Hydra No1 Sérum is Yon-Ka's hydration hero and the single product most people should start the brand with. It is a light gel-serum built around micro-molecular hyaluronic acid, and it exists for a problem most Canadians have from October onward: skin that is dehydrated rather than dry.
Quick answers
- What is it?
- Yon-Ka Hydra No1 Sérum, 30 ml, $120. A lightweight hydrating gel-serum.
- Who is it for?
- Any skin type that reads dehydrated. Oily skin included, which surprises people.
- How do I use it?
- Two to three pumps on damp skin, face and neck, morning and evening, before moisturizer.
- Do I still need a moisturizer?
- Yes. A serum brings water in, a moisturizer keeps it there. They are not alternatives.
- Dry or dehydrated?
- Dry skin lacks oil. Dehydrated skin lacks water. This serum is for the second one, and you can be both.
Dry skin or dehydrated skin
These get used interchangeably and they are not the same thing, and the distinction decides which product you should be buying.
| Dry skin | Dehydrated skin | |
|---|---|---|
| What it lacks | Oil | Water |
| What it is | A skin type. Relatively fixed. | A condition. Comes and goes. |
| How it looks | Flaky, rough, tight all over | Dull, papery, fine lines that appear overnight |
| Can oily skin have it | No, by definition | Yes, and often does |
| What it needs | Richer moisturizer, lipids | Humectants, then something to seal them in |
The giveaway is oily skin that still feels tight, or fine lines that look worse some mornings than others and cannot possibly have appeared overnight. That is dehydration, and it is the most common reason a routine stops working in a Canadian autumn without anything in it having changed.
Indoor heating, not outdoor cold, is the usual culprit. Once the furnace comes on, indoor humidity drops sharply and stays low until spring. Skin that was perfectly happy in September starts reading dehydrated in November on exactly the same routine.
What the serum is
Hydra No1
Sérum
Hydra No1
Crème
Hydra No1 Sérum is 30 ml at $120. Yon-Ka describes it as an intensely hydrating gel-serum for dry and dehydrated skin, and the texture is genuinely light: it absorbs quickly and does not leave the tackiness that a lot of hyaluronic serums do.
Yon-Ka lists the formula as 93% naturally derived, which is high for a serum in this category and consistent with how the brand has formulated since 1954.
The formula
| Ingredient | The job |
|---|---|
| Micro-molecular hyaluronic acid | Attracts and binds moisture at multiple levels of the skin, rather than sitting only on the surface. |
| Imperata cylindrica | A natural humectant from a grass that grows in arid conditions, used to help skin retain water. |
| Aloe vera | Soothes and calms the feeling of tightness. |
| Olive phytosqualane | Anti-dehydration, and part of why the finish is comfortable rather than tacky. |
| Vitamins E, C and A | Antioxidant support alongside the hydration. |
| Rose, chamomile and jasmine oils | The aromatic side of the formula, balancing and relaxing. |
The pairing of micro-molecular hyaluronic acid with imperata cylindrica is the part that matters. Hyaluronic acid draws water in, the grass extract helps hold it there. A humectant on its own in a dry room can leave skin feeling worse rather than better, which is the usual complaint about cheap hyaluronic serums in winter.
The Hydra No1 family
Yon-Ka builds Hydra No1 as a full family rather than a single product, so you can match the texture to your skin without leaving the range.
Sérum
Crème
Fluide
Masque
The Crème and the Fluide are the same idea in two textures, so pick one, not both. Hydra No1 Crème if your skin runs dry or sensitive, Hydra No1 Fluide if it runs normal to oily. Hydra No1 Masque is the occasional add-on, once or twice a week when skin needs more than the daily routine gives it.
If you want to add hydration without changing your moisturizer at all, Hydra + Booster at $88 is designed to be mixed into whatever cream you already own. That is the low-commitment route.
How to use it
- Cleanse, then leave skin slightly damp rather than towel-dry.
- Two to three pumps, pressed into face and neck. Press rather than rub.
- Wait about thirty seconds for it to absorb.
- Moisturizer over the top, every time. This step is what stops the hydration evaporating.
- Morning and evening. It is light enough to sit under sunscreen and makeup without pilling.
Applying to damp skin is not a nicety, it is how humectants are meant to work. A hyaluronic serum applied to bone-dry skin in a heated room has less to draw on, and that is the single most common reason people conclude a hydrating serum "does nothing".
Layering with other brands
You do not need to move your whole routine to Yon-Ka for this to be useful. A hydrating serum is one of the easiest products to slot into an existing regimen.
- With a vitamin C. Vitamin C first on clean skin, then Hydra No1 Sérum, then moisturizer.
- With a retinoid. Apply the serum first as a buffer, then your retinoid, then a moisturizer. The dryness of retinoid weeks is exactly what this is good for.
- With a richer moisturizer. Alastin Ultra Nourishing over the top is a strong combination for dry, dehydrated winter skin: water in from the serum, lipids and barrier support from the cream.
- With an exfoliating acid. Use the acid on its own schedule, and the serum on the nights in between.
We are an authorized Canadian retailer of Yon-Ka Paris. Free shipping on orders $99+, and samples with every order.
Shop Hydra No1 SérumFrequently asked questions
What is Yon-Ka Hydra No1 Sérum used for?
It is a lightweight hydrating gel-serum for dry and dehydrated skin, 30 ml at $120. It is built around micro-molecular hyaluronic acid with imperata cylindrica, aloe vera and olive phytosqualane, and Yon-Ka lists the formula as 93% naturally derived.
What is the difference between dry skin and dehydrated skin?
Dry skin lacks oil and is a skin type. Dehydrated skin lacks water and is a temporary condition that any skin type can have, including oily skin. Hydra No1 Sérum is aimed at dehydration, which is why it suits oily skin that still feels tight.
Can oily skin use a hydrating serum?
Yes, and oily skin is often dehydrated. A light gel-serum adds water without adding oil, and pairing it with the lighter Hydra No1 Fluide rather than the Crème keeps the whole routine weightless.
Do I still need a moisturizer if I use a hydrating serum?
Yes. The serum brings water into the skin and the moisturizer is what keeps it there. Using a humectant serum with nothing over it, particularly in a heated indoor environment, is the most common reason people feel a hydrating serum is not working.
Should I use Hydra No1 Crème or Hydra No1 Fluide?
Choose one, not both. The Crème at $106 suits dry and sensitive skin, and the Fluide at the same price suits normal to oily skin. They are the same concept in two textures.
Can I use it with a retinol or vitamin C from another brand?
Yes. With vitamin C, apply the vitamin C to clean skin first, then the serum, then moisturizer. With a retinoid, applying the serum first can act as a buffer. Introduce one new product at a time so you can tell what is doing what.
Where can I buy Yon-Ka in Canada?
From an authorized Canadian retailer. Your Skin Solution is an authorized Yon-Ka Paris retailer, with free shipping on orders over $99 within Canada and samples with every order.
Product names, sizes and ingredient descriptions are as published by Yon-Ka Paris. Prices are current as of 11 September 2026 and may change. Descriptions refer to visible, cosmetic change in the appearance of skin. Individual results vary. This article is general information and is not medical advice. Yon-Ka formulas contain essential oils. If you have a known sensitivity to botanical fragrance, patch test first or speak to a clinician.