Chronologiste Overnight Youth Serum
An overnight age-support hair serum designed to deeply hydrate, smooth, and help improve body and softness from root to tip.
A more premium overnight option for people focused on aging hair, dryness, softness, and a more revived-feeling finish by morning.
The Chronologiste line commands the highest price point in the Kérastase range precisely because of its prestige active (Pro-Xylane) and its position as the brand's "age-reversal" haircare answer. For anyone who has invested in their skincare anti-aging routine and wants the same level of formulation intention applied to their hair, Chronologiste is the answer Kérastase gives them.
Last step of the evening haircare routine — applied to lengths after any scalp serums. Leave in overnight; no rinse needed.
People who treat their haircare with the same seriousness as their skincare and want a premium overnight treatment at the level of their skincare routine. Particularly compelling for anyone who notices their hair has changed with age — less body, softer, drier, less vibrant.
If fine hair is already oily or lacks volume — the overnight weight of even a light serum can exacerbate flatness. Best for dry, coarse, or genuinely aging hair that needs the extra moisture dose.
If hair feels overloaded or weighed down, reduce the amount and focus only on the last inch of ends. The serum may be too rich for the hair's current state — a reset wash and lighter application will recalibrate.
- The full Kérastase Chronologiste shampoo, conditioner, and mask system for a complete age-support haircare routine
- The Genesis Serum Fortifiant on the scalp before the Chronologiste serum on the lengths for a full leave-in routine
- A weekly use of the Chronologiste mask or balm as a deeper weekend treatment to complement the daily overnight serum
Best For
- Dry hair
- Thinning-looking hair
- Aging hair
- Overnight hydration
- Smoother texture
- Body and softness
How to Use
Apply to lengths and ends before bed as directed by the brand. Leave in overnight without rinsing. Style as normal in the morning.
Key Ingredients
Pro-Xylane was originally developed for prestige skincare (used in brands like Helena Rubinstein and Lancôme) for its ability to stimulate glycosaminoglycans in the dermal matrix — essentially the structural support molecules that keep skin plump and hydrated. When applied to hair, it supports the hair fibre's internal moisture structure, helping to restore softness, body, and hydration to dry or aging hair. It is Kérastase's signature prestige active for the Chronologiste "youth support" haircare line.
Algae extracts deliver marine-sourced minerals (iodine, magnesium, potassium, calcium), polysaccharides (hydrating film-formers), polyphenolic antioxidants, and amino acids to the skin or hair. In haircare, they support hydration, softness, and scalp mineral balance. In skincare, they function as humectants, antioxidants, and soothing agents. Specific algae types have more targeted actions — Spirulina for protein support, Laminaria for mineral richness, Fucus for antioxidant polyphenols.
Draws moisture to the skin, helps maintain hydration, and reinforces the skin barrier.
Fragrance has no skincare function — it is added purely for sensory appeal and brand experience. Some fragrant ingredients (like linalool, limonene, and eugenol) are known sensitizers that can cause contact dermatitis in sensitive individuals over repeated exposure.
Ingredients to Note
May be a concern for some skin types. Tap to learn more.
Full Ingredient List
About This Product
Kérastase Chronologiste is the brand's prestige anti-ageing haircare line — built around the concept that hair, like skin, shows visible signs of ageing: loss of density, moisture, softness, and body over time. The Overnight Youth Serum is the nighttime treatment in this collection, using a leave-in overnight format to deliver deep hydration and softness support while you sleep. Key to the Chronologiste philosophy is Pro-Xylane — a patented active (from L'Oréal's research arm, which owns Kérastase) originally developed for prestige skincare and known for its barrier-support and cellular hydration properties. In a haircare context, Pro-Xylane is used to support the hair's internal moisture structure. Combined with algae-derived actives and an overnight delivery system, this serum positions itself as the most premium haircare overnight treatment in Kérastase's lineup.