Dry vs. Dehydrated Skin

One of the most common confusions in skincare is that of dry and dehydrated skin. They both mean different things, are detected by different symptoms and need different treatments. The biologist in me couldn’t resist researching the two and thus the reason for my post today. So let’s get down to it...

THE DIFFERENCE: Dry skin is that lacking oil, dehydrated skin is that lacking water. Both can either be genetically determined or triggered by environmental factors, but it is important to realise which exactly you are suffering from (if any) as they both require different treatments. Dry skin is most commonly detected by a dull appearance, visible flaking or roughness and redness/sensitivity. Dehydrated skin often feels tight and irritated, appears dull and lines more visible. In many cases, dehydrated skin can appear quite oily in places where the sebaceous (oil) glands are over-reacting to compensate for the lack of moisture in the skin.

THE CAUSES: As we age, our sebaceous glands slowly decrease their oil-producing power house. As this natural hydrator slows, it is important we are applying more nourishing emollient-rich creams to compensate for the lack of lipid production. Aside from aging, if any of the genes corresponding for sebum or lipid production are impaired, the skin will not have optimum oil levels and thus will need replenishing creams. Weather forces such as sun and wind can rapidly suck moisture from the skin. UV radiation can also dehydrate the skin by damaging the precious cells which form the skin’s moisture barrier. Once holes form in this protective layer, the moisture barrier is much harder to maintain. Dehydration can also have a genetic root cause.

DEHYDRATION UP CLOSE: I am going to do my best to explain the biochemistry of how our skin maintains enough hydration. Our skin is made up of layers, as most of you may know. In the upper layers lies the moisture barrier, an area of specialised cells that work to lock water in the skin. The cells here are being constantly renewed and so it is important that the underlying mechanics are up to scratch to ensure this process is successful. Specialised keratin cells (the cell type that forms our skin, hair and nails) detach from the basal layer of the skin where they are produced. They then undergo a series of changes on a kind of conveyor belt as they make their way to the upper layers. One of these changes is the addition of moisture-grabbing proteins filaggrin and loricrin. Water-repellent lipids are also added to the keratin cells. This process of the cells making their way to the surface and changing form is known as ‘cornification’. The keratin cells change at the surface by all forming a giant matrix. Proteins from individual cells all join up to form a strong barrier (the moisture barrier) and lipids from inside the cells are released to create a water-repellent envelope around this matrix. Now, for the key players... Caspase-14 is an important enzyme in this cornification process. If you’re not aware, enzymes are a special kind of protein that increase the rate of biochemical reactions. They work by transforming specific molecules (here, Caspase-14 works on filaggrin) to form them into a completed product. In this case, if Caspase-14 or filaggrin are not present in high enough quantities, the moisture barrier will not be formed as completely and damage is more likely. Damage includes moisture evaporation (leading to dehydrated skin), and an increased risk of cell damage from UV-radiation.

The point of all this is that sometimes even if our diets are up to scratch and we’re leading healthy lifestyles, there can be a genetic root cause of dryness and dehydration. In this case, our only option is to venture along the treatment pathway. Products that are able to stimulate the production of things like sebum (if we suffer from dryness) or Caspase-14 and filaggrin (if dehydrated) are of course wonderful as the idea is that they help you to help yourself, but in the mean time make sure that you are going to go for a product to help your concern. Use emollient-rich creams for dryness and water-based creams aimed at repairing the moisture barrier and locking in moisture if dehydrated.

A couple ranges really worth looking at for dehydrated skin are Make a Difference™ by Origins and Vinosource by Caudalie. For dry skin, Oilateum Natural Repair Face Cream or Liz Earle's Skin Repair Moisturiser are great emollient-rich creams. Feel free to comment with any other suggestions! I hope this helped at least a little bit.

For further reading:
Denecker at al. (2008) JCB 180: 451-458