What are the Daltons?
Daltons are a unit used in chemistry to express the mass of elements on an atomic scale.
500 Dalton’s Law
Active ingredients used in dermatology and cosmetics are measured in Dalton. When they are small they are measured in Da (daltons) and when they are larger they are measured in kDa (kilo daltons) or even MDA (mega daltons).
Thus, according to the Law of 500 Daltons, only particles that do not exceed 500 Daltons can penetrate the skin.
This is important, because the efficacy of a cosmetic or its active ingredients will be directly related to its ability to penetrate to reach its target cell. The easier it is to penetrate the skin, the more effective it is.
However, human skin has unique properties, which act as a barrier and prevent external agents from entering the body. For this reason, almost all topical products remain in the epidermis.
The outer layer of the skin is very thin, but it serves to protect us. However, particle absorption is not only dependent on penetration, but also on other variables such as skin metabolism.
Likewise, due to its hydrophobic nature, the stratum corneum will allow the entry of lipid-soluble molecules, while it will be more difficult for water-soluble compounds.
These soluble molecules have an alternative, which is to enter through the openings of the sweat glands and hair follicles. However, this opening is less than 0.1% of the total skin surface, so it is not very significant.
Small molecules can overcome the transdermal barrier and overcome the stratum corneum. Molecules whose molecular weight is greater than 500 Dalton cannot pass through the stratum corneum.
Which actives penetrate the skin?
Under these conditions, we might think that it is impossible to overcome the skin barrier.
However, some active ingredients, especially those with an oleic base, can enter the first layers of the skin, since theythe sealing of the epidermis is oily so it is permeable to oils, this allows some even somewhat large substances to reach the epidermis, but once there they cannot go deeper as they are oily.
The Law of 500 Daltons has an effect on standard formulations, but does not apply to encapsulations, which allow greater absorption and control to release the active ingredients.
But there are also anchorages to magnetic molecules, to noble metals, flexible encapsulations that adapt to any gap, ionized, etc.
The options to overcome the skin barrier and reach deeper and deeper levels are increasing, so we will be able to see more and better effects of actives on the skin.
Therefore, with encapsulation or by electroporation, it is possible to circumvent the main property of the skin. And, with ultrasound, we can increase the amount and depth of active ingredients that will enter the skin.