You know the feeling: after a day in the sun, your skin feels tight, dry, and slightly irritated. You dutifully applied sunscreen, maybe even used an after sun, yet your skin feels parched. Chances are TEWL - transepidermal water loss - is the culprit. A term that sounds like it belongs in a dermatology textbook, but is actually quite simple to understand. And most importantly: entirely preventable.
In this article, we explain what TEWL is, why it gets worse in summer, and which Bioderma products can help protect your skin. Of course, we also compare prices at Belgian online pharmacies.
What is TEWL and why should you care?
Transepidermal water loss is the process by which water evaporates from the deeper skin layers through the epidermis to the outside. In small amounts, this is perfectly normal. But when evaporation accelerates, your skin loses its natural moisture balance.
Think of your skin as a brick wall: the skin cells are the bricks, and the lipids between them form the mortar. As long as that mortar stays intact, moisture stays in. But once cracks appear - from sun, wind, chlorine, air conditioning, or harsh cleansing products - water starts escaping.
Why does TEWL get worse in summer?
- UV radiation damages the skin barrier and accelerates moisture loss
- Air conditioning sucks humidity from the air (and your skin)
- Chlorine and salt water strip your skin's natural oils
- Sweating changes your skin's pH, weakening its barrier function
- More frequent showers with hot water and soap remove protective lipids
The result? Your skin may look oily on the surface (due to excess sebum production as compensation) but is bone-dry underneath. Dermatologists call this 'dehydrated oily skin' - one of the most common summer skin problems.
The three pillars of summer hydration
Pillar 1: Protect - sunscreen is non-negotiable
Wear sunscreen every day. Not just at the beach, but when sitting on a terrace, walking to the shops, or working near a window. UVA rays penetrate glass and clouds. Choose at least SPF30, preferably SPF50 for sensitive or fair skin. Reapply every two hours, more often if you sweat or swim.
The Bioderma Photoderm Brume invisible SPF50+ Spray 150ml is an excellent choice. This invisible spray feels light, leaves no white cast, and is perfect for reapplying over makeup. Available from €18.13 at Belgian online pharmacies.
Compare prices on PharmaCompare →
If you prefer a richer milk texture, the Bioderma Photoderm Ultra SPF50+ Milk 200ml offers the same high protection in a more hydrating formula, ideal for the body. From €16.77.
Compare prices on PharmaCompare →
Pillar 2: Repair - after sun is not a luxury
After a day in the sun, your skin needs recovery time. The Bioderma Photoderm Aftersun Gel-cream 500ml is a solid recommendation. The gel-cream texture cools immediately and absorbs quickly without stickiness. The generous 500ml size is great value for daily summer use, priced at €16.94.
Compare prices on PharmaCompare →
Pillar 3: Hydrate - inside and out
Hydration starts with drinking water - at least 1.5 to 2 litres daily, more if you exercise or spend time in the heat. But your skin also needs topical hydration.
Here's a tip many people overlook: your cleanser plays a huge role in hydration. A harsh cleanser strips the skin of its natural oils, increasing TEWL. Choose a gentle, nourishing cleanser instead.
The Bioderma Atoderm Shower Oil 1L is ideal. This shower oil cleanses gently without compromising the skin barrier and leaves a protective layer that locks in moisture. Perfect after swimming or when your skin feels dry. The litre bottle is economical for daily use, available from €17.14.
Compare prices on PharmaCompare →
The same goes for your hair. Chlorine and sun dry out your hair, making it frizzy and brittle. The Bioderma Nodé Shampoo 400ml cleanses mildly and is suitable for daily use after swimming. From €12.14.
Compare prices on PharmaCompare →
Practical checklist
- Morning: moisturiser + SPF50 sunscreen (even on cloudy days)
- During the day: reapply every 2 hours, don't forget your lips
- After swimming: gentle cleanse with shower oil, not soap
- Evening: mild cleanser + restorative night cream
- Weekly: hydrating mask for an extra moisture boost
- Always: at least 2 litres of water daily
Belgian online pharmacies: where to find the best deals?
Pharmacies like Viata, Farmaline, and Medi-Market each have their own pricing strategy. Prices for the same product can differ by 20 to 30 percent. That's why it always pays to compare before ordering.
At PharmaCompare, we do that work for you. We collect prices daily from thousands of products at licensed Belgian online pharmacies, so you can see at a glance where you'll get the best deal.
Conclusion: invest in your skin barrier
TEWL is one of those invisible enemies silently dehydrating your skin while you think you're doing everything right. By investing in proper protection, repair, and hydration - and by shopping smarter with price comparison - you give your skin the best chance of looking healthy and radiant. Not just in summer, but all year round.
Curious about the sharpest prices for Bioderma products? Compare them now on PharmaCompare and save at your favourite Belgian online pharmacy.
This article was inspired by Keeping your skin hydrated this summer and avoid TEWL from Le French Skin Care Blog.