6.2
ISS Score
B — Acceptable — low-moderate concern
↑ Higher = Safer
Environmental
(ESS)
(ESS)
—
Confidence
(CSS)
(CSS)
—
fragrance · masking agent · odor neutralizer
Acetyl Hexamethyl Tetralin
Molecular Formula
C18H26O
Molecular Weight
258.4 g/mol
Category
fragrance ingredient
Bottom Line: Acetyl Hexamethyl Tetralin (AHTN, tonalide) is a synthetic polycyclic musk used in fragrance. In the EU it is a restricted cosmetic ingredient (Annex III, entry 182: 2.5% in fine fragrance, 0.1% in other leave-on products). The EU scientific committee (SCCNFP, 2002) judged it safe up to 12% in the fragrance compound, but a proposal to classify it as toxic to reproduction (Repr. 1B) is under ECHA review, and it carries notified classifications as harmful if swallowed and very toxic to aquatic life. Its score reflects restricted status and limited verified toxicology data.
Quick Answer
✔ Generally Safe If:
- the finished product stays within the EU Annex III limits (for example 2.5% in fine fragrance)
- it is not applied to broken skin
- it is part of a well-formulated product
⚠ Use with Awareness If:
- you are pregnant, breastfeeding or trying to conceive (a reproductive-toxicity classification proposal is under EU review)
- you have sensitive skin
- you use several fragrance products on the same day
✕ Avoid If:
- you have known allergies to fragrance ingredients
- you experience irritation after use
- the product is a leave-on product above the EU limit for its category
Chemical Properties
| Property | Value |
|---|---|
| Molecular Formula | C18H26O |
| Molecular Weight | 258.4 g/mol |
| Melting Point | 54.5°C |
| Boiling Point | 326.0°C |
| Solubility | In water, 1.25 mg/L, temp not specified |
| Log P | 5.3 |
Common Use Cases
2 Categories
Cosmetic
Fine fragrance, personal-care products. Keep within the EU Annex III limits for the product category. Typical: EU limits: fine fragrance 2.5%, hydroalcoholic products 1%, fragrance cream 0.5%, other leave-on products 0.1%, rinse-off products 0.2%.
Household
Air fresheners, laundry products. Other sources of exposure (such as laundry products) add to cosmetic exposure (SCCNFP, 2002).
Safety by Route of Exposure
dermal
dermal
Risk Level: Low
Dermal exposure to Acetyl Hexamethyl Tetralin is generally considered low risk for skin contact.
oral
oral
Risk Level: Moderate
Ingestion of Acetyl Hexamethyl Tetralin may pose moderate risks, particularly in large amounts.
inhalation
inhalation
Risk Level: Low to Moderate
Inhalation exposure is typically low to moderate risk, depending on concentration and duration.
ocular
ocular
Risk Level: Moderate
Eye contact with Acetyl Hexamethyl Tetralin may cause moderate irritation.
Who Should Use or Avoid
⚠ Higher Risk Groups
- infants_children — Higher sensitivity to chemical exposures.
- pregnant — EU reproductive-toxicity classification proposal under review.
✔ Well-Tolerated Groups
- general_adult — Generally well tolerated in healthy adults.
- elderly — Typically well tolerated, but monitor for reactions.
Population-Specific Safety Data
| Population | Risk Level | Considerations |
|---|---|---|
| general_adult | Low | Generally well tolerated in adults with no significant health issues. |
| pregnant | Moderate | A proposal to classify tonalide as toxic to reproduction (Repr. 1B) is under ECHA review; the outcome is pending. |
| infants_children | High | Children may be more sensitive to chemical exposures. |
| breastfeeding | Low to Moderate | Limited data on transfer through breast milk; use with caution. |
| elderly | Low | Typically well tolerated, but individual sensitivities may vary. |
| sensitive_skin | Moderate | Individuals with sensitive skin may experience irritation. |
Toxicology Data
6 Endpoints
Tonalide (AHTN) is restricted in EU cosmetics. A 2002 EU scientific opinion supports use up to 12% in the fragrance compound, while a reproductive-toxicity classification proposal and an endocrine-disruption evaluation are under way.
| Endpoint | Value | Test Method | Interpretation | Source |
|---|---|---|---|---|
| Dermal absorption (in vitro) | 0.28% (24 h, unoccluded); 3.00% (occluded) | In vitro rat skin, ethanol / diethyl phthalate vehicle | Poorly absorbed; accumulates in skin layers | SCCNFP/0609/02 (2002) |
| Acute oral toxicity (classification) | Acute Tox. 4 (H302) | Notified CLP classification (ECHA C&L Inventory) | Harmful if swallowed | ECHA brief profile |
| Aquatic toxicity (classification) | Aquatic Acute 1 (H400); Aquatic Chronic 1 (H410) | Notified CLP classification (ECHA C&L Inventory) | Very toxic to aquatic life with long-lasting effects | ECHA brief profile; OECD SIDS (2009) |
| Reproductive toxicity | Repr. 1B proposed, not adopted | ECHA harmonised classification proposal (consultation closed 30 May 2025) | Under regulatory review | IFRA notice (2025) |
| Endocrine activity | Potential endocrine disruptor (under evaluation) | EU Rolling Action Plan, Germany | Under evaluation | Swiss Ecotox Centre (2020), citing EC 2020 |
| Skin sensitisation | Not established | No verified endpoint data in the sources reviewed | Insufficient data | — |
Data Quality: All toxicology values are sourced from verified regulatory assessments (CIR, SCCS, ECHA REACH) following OECD test guidelines. Values are used to calculate the Ingredient Safety Score (ISS).
Scientific Evidence
Key Assessments
Tonalide (AHTN) is restricted in EU cosmetics. A 2002 EU scientific opinion supports use up to 12% in the fragrance compound, while a reproductive-toxicity classification proposal and an endocrine-disruption evaluation are under way.
- Restricted in EU cosmetics: 2.5% in fine fragrance, 0.1% in other leave-on products
- EU scientific committee (SCCNFP, 2002): safe up to 12% in the fragrance compound
- Proposed Repr. 1B classification under ECHA review (outcome pending)
- Harmful if swallowed; very toxic to aquatic life (notified classifications)
Switch to Detailed mode to view full scientific assessments and citation database.
SCCNFP (EU scientific committee)
Report: Opinion concerning 6-Acetyl-1,1,2,4,4,7-hexamethyltetraline (AHTN), SCCNFP/0609/02
Year: 2002
Conclusion: AHTN can be safely used as a fragrance ingredient in cosmetic products up to a maximum concentration of 12% in the fragrance compound. Other sources of consumer exposure, such as laundry products, must be considered for a full assessment.
View Full Report →
EU Cosmetics Regulation 1223/2009
Report: Annex III, entry 182 (AHTN)
Conclusion: Restricted: fine fragrance 2.5%, hydroalcoholic products 1%, fragrance cream 0.5%, other leave-on products 0.1%, rinse-off products 0.2%.
View Full Report →
IFRA (fragrance industry association)
Report: Tonalide: proposed Repr. 1B classification (ECHA CLH)
Year: 2025
Conclusion: A harmonised classification proposal as toxic to reproduction (Repr. 1B) went to public consultation, which ended on 30 May 2025. Industry submitted comments opposing it. The ECHA Risk Assessment Committee discusses it next. Not an adopted classification.
View Full Report →
Swiss Centre for Applied Ecotoxicology
Report: Sediment quality criterion proposal for AHTN ("Tonalid")
Year: 2020
Conclusion: Summarising EU, OECD and Canadian work: registered under REACH; OECD SIDS (2009) found AHTN may present an environmental hazard (acute aquatic toxicity below 1 mg/L, not readily biodegradable); Germany scheduled it for EU Rolling Action Plan re-evaluation as a potential endocrine disruptor; Environment Canada found it not persistent and not bioaccumulative but inherently toxic to the environment.
View Full Report →
Regulatory Status
Global
Restricted in the EU under Annex III, entry 182 (for example 2.5% in fine fragrance and 0.1% in other leave-on products). A proposal to classify it as toxic to reproduction (Repr. 1B) is under ECHA review. Regulatory status in other jurisdictions has not been verified for this page. Switch to Detailed mode for full regulatory breakdown.
European Union
European CommissionRESTRICTED IN COSMETICS (ANNEX III, ENTRY 182)
Maximum concentration in the ready-for-use product: leave-on 0.1% (hydroalcoholic products 1%; fine fragrance 2.5%; fragrance cream 0.5%); rinse-off 0.2%. A harmonised classification as toxic to reproduction (Repr. 1B) has been proposed to ECHA; the public consultation closed on 30 May 2025 and the outcome is pending.
Frequently Asked Questions
It is a synthetic polycyclic musk, also called AHTN or tonalide, used to give fragrances a clean, musky note. It is used in fine fragrance, personal-care and household products.
Yes, in the EU. Annex III of the Cosmetics Regulation (entry 182) limits it to fine fragrance 2.5%, hydroalcoholic products 1%, fragrance cream 0.5%, other leave-on products 0.1%, rinse-off products 0.2%. The EU scientific committee SCCNFP judged it safe up to 12% in the fragrance compound (2002).
A harmonised classification as toxic to reproduction (Repr. 1B) has been proposed. ECHA's public consultation closed on 30 May 2025 and industry commented against it; the ECHA Risk Assessment Committee discusses it next. It is not an adopted classification. Germany has also flagged tonalide for EU re-evaluation as a potential endocrine disruptor.
Verified skin-sensitisation data were not available in the sources reviewed for this page. As with any fragrance material, patch testing is sensible if you have sensitive skin.
It carries notified classifications as very toxic to aquatic life with long-lasting effects, and an OECD review (2009) found it may present an environmental hazard. Environment Canada categorised it as not persistent and not bioaccumulative, but inherently toxic to the environment.
Version History
Audit Trail
| Version | Date | ISS Score | What Changed |
|---|---|---|---|
| 1.0.0 - Initial enrichment | 2026-04-13T03:57:01.978059Z | — | Initial data enrichment via 3-phase structured outputs |
| 1.1.0 - Regulatory and evidence correction | 2026-10-29T21:15:32.190728+00:00 | 62 | Replaced unsourced regulatory status and evidence with the EU Annex III restriction, the 2002 SCCNFP opinion and the pending ECHA classification proposal; score re-evaluated. |
⚠ Important Notice: This information is for educational purposes only and does not constitute medical, professional, or regulatory advice. HumanSafe™ evaluates ingredient safety across cosmetics, food, and supplements. Scores are exposure-route and context-specific. Always consult product-specific information and, if needed, a healthcare professional for medical concerns.