Key takeaways
- Typical dose is 0.3–1% in leave-on, higher in rinse-off.
- EU rules require disclosure of 26+ declarable allergens above 0.001%/0.01%.
- Fragrance can discolour, thicken or destabilise a formula.
Fragrance is the ingredient most often responsible for cosmetic contact allergy, and it is also the ingredient most often added last, at a dose chosen by smell rather than by specification. The dose, the allergen content and the stability behaviour all need to be decided before the formula is finalised.
1. Dose
Leave-on products typically use 0.3 to 1 percent fragrance; rinse-off products can go higher because contact is short. Above 1 percent in a leave-on product the irritation risk rises and the allergen declaration grows. A body lotion at 0.5 percent is a normal, defensible dose.
2. Allergen disclosure
In the EU, any of the declarable fragrance allergens above 0.001 percent in a leave-on product or 0.01 percent in a rinse-off must be listed on the label. A fragrance with a high allergen content produces a long INCI line and a longer label. Ask the supplier for the allergen declaration before choosing the scent.
3. Stability
Fragrance components oxidise, and oxidised fragrance is more allergenic than fresh fragrance. Limonene and linalool oxidise readily; antioxidants and an opaque pack slow it. A product that smells slightly different at month twelve is a product whose fragrance has changed chemically.
4. Discolouration
Vanilla, citrus and some floral notes discolour a white emulsion to cream or pink within months. The discolouration is usually cosmetic rather than toxic, but it generates complaints. Choosing a fragrance with a stability statement, or accepting a tinted base, avoids the issue.
5. Interaction with the formula
Fragrance can thicken an emulsion, break a gel or reduce preservative efficacy. Adding 1 percent of a solvent-based fragrance to a carbomer gel can collapse the viscosity. Test the fragrance in the finished formula, not in a blank base.
6. Masking versus scenting
Many products use fragrance to mask a base odour rather than to create a scent. Masking needs a low dose and a neutral note; scenting needs a higher dose and a defined accord. Confusing the two produces a product that smells like neither.
7. Fragrance-free versus unscented
“Unscented” can mean no fragrance added but a masking agent present; “fragrance-free” means no fragrance material at all. These are different claims and some markets regulate them. Choose the wording that matches the formula.
8. Natural essential oils
Essential oils are fragrance by another name and carry a higher allergen load per dose than most synthetic accords. A lavender oil at 0.5 percent can push several allergens over the disclosure threshold. The “natural” positioning usually increases the allergen list, not decreases it.
9. Testing
A fragrance change requires a re-run of the stability protocol and, if the dose rises, the challenge test. Human repeat insult patch testing on 50 subjects is the standard for a leave-on product with a new fragrance, and it costs less than a reformulation after a complaint.
10. Cost
Fragrance concentrates cost from tens to hundreds of dollars per kilo. At 0.5 percent in a 200 ml lotion the cost is small; at 2 percent in a fine fragrance it dominates the formula. The dose should be the lowest that delivers the intended scent.
11. Where it fits
Fragrance decisions run across the body lotion range; the preservation interaction continues in the preservation entry.
Reference: Fragrance supplier documentation and allergen labelling review, 2025
