No. 5+ Glutathione C Facial Spa Cleanser

Most cleansing oils have one job — dissolve the day and get out of the way. Numbuzin's No. 5+ Glutathione C Facial Spa Cleanser has grander ambitions. It wants those sixty seconds of massage time to count for something beyond just removing your sunscreen. Whether it fully delivers on that promise requires a conversation about contact time, but the attempt itself is worth examining.

Numberzin's entire brand identity revolves around a numbered system where each digit corresponds to a skin concern. Number five is their brightening line, and glutathione is its centerpiece. In Korea, glutathione has achieved near-mythical status as a brightening ingredient — it's the active behind countless "glass skin" claims and a staple in aesthetic clinics across Seoul. Putting it in a cleansing oil is a way of saying the brightening mission starts before your toner even touches your face.

The formula builds its brightening strategy on three distinct pathways. Glutathione inhibits tyrosinase, the enzyme that kickstarts melanin production. Ascorbic acid (vitamin C) provides antioxidant support and its own melanin-suppressing activity. Niacinamide takes a different route entirely, blocking the transfer of melanosomes to skin cells. Three ingredients, three mechanisms — it's not redundant stacking, it's strategic layering. The inclusion of hydroxypropyl cyclodextrin is a thoughtful touch, as it helps solubilize the water-soluble vitamin C within the oil base.

Now for the honest part: these actives are in a wash-off product. You're massaging this into your skin for maybe ninety seconds before rinsing it down the drain. The research on topical glutathione is still developing — a 2019 systematic review found limited clinical trials, and the evidence that does exist involves leave-on formulations applied consistently over weeks. Expecting dramatic brightening from a cleanser alone would be optimistic. What you can reasonably expect is some antioxidant benefit during the massage and a foundation-setting step that complements the rest of your brightening routine.

The oil base itself is genuinely lovely. Jojoba seed oil, sunflower seed oil, and olive oil form the cleansing backbone — a trio that dissolves makeup efficiently while leaving skin feeling nourished rather than stripped. Sea buckthorn fruit oil adds its characteristic orange-gold tint and contributes carotenoids and omega-7 fatty acids. The formula emulsifies cleanly when you add water, turning milky white and rinsing without that frustrating oily film some cleansing oils leave behind.

Then there's the sensory experience, which is where this product earns its "spa" designation. The blend of lavender, cedarwood, lemon peel, mandarin, and rosemary essential oils creates a genuine aromatherapy moment. It smells like an upscale facial, not like a drugstore cleanser. The scent lingers briefly after rinsing — a pleasant trail of lavender and wood that signals the transition from daytime to evening skincare ritual.

But those essential oils are also this product's most significant limitation. Lavender oil, lemon peel oil, and the citrus oils contain compounds like limonene, citral, and geraniol that are well-documented contact allergens. If your skin is sensitive or reactive, this cleanser's most appealing feature becomes its biggest drawback. The aromatherapy experience that makes it feel special is the same thing that makes it unsuitable for a significant portion of skincare consumers.

The texture during application is smooth and substantial without being overly thick. Two to three pumps covers the face comfortably. The massage feels genuinely pleasant — the oil has enough slip to glide without tugging, and you can feel it working through stubborn makeup. Waterproof mascara dissolves within twenty to thirty seconds of gentle circling. Some versions of the bottle come with a built-in roller massage cap, which adds a cooling, depuffing element to the cleansing step.

At $19.50 for 200ml, the pricing sits comfortably within K-beauty cleansing oil territory. It's not the cheapest option, but the formulation complexity justifies the price point. The inclusion of glutathione, vitamin C, and niacinamide — even in a wash-off format — represents more thoughtful formulation work than your average oil cleanser. A 300ml bottle is also available, offering better per-unit value for those who've already committed to the product.

The packaging is clean and modern, consistent with Numbuzin's minimalist aesthetic. The pump dispenser works reliably and dispenses the right amount without waste. It looks good enough to leave on your bathroom shelf without hiding it in a cabinet.

This cleanser works best as the first step in a double-cleanse routine. Follow it with a gentle water-based cleanser, and your skin is primed and clean without being compromised. It's particularly enjoyable as an evening wind-down ritual — the aromatherapy aspect genuinely helps mark the transition from the day's stress to nighttime self-care.

As a pure cleanser, it's very good. As a brightening treatment, temper your expectations — the actives are thoughtfully chosen but briefly present. The real value here is the combination of effective cleansing, pleasant sensory experience, and the knowledge that you're not just removing the day but setting the stage for everything that follows.

Formula

The Science

Glutathione, the headline active in this cleanser, is a tripeptide (L-cysteine, L-glutamic acid, and glycine) that functions as the body's primary endogenous antioxidant. Its relevance to skincare lies in its ability to inhibit tyrosinase — the rate-limiting enzyme in melanin biosynthesis — by chelating copper at the enzyme's active site. A 2017 review published in the Indian Journal of Dermatology, Venereology and Leprology examined the evidence for glutathione as a skin-lightening agent and found that while the mechanism is sound, clinical evidence was mixed, with most positive results coming from oral supplementation rather than topical application.

More recently, a systematic review published in the Journal of Clinical and Aesthetic Dermatology evaluated topical glutathione specifically and found that only five clinical trials met inclusion criteria, with a 2019 randomized controlled trial demonstrating that 2% oxidized glutathione lotion produced statistically significant melanin index reduction over 10 weeks of consistent application. Importantly, that study used a leave-on formulation — not a wash-off product like this cleanser.

The formula cleverly pairs glutathione with ascorbic acid and niacinamide, creating three distinct pathways of melanogenesis interference. Ascorbic acid reduces oxidized dopaquinone back to DOPA, interrupting the melanin synthesis cascade at a different point than glutathione's tyrosinase inhibition. Niacinamide, whose evidence base for brightening is more robust, works downstream by inhibiting melanosome transfer from melanocytes to keratinocytes — a mechanism validated in a study published in the British Journal of Dermatology (2002) showing a 35-68% inhibition of melanosome transfer with 5% niacinamide.

The inclusion of hydroxypropyl cyclodextrin is a formulation-savvy choice. Cyclodextrins form inclusion complexes with hydrophilic molecules, improving the solubility and stability of water-soluble actives like ascorbic acid within an oil-based medium. This addresses one of the fundamental challenges of putting vitamin C into a cleansing oil.

The practical limitation remains contact time. In a 60-90 second cleansing step, the penetration of these actives into the epidermis is minimal compared to leave-on formulations. The antioxidant benefit during application is real but modest, and this cleanser should be viewed as a complementary step rather than a standalone brightening treatment.

References

1. Glutathione as a skin whitening agent: Facts, myths, evidence and controversies — Indian Journal of Dermatology, Venereology and Leprology (2017)
2. Systematic Review of the Efficacy and Safety of Topical Glutathione in Dermatology — Journal of Clinical and Aesthetic Dermatology (2024)
3. The effect of niacinamide on reducing cutaneous pigmentation and suppression of melanosome transfer — British Journal of Dermatology (2002)

Dermatologist Perspective

Dermatologists generally view glutathione as a promising but still-evolving brightening ingredient with less robust clinical evidence than established options like hydroquinone, vitamin C, or niacinamide. Board-certified dermatologists note that while the mechanism of tyrosinase inhibition is well-understood, the delivery challenge in topical formulations — and especially in wash-off products — limits practical efficacy. That said, dermatologists who practice in Korea and other Asian markets have observed growing patient interest in glutathione-based products, and the combination with niacinamide and vitamin C in this formula aligns with evidence-based brightening strategies. For patients seeking a cleansing oil that offers some antioxidant benefit beyond basic cleansing, dermatologists may consider this a reasonable choice — provided the patient does not have essential oil sensitivity.

Guidance

Numbuzin's entire brand philosophy revolves around numbered solutions — each number targets a specific skin concern. No. 5 is their brightening line, built around glutathione, a tripeptide antioxidant that's become a Korean skincare obsession for its melanin-inhibiting properties. This cleansing oil extends that brightening philosophy to the very first step of a routine.

About Numbuzin Established Brand (5–20 years)

Numbuzin launched in 2019 under Korea's Benow Inc. and has rapidly gained international recognition for its numbered skincare system. The brand's formulations feature well-studied actives like glutathione and niacinamide, though independent clinical validation of its specific products remains limited compared to legacy K-beauty brands.

Brand founded: 2019 · Product launched: 2024

Myth vs. Reality

Myth

Glutathione in a wash-off cleanser can dramatically brighten skin on its own.

Reality

While glutathione is a potent antioxidant, its contact time in a cleanser is brief (typically 60-90 seconds). The brightening benefit from this product alone will be modest — it's best viewed as a complementary step within a full brightening routine that includes leave-on products.

Myth

Cleansing oils clog pores and cause breakouts.

Reality

When properly emulsified and rinsed (especially followed by a second cleanser), cleansing oils effectively dissolve sebum and oil-based impurities without clogging pores. This formula uses non-comedogenic jojoba and sunflower oils as its base.

FAQ

Common Praise

"Luxurious spa-like aromatherapy experience"

"Effectively removes waterproof makeup and sunscreen"

"Skin feels soft and glowy after use, not stripped"

"Beautiful packaging with built-in roller"

Common Complaints

"Essential oil scent may be too strong for some users"

"Brightening claims are hard to verify from a wash-off product"

"Can leave a slight residue requiring thorough second cleanse"

Appears In

best cleanser for dullness best cleansing oil for brightening best k beauty cleanser best cleanser for hyperpigmentation

Related Conditions

dullness hyperpigmentation dark spots

Related Ingredients

glutathione vitamin c niacinamide jojoba oil