Obagi C5 Serum
Obagi

Obagi C5 Serum

オバジ C5セラム
skincare serum

Product Description

The entry level serum in Rohto's Obagi C vitamin C series, containing 5% pure ascorbic acid plus vitamin E. Part of a concentration ladder that goes C5, C10, C20, and C25, with each step increasing both potency and price. The C5 is the gentlest in the range, making it a good starting point for people new to pure vitamin C or those with sensitive skin who can't tolerate higher concentrations. Targets pore refinement, dullness, and uneven skin tone. A perennial award winner in Japan and one of the most popular vitamin C serums sold in Japanese drugstores, often recommended as a souvenir purchase by beauty tourists. Applied after toner, a few drops patted across the face. Note that Rohto's Obagi line is a Japan exclusive brand, separate from the US Obagi Medical line.

What's in It

Ascorbic Acid Tocopherol

FAQ

Should I start with C5, C10, or C20?
Start with C5 if you're new to pure vitamin C or have sensitive skin. The 5% ascorbic acid is gentle enough to test tolerance without risking irritation. If your skin handles it well after a few weeks, you can step up to C10 or C20. Most people find C10 hits the sweet spot between efficacy and gentleness.
Is Rohto's Obagi the same as Obagi Medical in the US?
No. They're completely separate brands. Rohto's Obagi is a Japan-exclusive drugstore line with a focus on vitamin C serums and is widely available in Japanese pharmacies. Obagi Medical is a US dermatologist brand sold at higher price points. They share a name but have different formulations, philosophies, and ownership.
Does vitamin C serum oxidize quickly?
Pure ascorbic acid is unstable and will oxidize when exposed to light, air, and heat. The Obagi C serums come in dark bottles to slow this down. Store it in a cool, dark place and close the cap tightly after each use. If the serum turns dark yellow or brown, it's oxidized and should be replaced. Fresh serum is pale yellow to clear.

Learn More

Brand Guide Melano CC vs Obagi C25 vs Skinceuticals CE Ferulic: Vitamin C Compared Brand Guide Obagi Japan vs Obagi Medical: C5, C10, C20 & C25 Guide (2026) Buying Guide Best Japanese Ceramide Skincare Products for Barrier Repair Buying Guide Best Japanese Anti Aging Skincare: Products That Deliver Results

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