Al-Rehab Choco Musk Perfume Oil

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.

The EU requires it to be named on the label above 0.001% in leave-on and 0.01% in rinse-off products.

Fresh linalool is a weak sensitizer but air exposure turns some of it into hydroperoxides, which are strong sensitizers. Those oxidation products are the actual allergy concern.

Patch-test clinics see positive reactions to linalool hydroperoxides in about 4% to 12% of dermatitis patients depending on country and test concentration.

Resassuringly, one analytical study found hydroperoxide levels in real fragranced products to be orders of magnitude below what induced sensitization in animal studies with no evidence of oxidation building up during normal storage.

The practical takeaway is that linalool is fine for most people but worth avoiding if you have a confirmed fragrance contact allergy or a badly compromised barrier.

Products stored a long time after opening are also the high-risk scenario since that is when oxidation happens.

The scent of linalool is described as floral, spicy tropical, and citrus-like.

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.

Citronellol is a modified terpene. Terpenes are unsaturated hydrocarbons found in plants. They make up the primary part of essential oils.

Citronellol is not able to be absorbed into deeper layers of the skin. It has low permeability,

Citronellol is also a natural insect repellent.

Geraniol can be found in many essential oils including Rose Oil and Citronella Oil. The scent of Geraniol is often described as "rose-like". Many foods also contain Geraniol for fruit flavoring.

Geraniol can irritate the skin when exposed to air. However, irritation depends on the ability of geraniol to penetrate into the skin. In general, geraniol is not able to penetrate skin easily.

Geraniol is colorless and has low water-solubility. However, it is soluble in common organic solvents.

Like citronellol, it is a natural insect repellent.

2,6-Octadien-1-ol, 3,7-dimethyl-, (2E)-

In many countries, coumarin is banned as a food additive. However, it can be found in soaps, tobacco products, and some alcohol drinks.

Plants use coumarins as a chemical defense. Some plants that have coumarins include lavender, tonka beans, and yellow clovers.

There's some lab work behind its reputation; in one study, it acted as an antioxidant and calmed inflammation in human immune cells. But it also killed skin cells (keratinocytes) in a dish.

It stopped damaging those cells and still reduced swelling in mice when the researchers wrapped it in tiny capsules to slow its release.

One study that is quoted out of context frequently: clove oil killed human skin and blood vessel cells at levels as low as 0.03%, and about 73% of that came down to eugenol. Keep in mind those were bare cells sitting in a dish with no skin barrier in the way (which is a lot harsher than what happens on your actual face).

On concentrations, it is restricted to 0.64% in leave-on products + body products, 0.21% in baby + lip products, 2.5% in fine fragrance and 4.9% in rinse-off. Real formulas usually land far below those caps.

Allergy is the actual story with this ingredient. It is one of the eight markers dermatologists use for allergy testing, and the EU requires it to be named on the label above 0.001% in leave-on and 0.01% in rinse-off products.

It is also a prohapten, meaning it needs enzymatic activation in skin to become allergenic, so sensitivity varies between people.

Rates are modest but not trivial: in a classic EECDRG multicentre study, 13 of about 1,300 patch-tested patients reacted to eugenol, and in eugenol-allergic subjects the lowest positive patch test concentration was 0.031%, with 56% reacting in a 21-day repeated open application test at 0.5% to 2.7%.

Normal use levels are generally fine if you are not already sensitized.

This ingredient is hydrophobic, meaning it is not soluble in water.

Solvents are used to keep ingredients together in a product. They can help dissolve ingredients to stable bases or help evenly distribute ingredients throughout the product.

Due to its fragrance, Benzyl Benzoate can be sensitizing and may cause contact dermatitis. It is a known EU allergen. We recommend speaking with a professional if you have any concerns.

Benzyl Benzoate can be naturally found in cranberries and peaches.

While Benzyl Salicylate has been associated with contact dermatitis and allergies, emerging studies show it may not be caused by this ingredient alone.

However, this ingredient is often used with fragrances and other components that may cause allergies. It is still listed as a known allergen in the EU. We recommend speaking with a professional if you have concerns.

Another study from 2021 shows Benzyl Salicylate may have anti-inflammatory properties.

Because it's one of the most well documented fragrance sensitizers, it's one of the substances that must be individually declared on EU ingredient lists once it exceeds 0.001% in leave on products or 0.01% in rinse off products (regardless of whether it's added on its own or shows up as part of a natural extract).

Industry usage limits are also fairly tight and the recommended maximum dropped from 0.2% to 0.02% in most finished cosmetic products.

On the skin side, Isoeugenol is consistently one of the top individual allergens within the standard patch test screen used by dermatologists.

A large multi-year patch test review found the rate of positive reactions to Isoeugenol was actually trending upward over time and controlled use tests found some sensitized people reacted to concentrations well below 0.01%. Roughly two thirds of people in this review also reacted at the industry recommended max of 0.2%.

It's not a "dangerous" ingredient at regulated concentrations, but is is a well-characterized contact allergen.

Naturally occurring Alpha-Isomethyl Ionone may be found in Saccharomyces cerevisiae, or the yeast used to make wine and bread.

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.

Hexyl Cinnamal is not water soluble but is soluble in oils.