What is Diethyl phthalate?
Diethyl phthalate (DEP) is one of a number of phthalates (pronounced thalates), all of which have different uses and safety profiles. It is a colourless liquid that is used as a solvent in nail polish remover, detergent and cleaning agents and as a fixative in fragrances. It may also be used as an ‘alcohol denaturant’ – that is, an additive to products containing alcohol that gives it a foul smell, making it unfit to drink. Many phthalates have been banned from use in plastics and cosmetics as they are considered to be a hazard to reproductive health. DEP however is still considered safe when used at appropriate levels for use in cosmetics although many products are phasing it out due to concerns about its possible role as an endocrine disruptor. It is not considered to be toxic or carcinogenic but it may irritate the skin and eyes.
What does it do?
Diethyl phthalate is currently used through direct addition in cosmetic products and personal care products and indirectly in fragrances. Diethyl phthalate is used as solvent and vehicle for fragrance and cosmetic ingredients, as well as an alcohol denaturant – that is, an additive to alcohol to make it unfit to drink.
In cosmetics it is used in the preparations of oils, eye-shadows, perfumes, hair sprays, nail polish, bath soaps, after-shave lotions, and skin care preparations.
DEP is the only phthalate still periodically used in cosmetics, and its use is very limited; in fact, many personal care product manufacturers are discontinuing its use as an ingredient.
While other phthalates have been banned in the EU Diethyl Phthalate (DEP) is still in use and considered safe if used at appropriate levels. While it is suspected of interfering with hormone function (endocrine disruption), causing reproductive and developmental problems it is not considered to be carcinogenic.
DEP has a low order of acute oral toxicity and may irritate the skin and eyes. It is not stored in the body.
The Environmental Working Group gives it a rating of ‘3’ or ‘fair’ (overall low level) on it’s risk assessment level.
Dimethyl benzene-1, 2-dicarboxylate
 Api, A.M. (2001). “Toxicological profile of diethyl phthalate: a vehicle for fragrance and cosmetic ingredients”. Food and Chemical Toxicology. 39 (2): 97–108
 ATSDR (1995) Toxicological profile for diethyl phthalate. Agency for Toxic Substances and Disease Registry, Division of Toxicology/Toxicology Information Branch, 1600 Clifton Road NE, E-29, Atlanta, GA 30333.