A beauty editor's honest Olaplex No.4P Purple Shampoo review—does it live up to the hype?

There is a lot of hype around this brand on TikTok, and one of the newer additions to the lineup, Olaplex No.4P Blonde Enhancer Toning Shampoo, is no exception. Our collective obsession with the best Olaplex products started out with the two initial in-salon treatments—the first is mixed into your hair color, the second is the equivalent of a professional-strength deep conditioning mask and is applied at the backwash. 

Both are scientifically proven to prevent the disulfide bonds in your hair from breaking during the coloring process by effectively ‘gluing’ them together. Olaplex also prevents any protein-destroying molecules from ravaging your strands by stepping in before they have the chance to wreak havoc. In short, they're perfect for those who frequently bleach or dye their hair.

Since the initial launch almost 10 years ago, the line now comprises a whopping 15 different products, including No.4D Dry Shampoo and even a lash serum. Their functions vary but all are powered, to some degree, by the same hero ingredient as the salon treatments. This patented molecule actually improves the hair's structure—rather than just papering over the cracks—a claim that most haircare brands simply cannot make. So how does the newbie, designed for highlighted, gray, or natural blonde hair, fare? Ahead, a beauty editor shares her in-depth review. 

Meet the tester

Meet the tester

Fiona Embleton

Up until age 16, I was like a beacon for lost Scandinavian tourists on the subway, who’d launch into a friendly Swedish welcome having clocked my natural platinum strands. But as the years passed, my hair gradually became a little darker and duller, eventually straying into "mousy" territory—neither blonde nor brown, but some dishwater hue in between. I missed my natural shade and positively hated having a hair color with this name.

Ever since, I’ve religiously highlighted my hair every three months. Few feelings beat stepping out of a salon root-free, but it can be short-lived if you live is in a hard-water area (like me). Minerals and metals penetrate blonde hair, which tends to be more porous, and warm tones creep in. I’m already a big fan of Olaplex, as the in-salon treatments have resuscitated my bleached strands, while Olaplex No.3 Hair Protector has been a part of my weekly regime for years—so, naturally, I was intrigued by the No4.P Shampoo.

A beauty editor's honest review of Olaplex No.4P Blonde Enhancer Toning Shampoo

Ingredients—What's in the Olaplex No.4P Purple Shampoo?

As for the newer shampoo, Olaplex No.4P Blonde Enhancer Toning Shampoo is a customizable purple formula with highly concentrated pigments—so you can dial up the toning depending on how brassy your hair is. To quickly recap color theory and how the best purple shampoos work, purple sits across from yellow on the color wheel, which is why this type of shampoo is so effective at neutralizing brassy tones. 

According to clinical trials, hair looks three times brighter after just one use of the Olaplex No.4P compared to other top purple shampoos in the market. But what really sets this particular purple shampoo apart from competitors is that it also contains Olaplex’s patented molecule, bis-aminopropyl diglycol dimaleate. Put simply, this high-tech molecule rebuilds the broken bonds in the hair that result from heat styling, chemical treatments, and (this is a key one in blonde hair) bleaching. You can read more about its benefits in our guide on using Olaplex as a treatment. 

Admittedly, the levels of this particular ingredient aren’t as high in this formula as in the salon-only treatments—but every little helps when you consider that the oxygen molecules in peroxide attach themselves to bonds and deplete the hair's protein, leaving it brittle. What's more, like all Olaplex products, No. 4P Shampoo is both vegan and cruelty-free, as well as containing no formaldehyde, sulfates, parabens, phosphates, or phthalates. 

Application—How to use the Olaplex No.4P Purple Shampoo

To achieve optimum results from this brightening shampoo, you should follow the instructions on the bottle. It’s also important to do a patch test inside your elbow or behind your ear and wait 48 hours to ensure there's no irritation.

• Step 1 (optional): Pre-wash with No.4 bond Maintenance Shampoo to remove product build-up.
• Step 2: Apply No. 4P Blonde Enhancer Toning Shampoo to wet hair. Lather and leave to process for one to three minutes. For more intense toning, leave on hair for up to five minutes. Use two to three times a week or as often as needed.
• Step 3: Rinse fully. Follow with No.5 Bond Maintenance Conditioner, or No.8 Bond Intense Moisture Mask for extra hydration.

The verdict—Is Olaplex No.4P Purple Shampoo worth it?

Like most bottle blondes, I’ve tried my fair share of purple shampoos to brighten my highlights between salon visits. While those deep amethyst-hued shampoos certainly nix brassiness, they also suck the moisture from my strands, leaving them the same shade and texture as straw. Daily lilac shampoos, on the other hand, are too watered-down, making very little difference to the overall result. However, this wasn't the case with Olaplex's offering. 

The first thing to note is that my hair looked and felt salon-fresh after using it. The tone is customizable, so I only left it on recently-dyed hair for a maximum of three minutes once a week. After six weeks, I upped the toning time to five minutes, twice a week. It’s also sulfate-free, so the formula isn’t harsh on strands or on the scalp—which is important, given what your roots go through in the colorist’s chair. Regardless, my hair never felt parched and, crucially, I was putting goodness back into strands post-color courtesy of Olaplex’s infamous bond-repairing molecule. I also think would also work well in an Olaplex routine for curly hair that's been bleached blonde and needs cooling. 

I also love that you can slot this shampoo into your usual hair care routine. You don’t have to buy a separate conditioner to create a de-brassing "system", you simply follow with your usual No.5 Bond Maintenance Conditioner. Of course, you could use another conditioner if you wish, but I find products from the same brand tend to work in synergy; with Olaplex, this is all the more important, given its unique molecule.

For me, the luminous shine and multi-dimensional tones my hair is left with are a testament to that. The cherry on top, though? The purple shade doesn’t stain your hands or your shower curtain.