Your goal with a topical is to choose one that will do no harm AND just might make it to the dermal/epidermal junction where it will do its metabolic magic.

There is so much in the way of that. But let’s be positive before we go into the weeds.

The skin limits penetration first of all by molecular weight or mass – which is also related to size of the molecule, at least in typical skincare chemicals. That means anything larger than 750 daltons in molecule size is not going to get past the door bouncer.

Which also means that proteins and stem cells that are about 10 million daltons are just going to sit on top of the skin like beached whales and degrade there. In the case of proteins this might mean they breakdown into their component amino acids – when this happens you often will get little white bumps (acids do that), especially around your eyes where protein products are usually applied to help stiffen up loose eye skin.

But actives like Vitamins A, B, C, E and there are many variants of these, along with say the Avogen 302 molecule from 302 Skincare are all in the 300 daltons molecular weight range so they often will be able to penetrate deeply into the skin.

Many natural substances especially OIL, FATS & LIPIDS can easily go deep into the skin, unlike water soluble substances.

The exceptions are silicone oils like dimethicones that do not penetrate past the surface. This characteristic makes these very desirable molecules, if they are low viscosity (very light texture, they feel like air), to keep the skin moisturized. They can be pore clogging if heavier in molecular weight though and when combined with minerals as found in makeup the skin can become easily clogged and prone to breakouts.

Sidebar: The Skin Dork is not a fan of spreadable makeup for that very reason. It’s not the dimethicone or the mineral powder alone that are the problem, it is the combination of the two that clogs the skin and leads to problems.

With ingredients that are water soluble, like water itself, the skin will tend to reservoir these ingredients. So, glycols and surfactants and glycerine and so many others that are below 750 weight will go into the skin but get arrested before they get far. The skin swells up a bit from the water soluble products so your skin looks plump and you are pleased. Polyphenols which are the metabolites found in plant extracts can penetrate into the skin and tend to break down quickly into simple hydrocarbons.

When the skin reservoirs the skincare ingredients it will send in enzymes to break down the complex chemicals you applied in order to use them or throw them out. This takes a lot of energy. Most metabolites from natural products use up more skin energy than they supply. Think of peas in the soil – they add nitrogen to it, which is very desirable. Cotton on the other hand depletes the soil rapidly. Putting a lot of chemicals on weak skin can weaken it further. You wear out the soil.

A big reason for that is the amount of product you apply goes into a very small space. Over application of a product isn’t helping. Over frequent application is a very bad idea, too. Very.

The skincare ingredients you put in your skin should at the very least help form desirable skin protein by sourcing energy from available nutrients like glucose. Most skincare products do not help and form undesirable fragmented proteins that are like sand bags and meant only to prevent further invasion by the products you are applying. This is the process of inflammation.

A very few ingredients will reach the dermis. VITAMIN C is one of these. You want a Vitamin C molecule that is not photo-reactive AND is not a charged molecule. Ascorbic acid (the charged molecule of vitamin C) is very unstable, photoreactive and exposure to the air for even a minute can break it down to an oxidized mess. So chemists have found a way to create ester forms of Vitamin C and the skin is much more receptive to those. But Vitamin C should be applied only at night and stay out of the sun the next day.

Application of Vitamin C esters will often reach the dermis and make contact with specific receptors. This is a win-win. But after an initial increase in skin protein and some other beneficial weeding and feeding, things can go rapidly downhill. Over-application, that is, too frequent an application will see receptors shut down and all the gains will quickly reverse, the skin will treat the Vitamin C like a toxic chemical.

Continued application of Vitamin C esters can lead to addiction, dependency, weakness, flare-ups, rosacea and if not discontinued altogether, dermatitis.

Rule of thumb: if you get a great visual result with a product, reduce your frequency of its use immediately to once or twice per week. More frequent application will create problems. The skin cannot handle the chemical load you are dumping into it.

Skincare products often have this double edge quality about them. The penetration of the product ingredients into the skin may be very efficient but once there, bad things can happen especially if over application frequency of strong metabolites is in play.

Always be aware of the sensitivity of your skin to process topical products. The skin is not a food processing facility. It is like a houseplant that responds well to a bit of nourishment now and then and a splash of water.

But overfeed it with strong metabolites and soak it frequently in deeply penetrating moisturizing chemistry and you will see a drab, unresponsive visible deterioration. Surprise the skin with metabolites, don’t beat it over the head with them until morale improves.