The Review
Olaplex No.4P Blonde Enhancer Toning Shampoo Review
A full review of Olaplex No.4P: the bond building active inside a toning shampoo, the 1 to 3 minute published timing, sulfate free credentials and the small bottle trade off.
How this review was made: from the manufacturer's published formula and specifications, the live Amazon listing, and recurring themes in owner commentary. Eclat Press does not claim hands-on testing it has not done, and publishes no scores.
A bond active inside a toner
The published ingredient list for No.4P includes Bis-Aminopropyl Diglycol Dimaleate, the patented active the whole Olaplex system is built on, in a base of glycerin and gentle co-surfactants beside the Acid Violet 43 pigment. The brand describes the shampoo as ultra-concentrated and positions it as cleansing and toning from roots to ends. In cosmetic terms, the promise a buyer should hold it to is hair that looks brighter and feels softer and stronger after the wash, and the formula architecture is genuinely different from a pigment only rival like the Fanola.
Timing and texture in use
The directions are unusually complete: distribute evenly between the palms first, apply to wet hair, lather fully, leave 1 to 3 minutes, rinse well, and extend to 5 minutes only for more intense toning, weekly or as needed. The palms first step matters more than it reads, because a concentrated violet shampoo applied in one spot will tone that spot hardest. The listing notes the formula as sulfate free, paraben free and formaldehyde free in its materials notes, and as vegan in its special features, which places it at the gentle end of this category's chemistry.
What owners report
Owners praise brightness after a single wash, softness unusual in a toning shampoo, and how little of the concentrated formula a full head needs. The recurring complaints are about the container and the calendar rather than the colour work: the 250 ml bottle empties quickly when a household shares it, and hair used to a gentler rhythm can feel dry when the shampoo is used more often than its weekly direction. A smaller group with very porous hair reports violet lingering after the long sitting, the standard caution of this whole category.
No.4P is the thinking buyer's purple shampoo: a concentrated violet formula that carries the brand's patented bond building active into the one wash lightened hair cannot skip, with published timing of 1 to 3 minutes and a sulfate free, vegan listed profile.
From the verdict
In Owners' Hands
Recurring themes, in aggregate and without numbers we cannot stand behind.
What owners praise
- Blonde and grey hair looks brighter after one wash is the recurring theme
- Hair feels softer rather than squeaky after a toning wash, owners report
- The concentrated lather means a small amount covers long hair
What owners question
- Purple can linger on very porous or damaged sections if the longer time is used
- Some owners find it drying when used more often than weekly
- The bottle empties quickly in households sharing it
Consider Instead
Kerastase Blond Absolu Bain Ultra-Violet Purple Shampoo
The prestige alternative, with a broader blue and violet pigment blend and a care formula built on hyaluronic acid instead of a bond active.
amika Bust Your Brass Cool Blonde Strength Repair Shampoo
A richer, butter carrying toning wash for dry blonde and silver hair that found No.4P too lean, with quinoa protein in place of the bond active.
Questions, Answered
Can No.4P be my only shampoo?
Its directions say weekly or as needed, which makes it the toning slot in a routine rather than the whole routine. Pair it with a gentle non toning shampoo for other wash days, and follow with the conditioner step your hair normally needs, since toning and conditioning remain separate jobs.
Does No.4P work on natural grey hair?
Yes, grey hair is named in its published brief, for natural and colour treated hair alike. Grey hair tends to be porous, so use the 1 to 3 minute standard window rather than the extended sitting, and distribute the shampoo between the palms first as the directions specify, for an even deposit.
Keep Researching
Every page in the Purple and Blue Shampoos edit.
- 01Purple and Blue Shampoos: the hubHub
- 02Best Purple and Blue Shampoos 2027Best of
- 03Purple vs Blue Shampoo: Which Hair Colours Each One Is ForGuide
- 04How Often to Use Toning Shampoo, and How Long to Leave It OnGuide
- 05Toning Shampoo Mistakes: Brassiness Returning, Lilac Casts and DrynessGuide
- 06Kerastase Blond Absolu Bain Ultra-Violet Purple Shampoo ReviewReview
- 07Fanola No Yellow Purple Shampoo ReviewReview
- 08Kerastase Bain Ultra-Violet vs Fanola No YellowComparison
- 09Matrix Brass Off vs Fanola Wonder No OrangeComparison
- 10Purple and Blue Shampoos Buying GuideBuying guide
- 11Toning Shampoo Care and Keeping: Fixes for Lilac Casts, Dryness and Tone That Will Not HoldCare
More from the Premium Hair Desk
Premium Hair
Bond Repair and Hair Treatments
Bond repair treatments sorted by technology, format and the damage pattern they actually suit
Read the edit
Premium Hair
Clarifying and Sulfate-Free Shampoos
Two different wash jobs, kept separate: deep cleansing clarifiers for build-up days, and gentle sulfate-free shampoos for every other day
Read the edit
Premium Hair
Dry Shampoos
Premium dry shampoos judged on absorbency, residue on dark hair and how honestly each one bridges wash days.
Read the edit
Disclosure: links on this page are affiliate links. As an Amazon Associate, Eclat Press earns from qualifying purchases, at no added cost to you. Rankings are never sold. See our affiliate disclosure and methodology.