A daily strengthening treatment for brittle, splitting nails
ISDIN Si-Nails Nail Hardener is a strengthening treatment for weak, brittle nails that split, peel or break easily. Its formula is built around organic silicon (silanediol salicylate), which helps reinforce the structure of the nail, together with cationic hyaluronic acid that keeps the nail hydrated and more flexible, so it bends rather than snaps. Mastic gum from Pistacia lentiscus forms a protective film on the surface while the nail grows out. Used every day for several weeks, it leaves nails harder, smoother and less prone to breakage.
The texture
A clear, fast-drying liquid applied with a fine brush. It leaves a discreet film on the nail and dries in a minute or two.
Who it suits
- Brittle nails that split, peel or break
- Soft nails that bend easily
- Nails weakened by frequent hand-washing or cleaning products
- Nails recovering after gel or acrylic manicures
Worth knowing before you buy: It contains denatured alcohol and a paraben (methylparaben). Strengthening takes steady daily use over several weeks, so results are not instant. Pair it with a hand and nail cream to keep the cuticles supple.
How long one tube lasts
Applied once a day on all ten fingernails, the 2.5ml tube lasts around two months.
Complete the routine

Vinotherapist Hand Cream
Nourishes hands, nails and cuticles.
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Ecrinal Nail Serum
Precious oils for dry, damaged nails.
Shop →Characteristics
- Texture: liquid, brush applicator
- For: weak, brittle, soft nails
- Concerns: brittleness, splitting, peeling, breakage
- When to apply: once a day
- Main benefits: strengthens and hardens nails, keeps them hydrated and flexible, forms a protective film
How to use
Apply once a day to clean, dry nails with the brush, covering the whole nail surface, and let it dry. Use daily for several weeks.
Active ingredients
- Organic silicon (silanediol salicylate): helps reinforce the nail structure
- Cationic hyaluronic acid (hydroxypropyltrimonium hyaluronate): hydrates the nail and keeps it flexible
- Mastic gum (Pistacia lentiscus): forms a protective film on the nail
Ingredients
AQUA (WATER) · ALCOHOL DENAT · PEG-40 HYDROGENATED CASTOR OIL · BUTYLENE GLYCOL · ACRYLATES COPOLYMER · SILANEDIOL SALICYLATE · TROMETHAMINE · CAPRYLIC/CAPRIC TRIGLYCERIDE · HYDROXYPROPYLTRIMONIUM HYALURONATE · TRIETHANOLAMINE · BIOSACCHARIDE GUM-2 · PISTACIA LENTISCUS (MASTIC) GUM · PROPYLENE GLYCOL · PHENOXYETHANOL · BENZYL ALCOHOL · METHYLPARABEN
Formulations are updated by the manufacturer from time to time. Always check the packaging you receive.
Manufacturer information
Brand: ISDIN S.A.
Address: Provençals 33, 08019 Barcelona, Spain
EAN: 8429420175839
