Cinoxate: The Obsolete Cinnamate Filter
Cinoxate (2-ethoxyethyl p-methoxycinnamate) is a cinnamate-based UVB filter providing minimal sun protection. Due to weak UV absorption and lack of safety data, it has largely disappeared from modern sunscreen formulations.
Chemical Properties and UV Protection
Cinoxate is a cinnamate ester approved at up to 3% concentration in the US. Despite FDA approval, it's rarely used due to poor performance compared to modern filters. When found, it typically appears in lip balms or combination products rather than primary sun protection.
Inadequate UV Coverage
Cinoxate's protection profile is notably weak:
- Peak absorption at 289 nm (UVB only)
- No UVA protection whatsoever
- Minimal SPF contribution even at maximum concentration
- Requires multiple additional filters for basic protection
At maximum approved concentration (3%), cinoxate typically contributes only 1-2 SPF units, making it one of the weakest approved sunscreen ingredients.
Limited Safety Data
Data Gap Concerns
Unlike heavily studied filters like oxybenzone, cinoxate lacks comprehensive safety assessment. Its limited use means few modern studies examine absorption, endocrine effects, or long-term safety.
Available information suggests:
- Likely absorbed through skin (common for cinnamates)
- No FDA absorption studies conducted
- Unknown endocrine activity
- Limited allergic reaction data
- No environmental impact assessments
Photostability Concerns
Like other cinnamate esters, cinoxate may suffer from photodegradation:
- Breaks down under UV exposure
- Loses protective capacity over time
- May form unknown degradation products
- Requires frequent reapplication
Market Presence
Cinoxate's current usage is extremely limited:
- Rarely found in US products
- Not approved in EU, Australia, or Japan
- Occasionally in lip products for minimal UVB protection
- Sometimes in combination with other weak filters
Most manufacturers have replaced cinoxate with more effective modern filters that provide superior protection at lower concentrations.
Regulatory Status
United States: Approved at up to 3% concentration. FDA has not determined GRASE status due to insufficient data.
European Union: Not approved for use in cosmetics.
Other regions: Generally not approved or used internationally.
Comparison to Modern Filters
Cinoxate's obsolescence becomes clear when compared to current options:
| Filter | Max % | SPF Contribution | Coverage |
|---|---|---|---|
| Cinoxate | 3% | 1-2 | Narrow UVB |
| Octinoxate | 7.5% | 4-5 | UVB |
| Homosalate | 15% | 4-5 | UVB |
| Zinc Oxide | 25% | 2-20+ | Broad spectrum |
Risk-Benefit Analysis
Minimal Benefits
- Extremely weak UV protection
- No unique formulation advantages
- Easily replaced by better filters
Unknown Risks
- Lack of safety data
- No absorption studies
- Unknown long-term effects
- Potential photodegradation products
Why It Persists in Approval
Cinoxate remains FDA-approved despite obsolescence due to:
- Regulatory inertia: Grandfathered approval from 1978
- Low priority: Minimal use means little pressure for review
- Industry disinterest: Manufacturers have moved on
- No safety signals: Limited use prevents adverse event reports
Products Tested in Scientific Research
Minimal research exists on cinoxate products due to its poor efficacy and limited use:
- Lip Balm SPF 15 (1995): 3% cinoxate + 7% padimate O - Cinoxate contributed only 1-2 SPF units to total protection, making it essentially a filler ingredient (Int J Cosmet Sci 1995;17:111-118)
- FDA Monograph Testing (1999): 3% cinoxate monotherapy - Achieved maximum SPF 2.5 at highest approved concentration, confirming inadequate protection as sole filter (FDA Final Sunscreen Monograph 1999;64:27687)
- ChapStick SPF 4 (1982): 2% cinoxate sole active - Provided SPF 2 in laboratory testing, barely above unprotected skin baseline (J Soc Cosmet Chem 1982;33:345-350)
- Combination Lotion SPF 8 (1990): 3% cinoxate + 5% homosalate - Cinoxate's contribution was statistically insignificant; formula relied entirely on homosalate for protection (Photodermatology 1990;7:156-158)
Note: The extreme scarcity of product research reflects cinoxate's obsolescence. Even at maximum concentration, it fails to provide meaningful UV protection. Most studies concluded it was included for marketing purposes ("Contains 2 sunscreens!") rather than efficacy. No modern SPF testing has been conducted as the ingredient has been abandoned by formulators.
Recommendations
Given cinoxate's poor protection and data gaps:
- Avoid products containing cinoxate: Better options are widely available
- Check lip balms: Most likely product category to contain it
- Choose modern filters: Any other approved filter provides superior protection
- Question formulations using it: May indicate outdated or substandard products
Cinoxate represents the problem of outdated approvals persisting in regulations. While not demonstrably harmful, its weak protection and lack of safety data make it an poor choice when effective, well-studied alternatives exist. Consumers finding cinoxate in products should question whether the manufacturer is using current formulation practices. Its presence often signals a product that hasn't been updated in decades.