Men and women with color-treated hair experiencing progressed (more advanced, noticeable) thinning — Nioxin's System 4 specifically, as opposed to Systems 1-3, which are formulated for natural (non-colored) hair or earlier-stage thinning. It's a consumer at-home product, not an in-salon professional treatment, and is meant to be used alongside the matching System 4 shampoo and leave-in scalp treatment rather than on its own.

Progressed thinning on color-treated hair creates a specific problem: hair still needs conditioning to stay manageable, but heavier conditioners tend to coat fine strands, make thinning more visible, and can be harder on a color-treated cuticle. System 4's conditioner is formulated to balance those two needs at once, and it's built to be used as the middle step of a shampoo-condition-treat sequence, which is how Nioxin designed it to perform rather than as an isolated product.

Use after washing with Nioxin System 4 Cleanser Shampoo. Apply the conditioner from the scalp through to the ends, leave on for 1 to 3 minutes, then rinse thoroughly. Follow with the System 4 Scalp & Hair Treatment (leave-in) as the third step. Intended for daily use as part of the full System 4 routine.

Pros:

• Lightweight enough not to further flatten fine, thinning hair
• Color-safe, won't strip color-treated strands
• Peppermint/mint oils give a light cooling sensation on the scalp

Cons:

• Formulated to work as part of the full System 4 three-step regimen — claims apply to the whole routine, not this conditioner alone
• Contains parabens, which some consumers specifically avoid
• Mint/menthol-type ingredients can be noticeable enough that very sensitive scalps may find them tingly