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When it comes to finding the right clarifying shampoo, two stand out above the rest: Ouai Detox Shampoo and the K18 Peptide Prep Detox Shampoo. While both are marketed as “detox,” and promise to remove buildup without drying out your hair, they’re actually formulated pretty differently, and you notice those key differences when you use them, too.

The Ouai Detox Shampoo is much more straightforward, especially if you’ve used clarifying shampoos before. It focuses on giving your scalp a true refresh, leaving you with a deep-clean, fresh feeling. The other, K18 Peptide Prep Detox Shampoo, focuses more on combating mineral build-up and prepping the hair a la gentle spa refresh.

Both perform well and are worth the money in my opinion; these are definitely my top 2 clarifying shampoos out of all that I’ve tried. That said, depending on your hair type, water quality, and how often you clarify, there’s a clear winner that will help give you a healthy, balanced scalp (and hair).

Breaking down ingredients, formulation, price, and more, here’s exactly how they compare — and which one is best for you.

ouai detox shampoo vs k18 peptide prep detox shampoo

ouai detox shampoo

One of my favorites, the Ouai Detox Shampoo is safe for all hair types and textures. It contains chelating agents as well as apple cider vinegar. Together, these ingredients work to

remove hard water deposits and impurities while also exfoliating the scalp, removing flakes, residue, and buildup. Your hair feels noticeably cleaner and shinier after using this, and what makes it stand out to me is that your hair feels smoother and shinier. Oftentimes, clarifying shampoos can cause dryness, which accentuates frizz, but your hair feels polished yet clean after using the Ouai Detox Shampoo.

The scent is mild. Many Ouai products have floral notes, and while this does as well, I consider the scent to be very neutral and clean; even my boyfriend loves it, and he’s picky about fragrance.

Gentle enough to use weekly, the Ouai Detox Shampoo is cruelty-free, gluten-free, and free of sulfates SLS and SLES, parabens, phthalates, and mineral oil.

pros

Gentle yet effective; gives your hair and scalp a deep clean
True gel-like texture that lathers easily
Doesn’t dry out your hair
For all hair textures - fine, medium, thick
For all hair types - straight, wavy, curly, coily
Adds shine
Makes your hair soft
Reduces frizz

cons

If used without conditioner afterwards, can cause tangles
Using too frequently can dry out or damage hair
Scent is subtle, but you can slightly notice hints of apple cider vinegar

k18 peptide prep detox shampoo

K18 is a prestige haircare brand known for highly-concentrated, science-backed formulas that prioritize hair and scalp health. They frequently incorporate peptides into their haircare products, meant to offer protection that reduces damage and restores hair health

The K18 Peptide Prep Detox Shampoo is no different. It contains the signature K18 Peptide that works as a protective shield to reduce protein loss that can weaken hair to keep it feeling soft, strong, healthy, and clean. That said, this is a detox shampoo, so it’s designed to clarify the hair, not repair it.

It’s also infused with activated charcoal to absorbs toxins, excess oils, and dirt in the hair and scalp, as well as salicylic acid, which clears sebum buildup without stripping essential moisture and lipids.

What surprised me about the K18 Peptide Prep Detox Shampoo is that it’s a translucent dark green color (due to the activated charcoal). However, it’s still a color-safe formula that did not make my highlights brassy or orange, which I really appreciated it.

The formula is slightly thinner than the Ouai Detox Shampoo, but it’s still a traditional shampoo texture. More gel-like than creamy, it lathers easily and feels reminiscent of a spa-treatment in how it leaves your scalp feeling clean and refreshed, not stripped or dry.

The scent is the signature K18 scent - a light citrus that’s slightly earthy/ woody, but not overwhelming. It’s subtle, so even if you are sensitive to fragrance, you can use this shampoo.

pros

Extremely gentle formula that focuses on scalp health, but also cleanses the hair
pH balanced, non-stripping formula
Color-safe
Lightweight gel-like shampoo consistency (thinner than Ouai)
Lathers without stripping the hair
Doesn’t dry out hair
For all hair textures - fine, medium, thick
For all hair types - straight, wavy, curly, coily
Vegan
Light citrus scent

cons

More expensive than the Ouai Detox Shampoo by $5 per bottle (comes out to $1.19 per ounce)
Using too frequently can dry out or damage hair
Contains salicylic which can be drying or irritating to some

which is best: ouai detox shampoo vs k18 peptide prep detox shampoo?

price

If you’ve visited my website before, you know I love breaking down the price per ounce because while I’m not opposed to investing in good haircare, I want to make sure the product is truly valuable. That said, here’s the pricing breakdown of the Ouai Detox Shampoo vs K18 Peptide Prep Detox Shampoo:

Ouai Detox Shampoo retails for $34 for a 10oz bottle, making it $3.40 per ounce
K18 Peptide Prep Detox Shampoo retails for $39 for an 8.5oz bottle, making it $4.59 per ounce

As such, when you purely look at cost per ounce, Ouai Detox Shampoo is cheaper and the better deal.

Going off of personal experience, I use a clarifying shampoo and have used full bottles of each. I find Ouai to still be the better deal. I need a teensy bit more of the K18 Peptide Prep Detox Shampoo to get a good lather, and while it’s a gentler formula meant for color-safe hair, the results of both are so similar that I prefer Ouai Detox Shampoo. It frees up my budget a little to then invest in leave-in conditioning treatments like the K18 Leave-In Molecular Repair Hair Mask.

That said, if you have all-over bleach or an extremely sensitive scalp, you’ll probably prefer to spend the few extra dollars for the K18 Peptide Prep Detox Shampoo since it’s a gentler formula all-around.

Also gentle enough to use weekly, the K18 Peptide Prep Detox Shampoo is vegan, gluten-free, and cruelty-free. It’s also free of sulfates SLS and SLES, parabens, phthalates, and mineral oil.

formulas and ingredients

Both are gel-like formulas; the K18 Peptide Prep Detox Shampoo is slightly thinner, though they both lather well. I think choosing between the two comes down to two key ingredients: ACV for Ouai, salicylic acid for K18. My fine hair personally responds better to ACV, and I think it’s more universal for all hair types. I'd truly side-eye any other shampoo that contains salicylic acid except for K18, because they’re so science-backed and you can trust that they’re not overdoing it, which would cause dryness and scalp irritation.

Both are formulated to be color-safe, so it comes down to how you want your hair (and scalp) to feel. For a gentle cleanse, get K18 Peptide Prep Detox Shampoo. For a true deep clean and refresh, get Ouai Detox Shampoo.

which is stronger?

Ouai Detox Shampoo is stronger. It lathers a little better, has a true gel-like consistency, and leaves your hair feeling truly deep-cleaned and refreshed. It’s strong, but not stripping, thankfully, so your hair will also feel soft and shiny afterwards.

which removes hard water better?

If you have just hard water build-up, you’ll love how gentle yet effective K18 Peptide Prep Detox Shampoo is. If you also need to remove styling product-build up (especially if they contain silicones), you are going to get a better cleanse using Ouai Detox Shampoo.

Overall, I wouldn’t say one is particularly better than the other. I notice hard water build-up especially after I travel, as hotel water can wreak havoc on my hair. I’ve used both shampoos post-travel, and my scalp feels truly clean and refreshed after both.

is one more stripping?

Not really. I honestly find both clarifying shampoos to be some of the least drying available. That said, if I had to point my finger at one, I’d say that the Ouai Detox Shampoo is slightly more stripping because it contains ACV. However, both are sulfate-free and formulated with care, so you don’t have to worry about either leaving your hair dried out and feeling like straw as other clarifying shampoos can do.

cleansing power: which removes more buildup?

Overall, the Ouai Detox Shampoo removes more build-up, though both work really well. That said, let’s get a little more nuanced here.

For oil or hard water mineral build-up concentrated around your scalp (especially if you swim a lot), the K18 is going to most effectively cleanse your hair without drying it out.

If you use lots of styling products (especially with silicones), have excess oil, or work out regularly, you’ll get a deeper clean with the Ouai Detox Shampoo.

does either feel drying?

Neither feels drying. Whether you have fine, color-treated, or high-porosity hair, both the Ouai Detox Shampoo and K18 are gentle enough to give you a deep clean without drying your hair. That said, if you are prone to frizz, get Ouai Detox Shampoo as it feels a little more conditioning and tames frizz.

Whichever clarifying shampoo you choose, make sure to follow-up with a nourishing conditioner or hair mask.

how often should you use each?

A good rule of thumb is to use a detox or clarifying shampoo every week to 10 washes, depending on your hair type. “Too much of a good thing” applies, though, so you want to make sure you’re not overdoing it. Thick hair (as well as color-treated hair) should push closer to 2-3 weeks, but if you have fine or oily hair, weekly is a great guideline to follow.

I have a full guide on How Often to Use Clarifying Shampoo depending on your hair type and lifestyle (regularly working out, if you have color-treated hair, etc.) that may be worth checking out.

best for fine hair vs thick hair

This is less about your hair type and more about the results you want, because both shampoos are formulated for all hair types - which I have tested and verified. I have fine hair, my mom has thick hair, and we both love each. I’ve also had my boyfriend test them; his hair is medium, but short, so we’ve really gotten to see how well these shampoos work for all hair types. Ultimately:

If you want a lightweight reset, get K18 Peptide Prep Detox Shampoo.

If you want a deep clean, get Ouai Detox Shampoo.

best for color-treated hair

For color-treated hair, the best clarifying shampoo is the K18.

That said, the Ouai Detox Shampoo is also color-safe, so if you’re dealing with a lot of product build-up or have an oily scalp, you may prefer the Ouai Detox Shampoo. My rule: unless you have all-over bleach, a fantasy color, or a high-maintenance color, pick your (color-safe) clarifying shampoo based on oiliness and product build-up. Unless you’re addressing that first, your color will still look dull.

best for sensitive scalps

This is two-fold. Your scalp is still part of your skin, so if you are generally sensitive to salicylic acid, avoid K18 and get the Ouai Detox Shampoo. That said, if you can handle salicylic acid, I think the K18 is overall better for sensitive scalps. I have dry, sensitive skin and can use either shampoo without issue.

best for product build-up

When it comes to product-buildup, the Ouai Detox Shampoo is the winner. Whether your build-up comes from hair products, hard water, or working out daily, the Ouai Detox Shampoo gets it all without stripping your hair. It also leaves your hair smooth and shiny, whereas a lot of other clarifying shampoos are drying and accentuate frizz. That’s not to say that the K18 shampoo doesn’t get product build-up; I just think Ouai does a better job.

FAQ

is k18 peptide prep detox shampoo stronger than ouai?

No. While I do think that the salicylic acid can be too strong on the scalp for some, I find the ACV component of Ouai Detox Shampoo makes it a stronger shampoo overall. You get a better lather and deeper clean, but it’s not drying at all.

is ouai detox shampoo good for hard water?

Yes, the Ouai Detox Shampoo is formulated with chelating agents that help remove hard water deposits and impurities.

can you use k18 peptide prep detox shampoo on color-treated hair?

Yes! K18 Peptide Prep Detox Shampoo is specifically formulated to be color-safe. In my experience, it doesn’t make my highlights dull or brassy, whereas other detox shampoos can.