Limonene
Smells like orange — as aerosol, it oxidises to allergenic follow-up products.
⚠ Sounds harmless — it isn't
Limonen riecht nach Orange und ist als Lebensmittel- und Kosmetik-Inhaltsstoff zugelassen — als Aerosol oxidiert und pyrolysiert es allerdings zu allergenen und reizenden Folgeprodukten, die in der Lunge tiefer wirken als auf der Haut.
At a glance
- Also known as
- D-Limonen · Citrusterpen
- CAS number
- 5989-27-5
- Toxicity
Medium
- Carcinogenic
- Not classified for cancer
- In cigarette smoke
- In vape aerosol
- in Citrus-, Frucht- und „cooling“-Liquids; beim Erhitzen Bildung reizender Pyrolyseprodukte
What is Limonene?
Limonene is a monoterpene, the characteristic odorant of citrus peels. D-Limonene (the natural mirror-image isomer) is the main component of essential oils from orange, lemon and bergamot. The IARC classifies D-limonene as Group 3. Widely used in food, cleaning products and cosmetics, in vape aerosols it appears in citrus and fruit flavours.
Why is Limonene in cigarettes?
Limonene is used in vape flavours for citrus, fruit and partially „cooling“ profiles. Unlike pure flavour taste, limonene has a characteristic property: it oxidises easily in air and on heating — when the bottle has been open a few weeks or the coil gets unusually hot, limonene oxidation products with their own biological action form.
What Limonene does to your body — short term
Limonene itself is acutely barely irritant. The problematic substances are its oxidation products — especially limonene 1,2-oxide and carvone. These follow-up products are potent contact allergens and can trigger irritation and airway symptoms in sensitised individuals. Studies (Karlsson et al., 2007) show that about 6 to 11 percent of the population react allergically to limonene oxidation products.
What Limonene does long term
Chronic limonene inhalation from vape aerosols is toxicologically still young research. Hints from animal studies suggest kidney stress at high doses — in humans the kidney effect is less relevant than in male rats (species-specific α-2u-globulin mechanism). The bigger concern in vape application is allergenic oxidation products plus pyrolysis to reactive aldehydes — limonene at high coil temperatures can release acrolein and acetaldehyde.
Where else do you know Limonene from?
You know limonene as the main smell of freshly peeled oranges or lemons and as the main component of natural citrus cleaning products (eco all-purpose cleaners). In cosmetics and food flavouring, limonene is extremely widespread. EU cosmetics regulation requires allergen labelling at elevated limonene concentrations, because sensitisation via skin contact is common.
How it compares
The ACGIH recommended value for D-limonene at workplaces is 30 ppm (170 mg/m³) as an 8-hour shift value. Vape aerosol inhalation is below this in absolute terms, but oxidation and pyrolysis products aren't captured in customary limits — and these are exactly the actual risk.
Workplace exposure limit: ACGIH TLV-TWA 30 ppm (170 mg/m³)
Related substances
These substances you want out of your body.
Flamy walks you through quitting, step by step.
Download the Flamy app