NIOXIN System 4 Scalp + Hair Thickening Treatment Serum 3.4 fl oz — for Color-Treated, Thinning Hair, Strengthens & Adds Diameter

Nioxin System 4 Scalp + Hair Thickening Treatment is a leave-in serum that refreshes the scalp and visibly increases hair diameter for color-treated, damaged hair experiencing progressed thinning.

This targeted finishing step is part of Nioxin's three-part System 4 and is formulated to fortify weakened strands while improving the scalp environment. The lightweight serum delivers a blend of nutrients, botanicals and antioxidants to help protect hair from breakage, support natural-looking fullness, and maintain color vibrancy without weighing hair down.

How does this treatment make hair look thicker?

The formula coats hair fibers to increase perceived diameter and lends a fuller appearance across the hair shaft. Over repeated use, it helps strengthen fragile strands so they resist breakage and appear more substantial.

• Leaves-in a diameter-increasing complex that amplifies strand thickness
• Strengthening ingredients reduce breakage that thins visible volume
• Designed to work with the System 4 regimen for cumulative results

Will it work on color-treated or chemically damaged hair?

Yes — this edition of System 4 is specifically tailored for color-treated and damaged hair with progressed thinning. The lightweight serum helps preserve color integrity while addressing the weakened structure that follows chemical services.

• Formulated to be safe for color-treated hair
• Contains antioxidants and UV-protecting elements to defend against environmental stressors
• Helps restore a healthier scalp base to support resilient colored strands

How should I use the Scalp + Hair Thickening Treatment?

Use as the finishing step in the three-part Nioxin System 4 routine: apply to a towel-dried scalp and hair, then style as usual. The leave-in serum is designed for daily or regular use and absorbs without leaving heavy residue.

• Apply directly to the scalp and throughout lengths after cleansing and conditioner steps
• Massage gently to ensure even distribution and scalp access
• Do not rinse out; style normally to maintain added body and manageability

What scalp benefits does this treatment provide?

The product cleanses and refreshes the scalp environment to reduce buildup that can stress follicles. By delivering botanicals and nutrients to the scalp, it supports conditions that are more favorable for stronger-looking hair.

• Helps remove excess sebum and impurities that can block follicle access
• Delivers antioxidants and botanical extracts to nurture the scalp surface
• Creates a refreshed base that complements the System 4 strengthening protocol

Who is this for: Nioxin System 4 Scalp + Hair Thickening Treatment is best suited for people with color-treated or chemically processed hair that shows progressed thinning and visible breakage. It’s intended for users who want a lightweight, leave-in booster that supports fuller-looking hair while protecting color and improving the scalp environment. Ideal when used consistently as the finishing step in the full System 4 regimen, especially for those seeking a salon-grade approach to strengthening fragile, treated hair.

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