The reason we chose PEGs to complement PG, is that PEGs have amazing properties: they are non-toxic, inert (non-reactive with other chemicals), odorless, colorless, soluble in many organic solvents, nonirritating and do not evaporate easily.
These characteristics of PEGs make them excellent materials for use in the pharmaceutical industry. PEGs are used as lubricants and are employed in a variety of pharmaceutical products as solvents, dispensing agents, ointments, delivery liquids for medications, fillers for tablets, as suppository bases, in ophthalmic solutions and as a treatment for constipation. PEGs are also used in veterinary products.
In the process of our research in creating the EJmix, we referenced the medical text "Natural and Synthetic Biomedical Polymers" (Kumbar, Laurencin, Deng) that further lists the use of PEGs as burn ointment, hepatitis treatment, and as a potent agent in nerve repair. It is also the most effective known agent for the suppression of chemical carcinogens (cancer) in rats (although it has not been tested on humans):
When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood. This makes for a longer-acting medicinal effect and reduces toxicity, and allows longer dosing intervals. Examples include PEG-interferon alpha, which is used to treat hepatitis C, and PEGfilgrastim (Neulasta), which is used to treat neutropenia. It has been shown that polyethylene glycol can improve healing of spinal injuries in dogs. One of the earlier findings, that polyethylene glycol can aid in nerve repair, came from the University of Texas (Krause and Bittner). Polyethylene glycol is also commonly used to fuse B-cells with myeloma cells in monoclonal antibody production.
And if you don't think you're exposed to PEGs everyday, look again: if you take good care of your teeth, you probably are as PEGs are used in toothpastes, breath fresheners and mouthwashes, including anti-plaque and antiseptic mouth rinses. PEGs are used to keep all ingredients in solution and to increase the shelf-life and stability of the products.
So to summarize why PEGs?
Because they are non-toxic, have an extensive history of medical use, and do an excellent job of keeping all sorts of ingredients together in a stable solution.