NIOXIN System 4 Scalp + Hair Thickening Treatment — 6.8 fl oz leave-in serum for color-treated, damaged hair | strengthens, increa

This professional-grade leave-in treatment finishes NIOXIN’s three-step System 4 regimen and is formulated specifically for color-treated or chemically damaged hair showing progressed thinning. It delivers antioxidants, botanicals, and UV-protecting ingredients via NIOXIN’s Scalp Access Delivery System 2.0 to create a refreshed scalp environment and visibly amplify hair structure without weighing strands down.

How does this treatment strengthen and thicken hair?

The formula targets weakened hair fibers and the scalp to reduce breakage and to increase the visible diameter of each strand. Applied after cleansing and conditioning within the System 4 kit, the leave-in serum works to fortify hair resilience and support fuller-looking hair in weeks.

• Contains strengthening agents that reinforce hair shaft integrity.
• Delivers scalp-nourishing antioxidants and botanicals to the root environment.
• Leaves hair feeling thicker without heavy residue.

What makes this suitable for colored or damaged hair?

System 4 is formulated to protect color-treated hair while addressing progressed thinning—balancing scalp health and protecting strand structure. UV-protection and gentle conditioning ingredients help preserve color vibrancy while the treatment reduces hair loss due to breakage.

• UV-protection ingredients shield color from fading.
• Gentle, non-stripping delivery to avoid adding stress to treated hair.
• Designed to work with the System 4 cleanser and conditioner for best results.

How should I use it within the three-part NIOXIN regimen?

Use this leave-in serum as the final step after the System 4 Cleanser Shampoo and Scalp Therapy Conditioner. Apply to a towel-dried scalp and hair, comb through, and style as usual; no rinse needed so active ingredients remain at the scalp and along the strand.

• Apply a few pumps directly to the scalp and roots on damp hair.
• Distribute evenly with fingertips or a comb to target thinning areas.
• Use consistently with System 4 for visible improvements in structure and fullness.

What practical results can I expect and when?

Users report noticeable changes in hair thickness and density with regular use; many see visible improvements within about 30 days when used as directed. The treatment focuses on reducing breakage, refreshing the scalp, and enhancing fullness, rather than making clinical growth promises.

• Reported increase in perceived hair fullness and density.
• Helps minimize breakage that contributes to thinning appearance.
• Maintains scalp balance and reduces buildup that can hinder healthy hair appearance.

Who is this for: NIOXIN System 4 Scalp + Hair Thickening Treatment is intended for people with color-treated, chemically processed, or damaged hair experiencing progressed thinning who want a salon-strength, leave-in solution. It’s best for those already using or willing to follow the three-step NIOXIN System 4 routine and who seek to strengthen strands, refresh their scalp environment, and enhance hair diameter without compromising color.

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