Ingredient review
Trans-Trimethylundecadienal
INCI: TRANS-TRIMETHYLUNDECADIENAL
A synthetic fragrance compound that adds a fresh floral note but offers no skincare benefits and may be a concern for those sensitive to fragrance.
In plain English
This is a man-made chemical that smells like fresh flowers or citrus. It is added to products to make them smell nice, but it does not moisturize, treat, or improve your skin in any way. If you have sensitive skin or avoid fragrance, you may want to skip products containing this ingredient.
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
Trans-Trimethylundecadienal 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 Trans-Trimethylundecadienal.
- 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
Trans-Trimethylundecadienal is a synthetic aldehyde compound used exclusively as a fragrance ingredient. It is not derived from plants or natural sources but is created in a lab to produce a specific scent profile.
How it works
In a cosmetic product, it simply evaporates from the skin's surface, releasing a pleasant floral or citrus-like aroma. It has no active role in cleansing, moisturizing, or protecting the skin.
Pros
Pleasant scent
Adds a fresh, floral note that can make your skincare routine more enjoyable.
Low irritation for most
At typical low concentrations, it rarely causes irritation in people without fragrance sensitivities.
Cons and cautions
No skin benefit
This ingredient only provides scent—it does not hydrate, soothe, or improve skin health.
Potential allergen
Like many fragrance ingredients, it can cause allergic reactions or contact dermatitis in sensitive individuals.
Best for
- People who enjoy scented skincare and have no history of fragrance allergies
- Those looking for a fresh, floral scent in their routine
Use caution if
- Individuals with sensitive, reactive, or eczema-prone skin
- Anyone who prefers fragrance-free products
Usage tips
Safety summary
Generally considered safe for most people at the low concentrations used in cosmetics. However, it can cause allergic reactions in fragrance-sensitive individuals, and its use is regulated as a potential allergen in several regions.
Research notes
Limited peer-reviewed research specifically on trans-trimethylundecadienal. It is recognized as a fragrance allergen by the EU Scientific Committee on Consumer Safety (SCCS) and must be labeled when present above 0.001% in leave-on products.
Common label clues
- Typical concentration
- Typically used at very low levels (less than 0.1%) due to its strong scent.
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other countries, but must be listed on the label if present above allergen thresholds (e.g., EU CosIng).
- Common uses
- Fragranced skincare, Perfumes, Body lotions, Cleansers
- Environmental note
- As a synthetic compound, it is not biodegradable and may accumulate in the environment, though its low usage concentration limits impact.
Good to know
- Fragrance ingredients like this one are often listed simply as 'parfum' or 'fragrance' on labels, so you may not see the specific name.
- Regulations in many regions require fragrance allergens to be listed separately if they exceed certain thresholds.
Common questions
What is Trans-Trimethylundecadienal in beauty products?
This is a man-made chemical that smells like fresh flowers or citrus. It is added to products to make them smell nice, but it does not moisturize, treat, or improve your skin in any way. If you have sensitive skin or avoid fragrance, you may want to skip products containing this ingredient.
What does Trans-Trimethylundecadienal do in a beauty product?
In a cosmetic product, it simply evaporates from the skin's surface, releasing a pleasant floral or citrus-like aroma. It has no active role in cleansing, moisturizing, or protecting the skin.
Is Trans-Trimethylundecadienal safe for most people?
Generally considered safe for most people at the low concentrations used in cosmetics. However, it can cause allergic reactions in fragrance-sensitive individuals, and its use is regulated as a potential allergen in several regions.
Who should be careful with Trans-Trimethylundecadienal?
Individuals with sensitive, reactive, or eczema-prone skin Anyone who prefers 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.