People with bleached, colored, relaxed, or otherwise chemically processed hair who are also noticing light thinning and want a conditioner formulated for that specific combination, rather than a plain moisturizing conditioner. It was designed to pair with Nioxin's System 5 shampoo and scalp treatment as a 3-step regimen. Note: Nioxin has discontinued the numbered System 5/6 line and now directs these customers to its System 3 conditioner instead.

The logic behind System 5 (and its replacement, System 3) is that chemically treated hair needs a different conditioning approach than natural hair with light thinning, since the cuticle has already been altered by bleach or chemical processing. The conditioner is formulated to restore moisture balance and manageability without adding heavy silicones that can flatten fine, thinning hair further, and it's meant to be used as part of a matched routine rather than swapped in for a different conditioner.

1. After shampooing with a matching cleanser, apply the conditioner from scalp to ends, leave on for one to three minutes, then rinse thoroughly.
2. Follow with the corresponding leave-in scalp treatment as the third step of the routine.

A few things are worth weighing given this product's current status.

Pros:

• Purpose-built for chemically treated hair, which typically needs more conditioning support than virgin hair
• Marketed with a named moisture-balancing technology (Smooth Plex) rather than generic conditioning claims
• Designed to be layered with a matching shampoo and scalp treatment for a coordinated routine

Cons:

• Nioxin discontinued System 5 when it moved from six numbered systems to four, and now directs former System 5 customers to System 3 — buyers may be purchasing a formula the brand no longer actively markets
• As a rinse-out conditioner within a scalp-care system, it's a supporting product, not a standalone thinning-hair treatment
• Matching System 5 shampoo and scalp treatment may be harder to find now that Nioxin's current marketing has moved to the System 3 name