ingredients are absorbed into the blood stream once they pass through the skin.
As far as we can tell, no one has done a study correlating blood flow and the absorption of cosmetic ingredients. However, there’s plenty of research on the factors that affect absorption of drugs that are applied topically to the skin. For example, one study found that physical exercise increased plasma concentrations of nicotine during treatment with a nicotine patch. The researchers attributed this increase in absorption to “an exercise-induced increase in blood flow in the patch area.” http://www.ncbi.nlm.nih.gov/pubmed/7654487
So, yes, blood flow can increase absorption at least of drug ingredients that are designed specifically to penetrate all the way through skin. We could find no evidence that it would increase penetration of ingredients that are NOT prone to penetrate in the first place.
What about heat? Does that increase absorption? One study measured the effect of applying heat at the site of subcutaneously injected insulin. Since it was injected it bypassed the outer layers of skin. The results showed that increasing skin temperature did NOT cause the insulin to perfuse through the remaining tissue to any greater extent. And, considering that this was externally applied heat which was greater than what you’d experience from a modest increase in blood flow, it seems very unlikely that a small increase in skin temperature due to blood flow would impact ingredient penetration. http://www.ncbi.nlm.nih.gov/pubmed/22162782
Do night creams provide ANY special benefit?
We haven’t been able to find convincing evidence to indicate that night creams are better because your skin absorbs ingredients better as you sleep. But is there ANY benefit to applying products at night? Yes, there are a couple of reasons why you might want to use a night cream.
First, some cosmetic ingredients make skin more sensitive to sunlight which means you could experience increased irritation or photo damage if you’re wearing these ingredients while in the sun. If you wear a sunscreen this may not be an issue but you can also get around that problem by applying these ingredients at night. Here are some examples of ingredients that can make skin more sensitive to sunlight:
- AHAs – like lactic acid or glycolic acid.
- Benzoyl Peroxide – the antiacne agent.
- BHAs – or Beta Hydroxy Acids like salicylc acid.
- Hydroquinone – which is used for skin whitening
- Retinol – the popular anti-aging ingredient.
- Some natural ingredients – like citrus oils, peppermint oils, lavender, etc may increase photosensitivity.
Second, some ingredients are just too aesthetically unpleasant to wear during the day. For example, you wouldn’t want to walk around with a heavy, greasy moisturizer on your face but you might not mind sleeping with a moisturizing mask on.
Don’t just take our word for this
Finally, don’t just take our word for this. Paula Begoun, the Cosmetic Cop also says night creams are mostly BS. She says:
“The ONLY difference between a daytime and nighttime moisturizer is that the daytime version should offer sun protection.”
“…cosmetics salespeople say is that the skin needs different ingredients at night than during the day…If that’s the case there isn’t a shred of research or a list anywhere of what those ingredients should be. Skin is repairing itself and producing skin cells every nanosecond of the day, and night.”
“Regardless of the time of day, your skin needs all the current state-of-the-art ingredients it can get. Saving these ingredients only for nighttime use is cheating your skin of the benefits it could be gaining during daylight hours, too!”
The Beauty Brains bottom line
Yes there are some changes that occur within your skin at night and sleep is certainly beneficial to skin. However, that doesn’t mean that night creams provide any special functionality. In general it’s more about avoiding things that you wouldn’t use in the sun rather than adding things that work better at night.
Buy your copy of It’s OK to Have Lead in Your Lipstick to learn more about:
- Clever lies that the beauty companies tell you.
- The straight scoop of which beauty myths are true and which are just urban legends.
- Which ingredients are really scary and which ones are just scaremongering by the media to incite an irrational fear of chemicals.
- How to tell the difference between the products that are really green and the ones that are just trying to get more of your hard earned money by labeling them “natural” or “organic.
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