Butylphenyl methylpropional is a synthetic fragrance ingredient that is used in a variety of cosmetics and personal care products due to its potent floral scent.
Butylphenyl methylpropional, also known Lilial or lily aldehyde, is a synthetic aromatic aldehyde. It is a commonly produced as a racemic mixture, which means it has equal amounts of left- and right-handed enantiomers. However, testing has found that the different enantiomers of the compound do not contribute equally to its odor. The (R)-enantiomer has a strong floral odor, similar to cyclamen or lily of the valley, whereas the (S)-enantiomer possesses no strong odor.
Butylphenyl methylpropional exists as a colorless to pale yellow liquid. In addition to use in cosmetics, butylphenyl methylpropional may be used in non-cosmetic products such as household cleaners and laundry detergents.
In cosmetics and personal care products, butylphenyl methylpropional functions as a fragrance ingredient due to its strong floral scent. It is used in aftershave lotions, bath products, bubble baths, cleansing products, hair care products, moisturizers, perfumes and colognes, shampoos and skin care products.
Butylphenyl methylpropional is an aldehyde, which is a family of ingredients that can either be natural or synthetic. Rose, citronella, cinnamon bark, and orange rind all contain natural aldehydes. Synthetic aldehydes are created by the partial oxidation of primary alcohols. All aldehydes contain a carbonyl (C=O) functional group. The carbon atom of this functional group has two remaining bonds that may be occupied by hydrogen or any generic alkyl or side chain. If at least one of these substituents is hydrogen, the compound is an aldehyde.
An article by Perfume Shrine explains that aldehydes vary in smell. For instance, most of the lower molecular weight aldehydes have an unpleasant odor, like rotten fruits. Some of the higher molecular weight aldehydes and aromatic aldehydes (like butylphenyl methylpropional) smell quite pleasant and are thus used in perfumery. Butylphenyl methylpropional has a molecular weight of approximately 204, which is high compared to formaldehyde, the simplest aldehyde, with a molecular weight of about 30.
Aldehydes can also boost the projection of a scent, or its sillage. Sometimes referred to as “lift,” sillage is how far a scent travels away from the wearer, not how long it lasts on the skin. An article by Elle explains, “It’s different from the intensity or power of a scent; sillage is more of an aura.” However, a bold sillage can have a room-filling effect, such as when someone enters an elevator and the perfume overwhelms the space. Thus, using an appropriate amount of aldehydes in a perfume is important to find the ideal sillage: not too strong, but not too weak.
One disadvantage of using butylphenyl methylpropional in products is that this ingredient tends to slowly oxidize on storage and is not stable long term. This problem occurs with most aldehydes.
The safety of butylphenyl methylpropional has been evaluated by the Research Institute for Fragrance Materials Expert Panel (REXPAN). Based on this evaluation, an International Fragrance Association (IFRA) Standard has been established. The IFRA Standard restricts the use of butylphenyl methylpropional in fragrances because of potential dermal sensitization.
A research article published in the Flavour and Fragrance Journal assessed the risk of sensitization for 26 fragrances in 5451 products from 2007 to 2009. As an estimate of sensitization risk, the sensitization exposure quotient (SEQ), was calculated as the quotient of the relative frequency of sensitization and the relative frequency of use/labelling. The SEQs (the risk) varied greatly, with butylphenyl methylpropional at the bottom of the list, indicating a very low risk of sensitization.
Since there is risk for sensitization with butylphenyl methylpropional, its presence must be indicated in the list of ingredients if the product contains more than 0.001% and is meant to be left on skin. It also must be listed if the product contains more than 0.01% and is meant to be rinsed, such as with cleansers and shampoos.
Due to the possibility of an allergic reaction, those with sensitive skin should try to butylphenyl methylpropional or perform a patch test with any product containing this ingredient.
References: Wikipedia, “Lillial”, Flavour Fragr. J., 2015, 30: 208–217, Cosmetics Info, “Butylphenyl methylpropional”, European Commission Scientific Committee on Consumer Safety “OPINION ON Butylphenyl methylpropional (BMHCA)”, 2016.