LYRAL
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Note : Base
CAS Number : 31906-04-4
IUPAC Name : 4-(4-Hydroxy-4-methylpentyl)-1-cyclohex-3-enecarboxaldehyde
Other Names : HICC, Leerall, Cyclohexal, Kovanol, Mugonal, Landolal, Lysinal, Kovyral, Lydoucal, Lanyral
Molecular Weight : 210.31674
Vapor Pressure : 0.000029 [mm/Hg] @ 25.00 C
Density : 0.995 [g/cm]
Appearance : Colorless to pale yellow clear viscous liquid
Boiling Point: 318.65 C @ 760.00 [mm Hg]
logP: 2.080 (P: Partition coefficient)
Substantivity : 400 hours
Relative Odor Impact : 100 // References: Iso E Super (100); Hydroxycitronellal (100); Ethyl Maltol (250); Furaneol (743)
IFRA : Restricted (Sensitization) Cat. 3 (Hydroalcoholics for Shaved Skin): 0.2% - Cat. 4 (Hydroalcoholics for Unshaved Skin): 0.2%

To My Nose:
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Pure : Most larger odoriferous molecules (molecular weight > 200) cannot always be detected by smelling pure, directly from the bottle. In the case of Lyral, I can get it, but the aroma is tenuous and different from diluted versions. It overwhelms/saturates inmediately its primary olfactory receptors.

0.2% v/v solution in ethanol applied on blotter : I don't have much to add to what has already been said about how Lyral smells: "Soft delicate floral, lily, cyclamen, lilac note reminiscent of hydrocycitronellal. Extraordinary tenacity and diffusivity. A powerful blending agent giving richness throughout all dryout phases of a perfume composition" (IFF). "Sweet-floral, at first delicate and refreshingly mild, but often increasing in odor strength after short olfactory study. The floral notes are mild, light and resemble lily of the valley. The tenacity is good, and the odor diffusion increases significantly when the material is properly blended with lower boiling odorants or modifiers." (Steffen Arctander).

Notes:
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"Muguet" is the French word for lily of the valley.

Lyral "was" a trademark of IFF (expired - last cancellation date: September 21, 2012).

Lyral smells similar to hydroxycitronellal (not identically). However Lyral, at least, doubles its substantivity. I did the following test: I made three solutions: (a) Lyral @0.2%, (b) Hydroxycitronellal @1% and (c) [Lyral @0.2% + Hydroxycitronellal @1%].

Then I placed equal parts in three separate blotters. Fragance (b) opens slightly intense than (c) and stronger than (a).

Due to properties of Lyral (very low vapor pressure), mixture (c) is a bit weaker than (b), but more rounded, diffusive and rich.

24 hours later, aroma on hydroxycitronellal only blotter almost vanished. At the same time, I can smell a mild floral on [Lyral + Hydroxycitronellal] blotter. Surprisingly for me, solution (a) is the strongest. So, Lyral extends the floral note during more stages of the perfume's life. However, from my experience, if a muguet floral base note is needed, perhaps it's better to use Lyral alone. It should be noted that the Lyral concentration used is five times less than hydroxycitronellal's one.

Why did I choose 0.2% as testing concentration? Because it's the maximum concentration recommended by IFRA for hydroalcoholics over skin (shaved/unshaved). The European Union went further last year: "The European Commission has updated the regulation to prohibit the use of Lyral (and other two substances - atranol and chloroatranol)". The reason: Sensitization.

But what is Sensitization? (Perhaps the most hated -and feared- word by the fragance industry today).

Sensitization is a dermatological term. But first is needed to understand what is "dermatitis" and, more specifically, "contact dermatitis".

Dermatitis is a medical condition in which the skin becomes red, swollen, and sore, sometimes with small blisters, resulting from direct irritation of the skin by an external agent or an allergic reaction to it.

Contact dermatitis is defined as changes that occur in the skin or its appendages (hair, nails, mucous membranes) as a result of contact with an exogenous agent.

Sensitizers are allergens. An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.

Once an individual is sensitized to an allergen, future contacts with the allergen can trigger a reaction, commonly known as a memory response, in the original site of sensitization. So for example if a person has an allergic contact dermatitis on the eyelids, say from use of makeup, touching the contact allergen with the fingers can trigger an allergic reaction on the eyelids.

This is due to local skin memory T-cells (T lymphocytes), which remain in the original sensitization site. In a similar fashion, cytotoxic T lymphocytes patrol an area of skin and play an important role in controlling both the reactivation of viruses (such as the "cold sore" virus) and in limiting its replication when reactivated. Memory response, or "Retest Reactivity", usually takes 2 to 3 days after coming in contact with the allergen, and can persist for 2 to 4 weeks.

Several complete books have been written on the subject of sensitization of the skin to external agents. Instances have been reported of sensitization to a vast number of the objects with which man comes in contact. Any of these may produce a dermatitis in sensitive subjects. The treatment is simple: remove the offending agent. If what is responsible cannot be determined have the patient stop using anything that has been applied to the affected area for a while and resume the use cautiously, one by one, after the dermatitis has disappeared.

There are different types of sensitization: Cross Sensitization (the patient is allergic to a substance and others which have some structural analogy with the first), Concomitant Sensitization (the patient is allergic to two or more substances not chemically related but present in the same product), Multiple Sensitizations (the person shows sensitization to several substances not chemically related or present in the same product).

Fragrance contact allergy constitutes a significant clinical problem. Frequency of contact allergy to perfumes is estimated to be 1%-2% in general population, and roughly 8% in contact eczema patients. This makes contact sensitization to fragrances among the most common cause of allergic contact dermatitis, next to nickel and preservative agents.

Lyral is considered one of the "Top 10 Scents" of the past 25 years, according to The European Union. Before restrictions it was found in over 35% of all beauty products.

Since 2003 attempts have been made by the fragrance industry to contain the outbreak of Lyral allergy, but with no convincing success so far. Then Lyral was banned.

For years Lyral has been used without restrictions in cosmetic products, until recently. According to a study published in Contact Dermatitis, in 16 of 18 cases (89%) of people with pre-existing eczema, an allergic reaction resulted from application of Lyral. Of the 18 patients, 11 reacted to the low and 5 to the high concentration. Lyral is identified as the cause of contact allergic reactions in 2-3% of eczema patients undergoing patch testing.

From Givaudan: Lyral, which also goes under the trade name Cyclohexal, has a lily-of-the-valley character, useful for perfumers, but which potentially provoked dermatitis-like allergies. Being aware of the threat allowed us to work on a replacement molecule, Mahonial. We researched this new synthetic for three years and it was successfully phased in as Lyral was being phased out. It enabled fine fragrance and consumer products perfumers to seamlessly continue their floral, lily-of-the-valley creations.

More Info:
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https://en.wikipedia.org/wiki/Hydrox...carboxaldehyde
http://www.thegoodscentscompany.com/data/rw1007972.html
https://www.perfumersworld.com/product/lyral-3MG00282
https://www.iff.com/smell/online-compendium/lyral
https://www.ncbi.nlm.nih.gov/pmc/art...00193-0066.pdf
https://www.acdlabs.com/download/app...king_sense.pdf
https://www.sgs.com/en/news/2017/08/...ance-allergens
https://ec.europa.eu/health/scientif...sccs_o_074.pdf
https://www.researchgate.net/publica...tacto_a_LyralR
https://en.wikipedia.org/wiki/Allerg...act_dermatitis
https://www.givaudan.com/sustainabil...er-regulations