Use in Cosmetics. Dibutyl phthalate (pronounced thal-ate), or DBP, is used mainly in nail products as a solvent for dyes and as a plasticizer that prevents nail polishes from becoming brittle.Phthalates are also used as fragrance ingredients in many other cosmetics, but consumers won't find these listed on the label.elated Ingredients. Other phthalates are widely used as fragrance ingredients in cosmetics — in particular diethyl phthalate (DEP). DEP is suspected of interfering with hormone function (endocrine disruption), causing reproductive and developmental problems among other health effects.