TABLE 1.

Properties of DEGEEs relevant to use as a solvent in topical formulations44,45,53–55,61,62

CATEGORY	COMMENTS
Official United States Pharmacopeia name/ category	•DEGEE •Glycol ether solvent used for transdermal, ocular, and intranasal delivery •Pharmaceutical grade DEGEE with 99.9% purity; abolishes the adverse events previously associated with industrial-grade DEGEEs •May be listed as ethoxydiglycol by the International Nomenclature of Cosmetic Ingredients
Physical properties	•Colorless liquid •Stable under ordinary conditions •Hygroscopic •Compatible with commonly used solvents, including oleic acid, propylene glycol, and ethanol •Spreads easily without streaking
Biologic properties	•Nonirritating •Nonallergenic •Not carcinogenic, mutagenic, or genotoxic •Enhanced solubility and intracutaneous penetration of various topical ingredients (e.g., clobetasol propionate, mometasone furoate) with increased skin retention (e.g., dexamethasone, hydrocortisone) •Increased reservoir capacity of the stratum corneum for several active ingredients (intracutaneous depot effect) with decreased systemic exposure (body burden) •Systemic absorption of DEGEE after topical application without systemic toxicity (5%”40% DEGEE concentration in available products) •Negligible antimicrobial effects •Compatible with skin surface lipids (i.e., epidermis/stratum corneum, sebum)

DEGEE: diethylene glycol momoethyl ether