NIOXIN System 4 Leave-In Scalp & Hair Thickening Treatment — Colored Damaged Hair, UV Protection

NIOXIN System 4 Scalp & Hair Thickening Leave-In Treatment is a professional, leave-on formula designed to strengthen color-treated hair with progressed thinning while nourishing and protecting the scalp.

Built as the final step in the three-part NIOXIN System 4 regimen, this leave-in treatment combines antioxidants, botanicals and UV-protecting ingredients to improve hair diameter and refresh the scalp environment. It is formulated specifically for colored, damaged hair experiencing progressed thinning and works alongside the System 4 cleanser and conditioner to amplify hair structure and reduce breakage.

How does this treatment help hair feel thicker and more resilient?

The System 4 leave-in boosts hair diameter and supports strand resilience through ingredients that strengthen and coat the hair fiber. Consistent use after cleansing and conditioning helps reduce breakage and enhances the appearance of density without weighing color-treated hair down.

• Diameter-increasing formula that amplifies hair structure
• Strengthens strands to reduce breakage from styling and color damage
• Lightweight leave-in delivery to avoid buildup on color-treated hair

What does it do for the scalp and how is it applied?

This leave-in treatment refreshes and balances the scalp by delivering nourishing botanicals and antioxidants directly to the skin and hair roots. Apply to the scalp as the third step after shampooing with the System 4 cleanser and using the System 4 conditioner; work through to the ends for full coverage.

• Scalp Access Delivery System 2.0 targets scalp and follicle area
• Apply to dry or towel-dried hair as the final step in the system
• Works with regular cleansing and conditioning for best results

Will it protect colored hair and reduce visible thinning?

The formula includes UV-protection components and ingredients aimed at protecting against environmental stressors that can accelerate visible wear on color-treated hair. While results vary, many users report improved fullness, thickness and a refreshed scalp appearance when used consistently with the System 4 regimen.

• Contains UV-protecting ingredients to help shield color-treated hair
• Designed to complement professional System 4 shampoo and conditioner
• Clinical consumer feedback shows notable increases in perceived thickness and fullness

How quickly will I notice changes and how long should I use it?

Visible improvements in hair fullness and texture are often reported within weeks, with more substantial changes developing with continued use. For consistent maintenance and to support a healthier scalp environment, incorporate the leave-in into a regular routine alongside the other System 4 products.

• Many users notice changes in 30 days with regular use
• Best when used as part of the complete System 4 three-step program
• Ongoing use helps sustain the scalp environment and hair appearance

Who is this for: NIOXIN System 4 Scalp & Hair Thickening Leave-In Treatment is intended for people with color-treated, damaged hair experiencing progressed thinning who want a professional-strength, lightweight leave-in to strengthen strands, improve hair diameter, and nurture scalp health. It suits those who follow a three-step regimen and seek added UV protection and botanical nourishment without compromising hair color or weight.

Ingredients

Aqua, Phenylbenzimidazole Sulfonic Acid, Niacinamide, Benzophenone-4, Caffeine, Polysorbate 20, Sodium Hydroxide, Benzyl Alcohol, Sodium Benzoate, Phenoxyethanol, PEG-12 Dimethicone, Citric Acid, Cocamidopropyl Betaine, Acetamide MEA, Isopropyl C12-15-Pareth-9 Carboxylate, Tetrasodium EDTA, Propylene Glycol, Methyl Nicotinate, Sodium Chloride, Parfum, Polysorbate 60, Polysorbate 80, Mentha Piperita Oil, Mentha Arvensis Leaf Oil, Menthol, PEG-23M, Camellia Sinensis Leaf Extract, Limonene, Cystine Bis-PG-Propyl Silanetriol, Biotin, Lecithin, Tocopheryl Acetate, Foeniculum Vulgare Fruit Extract, Silica, Faex Extract, Acer Saccharum Extract, Citrus Limon Peel Extract, Saccharum Officinarum Extract, Vaccinium Myrtillus Leaf Extract, Citrus Aurantium Dulcis Fruit Extract, Potassium Sorbate