I have written before about how I don’t think that there is very much value in the comedogenic scale that attempts to rate cosmetic ingredient for their potential to cause blackheads. But this rather begs the question, posed to me by Livvi on Twitter, what ingredients do cause them? Livvi actually asked what ingredients block pores – but although blocking pores doesn’t automatically mean blackheads, that is the main problem. Phew, this is a bit of a tough one. One of the most intriguing things is the way that the effect on pores is such an individual thing. A product can be a real problem for one person and have no effect at all on others. We are of course all different. But what exactly is it about our pores that varies so much?
The obvious thing is pore size. Maybe some people have pores that are smaller and easier to block. That might well be a big part of it. The other thing that will vary from person to person is the chemistry of the oils in their skin. This might prove to be something that is quite a bit deeper than you might initially think.
One of the components of the skin are small levels of materials called fatty acids. These are a natural breakdown product of the skin’s oils and so it is not surprising to find them there. What is a bit surprising is that they have an antibacterial effect. This could just be a coincidence, but possibly these fatty acids play an important role in protecting the skin from infection.
The interesting thing to know, and I don’t think anyone has ever studied this, is whether or not the production of these fatty acids was controlled by the body’s immune system. If so that might well mean that perturbing the surface of the skin by applying a cosmetic product to it might have some quite unexpected side effects. A component of a cosmetic product might well have the effect of making the area to which it was applied temporarily less resistant to microbial attack. Perhaps this would give the bacteria that cause blackheads, and whiteheads and even acne their chance to get into the pores.
What kind of ingredients might have this kind of effect? It is hard to say. Maybe other fatty acids or things that are similar to fatty acids might replace the ones that should be there. There are piles of ingredients that fall into this category. Stearic acid is a fairly commonly used one. But the ingredient list on the pack isn’t going to much help here. Stearic acid won’t always be in the same form in different products, and may not work in the same way in different formulations.
Another possible interaction is where the product reacts with the skin’s oils to block the pores. This is the basis of the deliberate blocking of the pores by antiperspirants. The active ingredient is aluminium. Aluminium is a highly charged material that can react with fatty acids to produce larger hard to shift molecules that prevent sweating. There are other metal ions that can have the same effect, albeit not so strongly. Magnesium and calcium are couple that turn up in cosmetic formulations.
(If you know a bit of chemistry, as I think Livvi does she blogs at Open Bio, polyvalent ions are the things to look out for.) Again the exact form that they are present in is important so the ingredient list isn’t going to be any guide to whether a particular product is good or bad. So basically there isn’t much to say about what kinds of things are likely to give you problems with your pores. All I can offer is some speculations.