Ingredient review

Isopropyl 3-Methylthiocrotonate

INCI: ISOPROPYL 3-METHYLTHIOCROTONATE

A synthetic fragrance compound that adds unique sulfurous notes to products; generally safe at low concentrations but offers no skincare benefit.

beautyskincarefragrance

In plain English

This is a man-made chemical added to cosmetics solely for its smell. It creates a distinctive scent that can be fruity, roasted, or slightly sulfurous (like cooked onion or garlic). It doesn't moisturize, treat, or improve skin in any way—it's just there for fragrance.

Review score

Safety, usefulness, and evidence

3.5Good
3.5/ 5

Potentially useful with some tradeoffs

The evidence base is still emerging, so marketing claims deserve extra caution.

Risk flags are low for most users, though the finished product can still irritate.

Source
synthetic
Evidence
emerging
Irritation
low
Clogging risk
low
How reviews are scored

Quick decision guide

Useful, but context matters

Isopropyl 3-Methylthiocrotonate 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.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Isopropyl 3-Methylthiocrotonate.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. 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

low

Less likely to sting, burn, or bother most users, though sensitive skin can still react.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

emerging

The ingredient may be promising, but claims should be treated more cautiously.

What it is

A synthetic organic compound from the thioester family, used as a fragrance ingredient in cosmetics and personal care products.

How it works

It evaporates from the product's surface and interacts with olfactory receptors in the nose, creating a specific scent perception. It has no known functional effect on the skin itself.

Pros

Unique Scent Profile

Adds a distinctive, complex note (fruity, roasted, sulfurous) that can make a product's fragrance stand out.

Low Use Level

Effective at very small amounts, which helps keep overall irritation potential low for most users.

Cons and cautions

No Skincare Function

This ingredient does not hydrate, protect, or improve skin—it only provides scent, so it adds no value for skincare goals.

Potential Allergen

As a synthetic fragrance, it can trigger contact dermatitis or allergic reactions in sensitive individuals, especially with repeated use.

Best for

  • Anyone who enjoys fragranced products and does not have a known sensitivity to synthetic fragrances.
  • Consumers looking for unique or gourmand scent profiles in their body care.

Use caution if

  • Individuals with fragrance allergies or sensitive skin who prefer fragrance-free products.

Usage tips

If you have sensitive skin, patch test any product containing this ingredient before full application.
Look for products that list fragrance ingredients separately if you want to avoid specific aroma chemicals.

Safety summary

Considered safe for use in cosmetics at the low concentrations typical for fragrance ingredients. However, like all fragrance components, it may cause allergic reactions in susceptible individuals.

Research notes

There is limited published research specifically on Isopropyl 3-Methylthiocrotonate. Safety assessments rely on general fragrance ingredient guidelines and analogy to similar thioesters.

Common label clues

Typical concentration
Typically used at very low levels (below 1%) as a fragrance component.
Regulatory status
Approved for use in cosmetics in the EU and US at low concentrations as a fragrance ingredient, subject to IFRA guidelines.
Common uses
Fragranced products, Perfumes, Body washes, Lotions
Environmental note
As a synthetic compound, its environmental persistence and bioaccumulation potential are not well-documented; limited data available.

Good to know

  • This ingredient is not a common standalone label; it's typically part of a fragrance blend and may appear low on the ingredient list.
  • Regulatory bodies like IFRA (International Fragrance Association) set usage limits for fragrance ingredients to ensure safety.

Common questions

What is Isopropyl 3-Methylthiocrotonate in beauty products?

This is a man-made chemical added to cosmetics solely for its smell. It creates a distinctive scent that can be fruity, roasted, or slightly sulfurous (like cooked onion or garlic). It doesn't moisturize, treat, or improve skin in any way—it's just there for fragrance.

What does Isopropyl 3-Methylthiocrotonate do in a beauty product?

It evaporates from the product's surface and interacts with olfactory receptors in the nose, creating a specific scent perception. It has no known functional effect on the skin itself.

Is Isopropyl 3-Methylthiocrotonate safe for most people?

Considered safe for use in cosmetics at the low concentrations typical for fragrance ingredients. However, like all fragrance components, it may cause allergic reactions in susceptible individuals.

Who should be careful with Isopropyl 3-Methylthiocrotonate?

Individuals with fragrance allergies or sensitive skin who prefer fragrance-free products.

Research sources

The Good Scents Company - Isopropyl 3-MethylthiocrotonateOpenIFRA Standards - Fragrance SafetyOpenCosIng Database - European CommissionOpen

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.