Ingredient guide
4-Methoxysalicylic Acid (4-MSA)
4-methoxysalicylic acid
In short
4‑Methoxysalicylic Acid (4‑MSA/4‑MSK) is a brightening ingredient developed to target pigment formation more selectively. It’s often used to help skin look more even-toned.
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What it is
Shiseido-developed tyrosinase inhibitor; salicylic acid backbone with methoxy group enhances melanocyte specificity.
When to use it
Evenings. Exfoliating acids sit best away from daylight hours.
A couple of nights a week to start.
Where it sits
An evening treatment step. After cleansing, before the heavier layers go on.
- Cleanse
- 4-Methoxysalicylic Acid
- Hydrate
- Moisturise
Also found as
Related
Where to find it
Options across the range, not a ranking. Run one through Lens and MIRU will tell you if it fits you.
Shiseido White Lucent MicroSpot Serum
Shiseido White Lucent Brightening Gel Cream
Fit comes first: the Lens checks each product against your skin before any retailer link. We may earn a commission, at no cost to you. Picks are editorial, never paid.
Common questions
What does 4‑Methoxysalicylic Acid do for skin?
It focuses on reducing the appearance of uneven pigmentation by slowing melanin formation in the skin’s upper layers.
Is 4‑MSA suitable for sensitive or combination skin?
It is generally considered gentle and is often paired with soothing ingredients, making it a fit for sensitive and combination skin types.
How is 4‑MSA used in skincare?
You’ll usually find it in brightening serums or emulsions designed for overall tone improvement.
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Personal guidance, not medical advice.