Undecylenic Acid — Allergy Risk & Safety Profile
INCI: UNDECYLENIC ACID
Key Facts
- CAS Number
- 112-38-9
- Category
- preservative
- Risk Level
- low
- Common Allergen
- No
- Found In
- foot care, deodorant
Is Undecylenic Acid safe in cosmetics?
Undecylenic Acid is rated low risk in cosmetic products. It is not classified as a common allergen and is generally well-tolerated by most skin types. Safer alternatives include Phenoxyethanol, Sodium Benzoate, Potassium Sorbate. Commonly found in foot care, deodorant.
What is Undecylenic Acid?
Undecylenic Acid is a preservative commonly used in cosmetic and personal care products. It is generally considered safe for use in cosmetics at recommended concentrations.
Allergy & Safety Information
Undecylenic Acid is considered safe for cosmetic use at typical concentrations.
This ingredient is considered low risk from an allergenicity perspective. Reactions are uncommon at typical cosmetic use concentrations. However, no ingredient is universally safe — if you notice redness, itching, or irritation after using a product containing this ingredient, discontinue use and monitor whether symptoms resolve.
About Preservative Ingredients
Preservatives prevent microbial growth in water-containing cosmetic formulas. Without them, products would spoil within days. However, preservatives are among the most common causes of allergic contact dermatitis — they must be present in high enough concentrations to be effective, yet that same efficacy can irritate sensitised skin.
Relevance for Undecylenic Acid: If you react to one preservative, you may be cross-reactive to others in the same chemical family (e.g., isothiazolinones, formaldehyde releasers, or parabens). Checking the full preservative profile of every product you use is the most reliable way to identify your personal trigger.
How to Identify Undecylenic Acid in Products
Cosmetic ingredients are listed by their INCI (International Nomenclature of Cosmetic Ingredients) name in descending order of concentration. To check whether a product contains Undecylenic Acid, scan the ingredient list for its INCI name exactly as it appears above. Ingredients present at 1% or less may appear in any order after the 1% threshold.
Product types to prioritise checking: Foot care, Deodorant. These product categories are the most common sources of Undecylenic Acid exposure based on formulation data.
Not sure if your products contain Undecylenic Acid? Paste the ingredient list into the free ingredient checker to scan for Undecylenic Acid and other allergens automatically.
Safer Alternatives
These ingredients serve a similar function with lower allergy risk:
Frequently Asked Questions
Is Undecylenic Acid safe for sensitive skin?
Undecylenic Acid is generally well-tolerated, even by sensitive skin.
What products contain Undecylenic Acid?
Undecylenic Acid is commonly found in foot care, deodorant.
What does Undecylenic Acid do in cosmetics?
Undecylenic Acid functions as a preservative in formulations.
Related Guides
Preservative Allergy Guide
Which preservatives cause the most reactions and what to use instead.
How to Read Ingredient Labels
Decode INCI names and find hidden allergens in your products.
Find Your Skin Allergy Trigger
Step-by-step elimination method to identify your trigger.
Contact Dermatitis Guide
Symptoms, causes, patch testing, and treatment options.
Is Undecylenic Acid causing YOUR skin reactions?
SkinDetekt tracks your products and reactions to find your personal triggers. Download the app to find out.
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