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Journal Article 
Results of feeding propylene glycol in the diet to dogs for two years 
Weil, CS; Woodside, MD; Smyth, HF; Carpenter, CP 
Food and Cosmetics Toxicology
ISSN: 0015-6264
EISSN: 1878-6049 
Groups of five male and five female beagle dogs were fed diets containing propylene glycol or dextrose, the latter as equicalorific controls, for 2 yr. Dosage levels used were 5·0 and 2·0 g propylene glycol/kg and 6·35 and 2·54 g dextrose/kg, and in addition a control group received neither compound. The criteria of effect included mortality, body-weight change, diet utilization and water consumption, micropathology, liver, kidney and spleen weights, and measurements of blood, urine and biochemical parameters.

None of the criteria measured were significantly altered at 2 g propylene glycol/kg. The higher dose levels of propylene glycol and dextrose were maintained by the inclusion of approximately 20 and 25%, respectively, in the diets of the dogs. As both compounds provide calories available for conversion to adipose tissue, both groups gained somewhat more weight than the controls during the first part of the study. Propylene glycol, in high concentrations, increases the rate of erythrocyte haemolysis. When it was given at the 5-g/kg level, haemoglobin and haematocrit values and the total erythrocyte count were slightly low, while the incidence of anisocytosis, poikilocytes and reticulocytes was increased, findings indicative of erythrocyte destruction with accelerated replacement from the bone marrow. Even at a propylene-glycol concentration of 20% of the diet, this effect was not sufficient to result in any changes that appeared to be irreversible and there was no evidence of damage to bone marrow or spleen. The majority of parameters relevant to effects on the liver were similar in all dosage groups. In dogs consuming 5 g propylene glycol/kg there was a slight increase in total bilirubin.

It is concluded that propylene glycol fed to dogs at a concentration of approximately 8% in the diet (2 g/kg/day) is utilized as a carbohydrate energy source without any adverse effects.