Ingredient review
Isopropyl 3-Methylthiobutyrate
INCI: ISOPROPYL 3-METHYLTHIOBUTYRATE
A synthetic fragrance ingredient that adds a fruity note but offers no skincare benefit; safe at low levels but may cause sensitivity in some individuals.
In plain English
Isopropyl 3-Methylthiobutyrate is a man-made chemical used to give products a fruity, sometimes slightly sulfurous smell. It doesn't moisturize, protect, or treat the skin—it's purely there for scent. Because it's used in tiny amounts, it's generally considered safe, but like any fragrance ingredient, it can occasionally cause irritation or allergic reactions in sensitive people.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Isopropyl 3-Methylthiobutyrate is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Isopropyl 3-Methylthiobutyrate.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A synthetic ester compound used as a fragrance ingredient in cosmetics and personal care products. It is not derived from natural sources and is added solely for its odor.
How it works
It evaporates from the skin's surface, releasing a fruity aroma that masks or enhances the product's scent. It has no active effect on the skin's structure or function.
Pros
Pleasant scent
Adds a fruity, appealing aroma that can make the product more enjoyable to use.
Low irritation risk
At typical low concentrations, it rarely causes irritation for most people.
Cons and cautions
No skincare benefit
This ingredient does not hydrate, soothe, or improve skin health—it's purely for fragrance.
Potential allergen
Like many fragrance ingredients, it can trigger allergic reactions or sensitivity in some users, especially with repeated use.
Best for
- Anyone who enjoys scented skincare and has no known fragrance allergies
- People looking for a fruity scent in their routine
Use caution if
- Individuals with fragrance allergies or very sensitive skin
- Those who prefer fragrance-free products
Usage tips
Safety summary
Isopropyl 3-Methylthiobutyrate is considered safe for use in cosmetics at low concentrations. It is not a common irritant or sensitizer, but individuals with fragrance allergies should exercise caution.
Research notes
Limited peer-reviewed research specifically on this ingredient; safety is inferred from general fragrance ingredient assessments by bodies like IFRA and the Research Institute for Fragrance Materials (RIFM).
Common label clues
- Typical concentration
- Very low, typically less than 1% in finished products
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions, subject to concentration limits and labeling requirements for allergens.
- Common uses
- Fragranced skincare, Body care, Hair care
- Environmental note
- As a synthetic compound, its environmental impact depends on production methods and disposal; it is not biodegradable in all conditions.
Good to know
- Fragrance ingredients like this one are often listed simply as 'fragrance' or 'parfum' on labels, so you may not see the specific name.
- The International Fragrance Association (IFRA) sets safety standards for its use.
Common questions
What is Isopropyl 3-Methylthiobutyrate in beauty products?
Isopropyl 3-Methylthiobutyrate is a man-made chemical used to give products a fruity, sometimes slightly sulfurous smell. It doesn't moisturize, protect, or treat the skin—it's purely there for scent. Because it's used in tiny amounts, it's generally considered safe, but like any fragrance ingredient, it can occasionally cause irritation or allergic reactions in sensitive people.
What does Isopropyl 3-Methylthiobutyrate do in a beauty product?
It evaporates from the skin's surface, releasing a fruity aroma that masks or enhances the product's scent. It has no active effect on the skin's structure or function.
Is Isopropyl 3-Methylthiobutyrate safe for most people?
Isopropyl 3-Methylthiobutyrate is considered safe for use in cosmetics at low concentrations. It is not a common irritant or sensitizer, but individuals with fragrance allergies should exercise caution.
Who should be careful with Isopropyl 3-Methylthiobutyrate?
Individuals with fragrance allergies or very sensitive skin Those who prefer fragrance-free products
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.