What Are PG and VG in CBD Vapes? Why You Must Never Heat and Inhale Oral MCT Oil

[Published 2026-10]This article explains the roles of base ingredients (PG and VG) in CBD vape e-liquids and why putting oral CBD oil (such as MCT oil) into a vape device for inhalation is dangerous.

Because both "CBD oil" and "CBD e-liquid (for vaping)" are sold as liquids in bottles, they are easily confused,but their carrier bases are fundamentally different, and misusing them can lead to severe health hazards.

Table of Contents for this article.

Critical Differences Between Vape E-Liquids (PG/VG) and Oral Oils (MCT, etc.)
Why Inhaling Oral Oils (MCT Oil, Vitamin E Acetate, etc.) Is Dangerous
CBD, THC, and CBN Are Different Substances: Check the 2026 Regulations
4 Certificate of Analysis (COA) Checkpoints Before Purchase or Use
Why "Safe Because It Is CBD" or "Side-Effect-Free Because It Is Natural" Cannot Be Assumed

Critical Differences Between Vape E-Liquids (PG/VG) and Oral Oils (MCT, etc.)

Item	CBD E-Liquid for Vaping	Oral / Sublingual CBD Oil
Main Carrier Base (Base Ingredients)	PG (Propylene Glycol), VG (Vegetable Glycerin)	Edible oils and fats such as MCT oil (medium-chain triglyceride oil), olive oil, and hemp seed oil
Intended Use	Heated vaporization in compatible vape devices (*strictly avoid high-wattage overheating)	Oral ingestion (dropping under the tongue and swallowing, etc.)
Suitability for Heated Vape Inhalation	Designed for inhalation, though risk of respiratory irritation exists	Heated inhalation is strictly prohibited (risk of lipoid pneumonia, etc.)
Δ9-THC Residual Limit (Japan)	Other category (1ppm)	Oils and fats category (oils liquid at room temperature:10ppm)

Why Inhaling Oral Oils (MCT Oil, Vitamin E Acetate, etc.) Is Dangerous

Even though MCT oil and vegetable oils are common for culinary and oral use, heating them into an aerosol mist and inhaling them into the lungs causes oil droplets to accumulate without being absorbed or cleared, posing a risk of severe respiratory disorders (such as exogenous lipoid pneumonia). Furthermore, numerous cases of severe lung injury (EVALI) linked to inhaled products containing vitamin E acetate and similar oils have been reported in the United States.

Products listing "MCT oil," "medium-chain triglyceride oil," "edible oil/fat," or "olive oil" in the ingredients on the package are for oral use only—never put them into a vape cartridge or atomizer.

CBD, THC, and CBN Are Different Substances: Check the 2026 Regulations

CBD (cannabidiol), CBN (cannabinol), and Δ9-THC are distinct compounds treated differently under Japanese law. Product names or package labels such as "CBD Product" or "Hemp-Derived" alone cannot determine all contained ingredients or legal compliance.

CBN became a designated substance on 2026-6-1.The Ministry of Health, Labour and Welfare prohibits in principle the manufacture, import, sale, possession, and use of CBN-containing products. While procedural exceptions exist for medical and research uses, they do not permit general consumer purchase or use. Do not rely on older reviews or past articles claiming "legal" or "recommended." Source:Ministry of Health, Labour and Welfare: Designation of CBN and ProceduresThe following is a list of the most common problems with the

In addition, category-specific residual limits for Δ9-THC took effect on 2024-12-12, and any product exceeding the threshold is classified as a narcotic. These figures are product concentration standards, not intake guidelines.

Product Category	Residual Limit for Δ9-THC
Oils and fats (liquid at room temperature) and powders	10ppm
Aqueous solutions	0.10ppm
All other products (confectionery, solids, VAPE liquids, etc.)	1ppm

Product appearance or naming alone does not determine whether an item falls under the oils/fats category. You must verify the actual product category against a lot-specific Certificate of Analysis (COA). Source:Ministry of Health, Labour and Welfare: Legal Amendments and Residual LimitsThe following is a list of the most common problems with the

4 Certificate of Analysis (COA) Checkpoints Before Purchase or Use

Match Between Product Name and Batch / Lot Number:Whether the lot number printed on your actual container matches the lot number on the report rather than a generic sample certificate.
Testing Laboratory and Analysis Date:Whether the name of the third-party laboratory, date of testing, and analytical method are clearly stated.
Limit of Quantification (LOQ) and Limit of Detection (LOD) for Δ9-THC:Whether testing sensitivity is below Japan's category-specific residual limits (10ppm / 0.10ppm / 1ppm), rather than merely stating "ND (Not Detected)."
Absence of Designated Substances (Such as CBN) and Undeclared Ingredients:Whether CBN, a designated substance since 2026-6-1, is confirmed absent.

Avoid using products without verifiable lot numbers or items from unverified sources such as social media or flea-market apps, as actual contents may differ from the label.

Why "Safe Because It Is CBD" or "Side-Effect-Free Because It Is Natural" Cannot Be Assumed

The U.S. FDA highlights risks associated with CBD including liver injury, interactions with concurrent medications, pronounced drowsiness, diarrhea, and appetite changes, while noting scientific unknowns regarding long-term use and differences across intake routes (inhalation, oral, topical). Source:FDA: Risks and Unknowns of CBD ProductsThe following is a list of the most common problems with the

Research on specific prescription CBD formulations cannot be treated as proof that commercial CBD oils, gummies, or VAPE liquids improve insomnia, relieve stress, boost immunity, or aid smoking cessation. Discontinue use immediately and consult a medical professional if you feel unwell. Anyone with preexisting conditions or taking medication should consult a physician or pharmacist rather than self-medicating.