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The TLDR of TEWL (in other words, how to avoid dehydrated skin).

Isn't just the worst when you're in a hurry, and you've done your morning skincare, applied the recommended amount of sunscreen (read: a lot!), and then you're about to move onto your foundation or concealer or tinted moisturiser (or serum foundation, the list goes on), and - what's this? Flaky skin!

There are so many reasons you might suddenly be experiencing dry skin - the tretinoin/retinol 'uglies', you might have a little sun burn, chapped skin from the wind or cold, or maybe you've gone hell for leather on the physical exfoliants this week and now you're paying for it.

Whatever it is, you need to get on board with managing your TEWL - transepidermal water loss, that is. Essentially, this is the water that passes through your epidermis to the outside world and evaporates - everyone wants a piece of your hydration! Some days you'll lose more, some days less - if your body can't replace it that's when you'll get that tight feeling (even if you have combination or oily skin).

To slow this process and hold onto the water content in your skin, you want to look at this from two angles - you need to have some water content there in the first place, and then you need to lock it in.

A really easy (and free!) first step is to apply your skincare onto a damp face - in fact, some people recommend not even towel drying, so if you can just air dry a little (soaking wet won't work), mist on your hydrating toners, essences and apply your serums while your skin has water on it. And no matter how chilly it is - no hot water on the face, as this only speeds up the TEWL and ruins your hard work.

Now the next step may be too heavy for daytime use, but at night, you want to lock in that damp skin, misted and serum-ed up, with an occlusive moisturiser - this means one that will create a film over the skin and will lock in the moisture, trapping it close to the skin for more of the night. Vaseline and other petrolatum-based products are the gold standard for this (and this isn't a black-and-white area given the source of petrolatum), so jojoba oil and shea butter can also work well - just make sure it's something that hasn't caused your skin trouble in the past. The trick here is not to get fancy with it, you aren't looking for a multi-ingredient occlusive power blend with some AHA and ceramides as well, it's kind of like wearing a plastic poncho for a water ride at a theme park, it's not meant to look good, it's just meant to do the job.

This process is otherwise known as 'slugging', adding a substantial layer of an occlusive over your evening skincare and waking up to reveal smooth, hydrated skin. Like most trends in skincare (although this really is one of the steps derms have been on about for years, but now we have a fun new name for it), there is potential for irritation - some experts believe locking in actives like tretinoin with an occlusive can heighten potential for redness and stinging, but for the most part, this is a pretty risk-free addition to your current routine.

The end result should mean you spend less time prepping your skin each day, and spend less money on new pots of moisturiser each month, because your skin is able to function as intended. It's a win-win!


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