How to tell whether you have dry or dehydrated skin (it’s more complicated than you’d think)

Working out whether you have dry skin or whether you have dehydrated skin could solve all your skincare woes and enable you to provide the ingredients your skin actually needs, rather than applying the entire bathroom shelf to no avail. But, um, how do you tell the difference between dehydrated and dry skin? Aren’t they basically the same thing?

Ask any dermatologist and the short answer is no, they’re most definitely not the same thing. Whilst there’s a lot of cross over between the two (so, you’d be forgiven for getting them confused), they’re fundamentally different and require different treatment.

The problem is, dry skin can masquerade as dehydration and vice versa. Both can leave skin feeling rough, tight and irritated, so how can you tell which is which?

What is dry skin?

Dry skin is a skin type, which doesn’t change and fluctuate depending on the seasons, your diet and the environment. “The cause for dry skin is a lack of sufficient biosynthesis of natural lipids [the skin’s fats and oils] and/or water-holding substances,” explains Dr Stefanie Williams, Consultant Dermatologist and Medical Director of EUDELO. It’s caused by a lack of sebum (or oils) in your skin as well as a weak skin barrier, which can mean your skin struggles to keep the protective oils, or lipids, it produces in.

What is dehydrated skin?

Dehydrated skin is a skin condition which can change and fluctuate depending on the seasons, your diet and the environment. It’s caused by a lack of water and can affect any skin type, so even if you’re oily, your skin can also be dehydrated. One of the main causes of dehydration is not drinking enough water, but it can also be caused by hot showers, UVA from sunlight, weather changes, central heating and your diet (too much caffeine and salt for instance).

What’s the difference between them?

“With dry skin you may notice a scaly appearance, white flakes, redness or irritation and increased incidence of psoriasis, eczema or dermatitis,” explains Dr Dianni Dai, skin specialist at the Pulse Light Clinic. “With dehydrated skin, on the other hand, you might notice, darker under eyes, itchiness, dullness or more sensitive fine lines and wrinkles,” she adds. You might also experience more congestion and breakouts.

As far as what causes them, “sometimes, the term ‘dehydrated skin’ is used to describe more extrinsically caused reduction of water content in the stratum corneum (e.g. dehydration of the skin caused by excessive cleansing),” says Dr Stefanie, “while ‘dry skin’ may be used to describe a genetic predisposition for dry skin (for examples in individuals with a tendency for eczema).”

What are the similarities between them?

Since a weakened barrier function is one of the main problems for people with dry skin, “the consequence is that the skin can’t hold on to its natural water [or oily lipid] content sufficiently and will lose too much water via (invisible) evaporation,” says Dr Stefanie. “This increased evaporation (aka TEWL, trans-epidermal water loss) then leads to dehydrated skin.