like those used by CosDNA? Have these been discredited, or is there something to them? I see lots of people attempting to single out and eliminate specific acne “triggers” — i.e. specific troubling ingredients — and I’m wondering if so doing is a fool’s errand? What do you think?

Hello!

CosDNA doesn’t list their sources (to my knowledge), but comedogenicity data is generally performed on rabbits, or rabbit ears specifically.

A high % (50% to 100%) of the ingredient is placed on the ear for a period of time and then monitored for comedones. Sometimes the ingredient is injected under the skin.

Researchers started coming to conclusions that moved them away from using these 1 ingredient animal results.

Firstly, while rabbit ears easily form comedones, they don’t correlate to human skin.

And secondly, using 1 ingredient in a high concentration doesn’t reflect its use in a consumer product.

Human sebum, for example, is very comedogenic. But it doesn’t cause problems for everyone.

My personal opinion is that the melting point of an oil or wax is more indicative of whether it will cause clogs or not. If your skin is warm enough to melt it, it’ll remain in a more fluid state, and less likely to clog pores.

It gets more complicated when you consider irritancy of an ingredient as well. While an ingredient might not be pore clogging, if it can cause enough irritation it may cause already formed microcomedones or comedones to erupt into inflammatory acne. This sometimes gets characterized as “purging”, especially common with prescription retinoids and chemical peels.

Hope that helps!

"Dear Mr. Ko, Could you offer your professional opinion of comedogenic scales" on KindofStephen.

What if they’re combined in a single product? Does niacinamide reduce to niacin and become useless? I’m using something like this: Aqua(Water), Mandelic Acid(10%[?]), Lactobionic Acid, Niacinamide, Sodium Hyaluronate, Allantoin, Hydroxyethylcellulose, Polysorbate 20, Ethylhexylglycerin, Phenoxyethanol, Parfum(Fragrance), Butylphenyl Methylpropional, Hydroxycitronellal, Limonene, Linalool. I’m not flushing [maybe shizo].

Niacin isn’t useless, it just causes flushing for some people – that’s all.

The amount of niacinamide hydrolysis depends on the pH of the product, how long it’s been stored for, and at what temperature. It’s also possible that there isn’t much niacinamide in the product. Unless it states the amount on the package there’s no way to know, it could be 0.1% or 4%.

If you’re not experiencing flushing and enjoy using the product – then keep using it!

Hope that helps

"Hi, I have some further doubts about niacinamide and acids." on KindofStephen.

Previous research has shown that comedones have a cyclical nature, either forming into inflammatory acne, re-appearing, or resolving.

Based on clinical experience, this cycle was estimated to take between 2-6 weeks. However, no studies had been done that provided direct evidence for this timeline.

A week after the comedone was extracted the skin appeared to resolve – to the naked eye. Under a microscope, however, researchers found that dead skin cells and sebum were already beginning to accumulate and reform the comedone.

This highlights the importance of continuing acne treatment even after the skin looks like it has cleared. This may also provide evidence for the use of acne treatments over the entire face or affected area instead of spot treating.

Further research with this technique could show how acne treatments prevent this comedone reformation, if there is individual variation on this reformation, what changes in the skin cells is causing the excess build up, and how long a lesion needs to be treated before the pore returns to normal.

"In vivo study of comedone reformation" on KindofStephen.

This paper found a correlation between the time that female subjects went to sleep and how much sebum their skin produced.

A slight increase in sebum production was seen the later they went to sleep. As well, sleeping less was correlated with a slight decrease in sebum production. This relationship wasn’t seen in the male participants of the study.

They also found a correlation between levels of free testosterone and 5α-reductase (an enzyme that converts testosterone in to dihydrotestosterone – a more active form).

Curiously this correlation was, again, only significant for women – despite men having 10 times more free testosterone than women. The researchers think that there may be a maximum threshold for how much testosterone can influence sebum production. There’s also research indicating that the sebaceous gland’s sensitivity to testosterone varies among individuals as well.

While the study’s sample size was quite small, and it’s completely possible this isn’t reproducible, due to random chance or some other variable…there is newer research describing a pathway between inflammation and sebum production – which may be what’s at play here.

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Depending on concentration and bioavailability, niacinamide has been shown to have antimicrobial, anti-inflammatory, photo-protective, sebum reducing, and lightening effects when applied topically.

Niacinamide is the amide form of niacin.

The OH (oxygen and hydrogen, or hydroxyl) molecules have been replaced by an amine group – the nitrogen and two hydrogen molecules.

There are other topical forms of niacin, where the hydroxyl group has been replaced by a fatty acid – but their use is patented (NIA24 products).

Niacin isn’t often used topically because it causes prostaglandin release, which results in skin flushing and itching. Niacinamide and other forms of niacin don’t have this undesirable side-effect.

Niacinamide is quite stable, but in the right conditions can hydrolyze (breakdown in water) to niacin.

This is a concern for manufacturers who need to ensure long-term stability of their products, but should not be of particular worry for people using a product containing niacinamide and then another containing an acid (or vice-versa).

The reason being is that this hydrolysis takes a considerable amount of time. At a pH of 2 and 90°C it takes over 75 hours to convert half of the niacinamide in to niacin. Heat greatly speeds up chemical interactions, and at normal temperatures this translates in to weeks, if not months.

While it’s certainly true and possible that a small amount of niacin will form, for most people it won’t be enough to cause skin flushing.

If you do notice skin flushing (and tingling), then space the two products further apart. But don’t worry too much, the bulk of the product is still in niacinamide form and niacin is involved in the same pathway that niacinamide is.

Addendum: There’s another paper that focuses on the interaction of ascorbic acid and niacinamide which is often brought out in this discussion.

The important part though is often missing – the interaction is minimal, reversible, and irrelevant at physiological pH.

Again, this is more of a concern for cosmetic manufacturers and not consumers mixing products.

Cool Fact: Topical niacin and the lack of flushing response could be used to help diagnose schizophrenia

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