Every e-liquid on the market — whether a $30 craft juice or a $5 gas station disposable — starts with the same four ingredient categories. The proportions and quality vary, but the chemistry does not.
| Ingredient | Typical % by Volume | Primary Function | FDA Status (Ingestion) | Safety When Heated & Inhaled |
|---|---|---|---|---|
| Propylene Glycol (PG) | 20-50% | Flavor carrier, throat hit, viscosity thinner | Produces formaldehyde, acetaldehyde, methylglyoxal above 350°C | |
| Vegetable Glycerin (VG) | 50-80% | Vapor production, sweetness, smoothness | Produces acrolein, glycidol above ~280°C | |
| Nicotine | 0.3-5% (3-50 mg/mL) | Active ingredient, dependence potential | Tobacco product | Addictive; salt form delivers faster, higher blood concentrations |
| Flavoring compounds | 1-10% | Taste, aroma, product differentiation | Varies by compound | Some (diacetyl, cinnamaldehyde) show significant cytotoxicity |
