Gisou Honey Infused Hair Perfume Versus Olaplex No.7 Bonding Oil

You should know this ingredient is a known EU fragrance allergen.

Animal studies classifies this ingredient as a weak-to-moderate skin sensitizer and clinical patch testing on eczema patients confirmed it to be both a contact allergen and irritant.

The term 'citral' is a collective term for two geometric isomers: geranial/Citral A and neral/Citral B.

The term 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term. For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance.

Typical use levels are very low since the total fragrance load in a product is usually well under 1% and citronellol is only a small fraction of that.

The EU asks brands to name it on the label once it goes above 0.001% in leave-on products of 0.01% in rinse-off ones.

It is one of the EU's labeled fragrance allergens but real-world patch testing has shown it to be fairly weak and an infrequent allergen; positive reactions land around 0.1-0.9% of patients across recent European dermatitis clinic studies.

The bigger nuance is oxidation. Citronellol forms hydroperoxides when it reacts with air. These hydroperoxides are more sensitizing than the fresh ingredient, and patch test studies confirmed oxidized Citronellol causes more reactions than purified.

This means good packaging and freshness matter more than the molecule itself.

Fragrance can be irritating to very reactive or compromised skin, so people with sensitive skin may still prefer to skip it.

You'll typically see this ingredient used in very small amounts; anything above 0.001% in a leave-on product or 0.01% in a rinse-off has to be named on the label in the EU. The citrus oils that carry it sit around 0.5-1% in a finished formula.

Fresh limonene is a weak allergen; the real issue is that it slowly reacts with air and then breaks down from oxidation to create hydroperoxides (which are strong sensitizers). This is why suppliers are required to keep the peroxide value below 20 mmol.

Positive reactions in people being investigated for eczema vary:

It's worth skipping if you have a known fragrance allergy or a compromised barrier, but the risk is low for most people.

Older or long-opened products are also more likely to bother you than fresh ones due to oxidation.