Fragrance Blending & IFRA Limits
Creating Custom Scent Blends While Staying Within Safe Usage Limits
Creating custom fragrance blends allows you to design unique scents for your products. However, fragrances contain allergens and sensitizers that must be used within safe limits. The IFRA Calculator helps you determine the maximum safe usage rate for your 100% fragrance blend based on the IFRA limits of each component.
This guide will teach you the art of fragrance blending, how IFRA limits work, and how to use the calculator to create safe, compliant, beautifully scented products.
Understanding IFRA Limits
What is IFRA?
The International Fragrance Association (IFRA) sets safety standards for fragrance use based on scientific research into allergens and sensitizers. These standards protect consumers from adverse skin reactions.
Every fragrance oil should come with an IFRA certificate listing maximum safe usage rates for different product categories.
How IFRA Limits Are Calculated:
- Identify allergens: Each fragrance component is analyzed for known allergens (like linalool, limonene, citral, geraniol)
- Test concentrations: Scientific studies determine safe exposure levels for each allergen
- Calculate by category: Products are grouped by exposure type (leave-on vs rinse-off, skin contact vs inhalation)
- Set maximum limits: The highest allergen concentration determines the maximum safe usage rate for that fragrance
IFRA Categories (Common ones for makers):
| Category | Product Type | Typical Limit |
|---|---|---|
| Category 4 | Body lotions, face creams (leave-on) | Lower limits (e.g., 0.5-3%) |
| Category 9 | Soap, body wash, bath bombs (rinse-off) | Higher limits (e.g., 2-10%) |
| Category 12 | Non-skin contact (candles, wax melts, air fresheners) | Highest limits or unrestricted |
How the IFRA Calculator Works:
- You enter each fragrance component and its percentage in your blend
- The calculator looks up IFRA limits for each component (Category 9 for soap)
- It calculates the maximum safe percentage for your entire blend
- It shows allergen declarations required for EU labeling
- You get instant feedback on whether your blend is compliant
Fragrance Blending Basics
Understanding Fragrance Notes:
Top Notes (10-25% of blend):
First impression, evaporate quickly (5-15 minutes)
- Citrus: Lemon, Orange, Bergamot, Grapefruit
- Herbs: Basil, Mint, Eucalyptus
- Light florals: Lavender (also middle note)
Middle Notes (40-60% of blend):
Heart of fragrance, emerge as top notes fade (15-60 minutes)
- Florals: Rose, Jasmine, Ylang Ylang, Geranium
- Spices: Cinnamon, Clove, Nutmeg
- Green: Tea Tree, Pine, Rosemary
Base Notes (20-35% of blend):
Foundation, longest lasting (several hours), anchor lighter notes
- Woods: Cedarwood, Sandalwood, Patchouli
- Resins: Frankincense, Myrrh, Benzoin
- Musks: Vanilla, Amber, Vetiver
Classic Blend Ratio:
- 20% Top notes (bright, fresh)
- 50% Middle notes (character, body)
- 30% Base notes (depth, longevity)
Creating Blends with the IFRA Calculator
Step 1: Plan Your Blend
Before using the calculator, decide on your scent profile:
- Choose a theme (fresh, floral, earthy, spicy, etc.)
- Select 3-6 fragrances that complement each other
- Ensure you have IFRA certificates for each component
Step 2: Enter Components in Calculator
- Navigate to the IFRA Calculator
- Add each fragrance component
- Enter the percentage of each in your blend (should total 100%)
- Input the IFRA Category 9 limit from each certificate
Step 3: Review Results
The calculator shows:
- Maximum safe usage % of your 100% blend in your final product
- Which component is the limiting factor
- EU allergen declarations needed (if applicable)
Example Calculation:
Your blend contains:
- 40% Lavender (IFRA limit: 10%)
- 30% Patchouli (IFRA limit: 15%)
- 30% Bergamot (IFRA limit: 5%)
Calculator determines: Bergamot is the limiting factor. Your blend can be used at maximum 16.7% of your soap recipe (because 30% of 16.7% = 5%, which is Bergamot's limit).
Fragrance Blending Techniques
Testing Small Batches:
- Use test strips or cotton balls for initial trials
- Mix components in small amounts (1-5ml total)
- Let rest 24 hours - scents evolve and blend over time
- Adjust ratios based on how scent develops
- Test in actual product (small batch) before scaling up
Balancing Your Blend:
If blend is too sharp/bright:
Add more base notes (woods, musks) to round it out
If blend is too heavy/dull:
Add citrus or herbal top notes for brightness
If blend is too simple:
Add a middle note to create complexity
Pro Blending Tips:
- Start with 3 components, add complexity gradually
- One dominant note, others support (avoid equal percentages)
- Citrus and floral pair well; woods and spice pair well
- Always include a base note for staying power
- Less is more - start with low percentages
Popular Fragrance Blend Profiles
Spa Fresh:
- 30% Eucalyptus (top)
- 40% Lavender (middle)
- 30% Cedarwood (base)
Citrus Grove:
- 25% Sweet Orange (top)
- 45% Litsea Cubeba (middle)
- 30% Patchouli (base)
Garden Bouquet:
- 20% Bergamot (top)
- 50% Rose Geranium (middle)
- 30% Sandalwood (base)
Earthy Zen:
- 20% Bergamot (top)
- 40% Frankincense (base)
- 40% Vetiver (base)
Remember: Always check these blends in the IFRA calculator with your specific fragrance certificates before use!
Storing and Using Fragrance Blends
Storage:
- Dark glass bottles (amber or cobalt blue)
- Cool, dark location
- Airtight seals (oxidation degrades fragrances)
- Label with blend name, date, and ratio
- Use within 1-2 years for best performance
Usage Rates by Product:
| Product | Typical Range | Notes |
|---|---|---|
| Cold Process Soap | 3-6% of oils | Check IFRA Category 9; some fade with high pH |
| Body Lotion | 0.5-2% | Check IFRA Category 4; lower limits for leave-on |
| Body Wash | 1-3% | Category 9; rinse-off allows higher usage |
| Bath Bombs | 1-3% | Category 9; rinse-off product |
Important reminders:
- Always use the calculator to verify your final usage rate is safe
- Different product categories have different limits - recalculate for each use
- Label products with allergen declarations as required by law