Synthetic fragrance ingredient with a strong floral scent. (Also goes by the name 2-(4-tert-Butylbenzyl) propionaldehyde or lilial.) Butylphenyl methylpropional’s use in cosmetics is restricted due to concerns over sensitivity.
The presence of butylphenyl methylpropional 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, like cleansers and shampoos.
References for this information:
Global Regulatory Issues for the Cosmetics Industry, 2009, volume 2, pages 55-78