Today I’d like to discuss what exactly it is that differentiates dry skin from dehydrated skin, as this is something that seems to cause some consternation among people who come to me!
What we call dry skin is caused by a lack of both oil and water in the outer layers of the dermis – i.e. the skin that you see. Oil production in the skin is due to a process of sebum production from the sebaceous gland. Sebum is a waxy substance that helps to lubricate and waterproof the skin. When the levels of production are low we can see the results – dry, cracked skin and uncomfortable rashes and itching.
Skin hydration, on the other hand, is down to what we call NMF – the natural moisturizing factor. The skin cells contain a certain level of water, which helps to form a natural barrier against environmental factors such as dust and pollution. When the cells fail to contain an adequate amount of water it leads to a similar condition as that of low oil production – discomfort, itching etc.
‘Dry’ skin is due to a combination of both these factors. ‘Dehydrated’ skin, however, is solely due to a lack of water to protect the epidermis, and has less association with oil production. It is hugely important to correctly identify the cause of any skin problem you may be suffering with, as the wrong treatment can have unpleasant effects!
A lack of oil in the skin can often be put down to the effects of aging. The sebaceous gland produces less sebum the older we get (study: http://www.ncbi.nlm.nih.gov/pubmed/3668294), and this deterioration in sebum levels can cause the skin to become dry. A lack of water in the dermis, on the other hand, is more often than not down to environmental factors – heat, pollution etc. The other reason, of course, is not drinking enough water! I would recommend a daily fluid intake of at least 1.5 litres. Any excess fluid will be excreted from the body anyway, so unless you go mad and drink 10 litres or more it’s difficult to do yourself any harm!
If the outer dermal layers are not kept hydrated it becomes difficult to form a robust barrier, which leads to any fluid that is there evaporating more easily than it should. The epidermis becomes thinner with age – the areas available to hydrate become ever smaller, leaving the skin prone to dryness.
In addition, over-indulgence in alcohol or salty and fatty foods can cause the skin to get out of balance, so, as always, be careful with your diet!
In the next blog I’ll be talking about how best to treat dry or dehydrated skin, so please join me!