Peace be upon you. According to Grand Ayatollah Khamenei and Grand Ayatollah Sistani, there are no forbidden or impure substances in the composition of polyethylene glycol. Therefore, it can be considered pure and permissible to consume. There is no need to investigate its composition in cases of doubt. It is also used for medical treatment; even if it were not originally pure or permissible, it can be consumed out of necessity if treatment depends on it, and it should be used only as much as the medical necessity requires. May you be successful in all good.