Frankincense Oil Safety: Side Effects, Pregnancy & Precautions

General Safety Profile

In the aromatherapy and cosmetics literature, frankincense essential oil is generally characterized as having low acute toxicity when used at recommended dilutions. The International Fragrance Association (IFRA) does not list frankincense oil among compounds with mandatory use restrictions, and it does not appear on the EU's list of 26 allergens requiring declaration in cosmetic products.

That said, the biological activity of frankincense compounds is not trivial. A 2019 study published in Complementary Therapies in Clinical Practice documented pronounced anti-proliferative and pro-apoptotic effects of frankincense essential oil on human breast cancer cells in vitro, with significant cytotoxic activity at relatively low concentrations — findings that underscore why this level of biological potency makes appropriate dilution a practical necessity, not merely a precaution. Undiluted essential oils can cause sensitization or irritation precisely because their active compounds are concentrated.

For most healthy adults, frankincense oil used at appropriate dilutions in aromatherapy, skincare, and massage is considered safe. The precautions detailed below apply in specific circumstances or to specific modes of use.

Dilution Guidelines

Essential oils must always be diluted in a carrier oil before skin contact. The appropriate dilution percentage depends on the application, the size of the area being treated, and the individual's sensitivity. The figures below follow the guidelines established by the Alliance of International Aromatherapists (AIA) and Robert Tisserand's widely used reference work on essential oil safety.

• ◆ Facial application: 0.5–1%. For a 30ml facial serum, that is 3–6 drops of essential oil total. The face is more sensitive than the body, and facial skin is thinner. Start at 0.5% for new users or sensitive skin types.
• ◆ Body application (massage, lotion): 2–3%. For a 30ml body blend, that is 12–18 drops. This range is appropriate for healthy adults applying to non-sensitive body areas.
• ◆ Spot treatment (localized areas only): Up to 5%. This is for small areas — a joint, a scar, a localized skin concern — and should not be applied over large surfaces. Do not use at this dilution on the face.
• ◆ Diffusion (inhalation): 3–5 drops in a standard 100ml ultrasonic diffuser. Diffuse in ventilated spaces; do not run a diffuser continuously for more than 30–60 minutes at a stretch.
• ◆ Bath: Essential oils do not disperse in water without an emulsifier. Mix 5–10 drops into a tablespoon of unscented bath gel, whole milk, or a purpose-made bath dispersant before adding to the tub.

Full application guidance — including carrier oil selection and methods for different uses — is covered in our how to use frankincense oil guide.

Pregnancy and Breastfeeding

The safety of essential oil use during pregnancy is an area where caution is warranted and the evidence base is limited. Ethical constraints prevent the kind of randomized controlled trials on pregnant populations that would definitively establish safety parameters, which means the field relies heavily on precautionary principles, case reports, and extrapolation from pharmacological data on individual compounds.

Frankincense oil is generally listed as one of the essential oils that may be used with caution during the second and third trimesters at low concentrations (0.5–1% or lower), but most aromatherapy safety guides recommend avoiding all essential oils during the first trimester when organogenesis is occurring. This includes frankincense.

The active compounds in frankincense oil — particularly the terpenoids — are lipophilic, meaning they can cross biological membranes including the placental barrier, at least when exposure is sufficient. The clinical significance of this at typical aromatherapy doses is not well established, but it is a reason for conservative use.

During breastfeeding, similar caution applies. Bioactive compounds from essential oils can appear in breast milk. Low-level diffusion in ventilated spaces is generally considered lower risk than direct topical application.

The consistent recommendation from qualified aromatherapy practitioners and organizations including the National Association for Holistic Aromatherapy (NAHA) is to consult a healthcare provider or certified aromatherapist before using essential oils during pregnancy or while breastfeeding. Do not apply essential oils directly to the abdomen during pregnancy.

Children and Pets

Children metabolize essential oil compounds differently from adults. Lower dilutions are appropriate across all applications: a maximum of 0.5–1% for children over 2 years, and 0.25% for very young children. Essential oil use is not recommended for infants under 3 months. Keep essential oils out of reach of children; ingestion of even small quantities can be dangerous.

For pets, frankincense oil requires significant care. Cats in particular lack the liver enzymes (glucuronosyltransferases) needed to metabolize many aromatic compounds, making them vulnerable to toxicity from essential oils that are safe for humans. Dogs can tolerate some essential oil diffusion but are far more sensitive than adult humans. Never apply essential oils directly to pets without veterinary guidance. If diffusing around pets, ensure they can leave the room and that ventilation is good.

Drug Interactions

The research on essential oil–drug interactions is underdeveloped relative to herb–drug interactions for oral botanicals, largely because the systemic absorption of topically and aromatically administered essential oils is typically lower. However, some interactions are documented or theoretically plausible.

Frankincense oil's constituents include compounds with demonstrated effects on certain cytochrome P450 enzymes, which are central to drug metabolism. If you are taking medications with a narrow therapeutic window — anticoagulants, immunosuppressants, antiepileptics, or certain cardiovascular drugs — it is worth discussing essential oil use with your prescribing physician, particularly if you are considering any topical application over large areas.

People taking blood-thinning medications (including aspirin, warfarin, or newer anticoagulants) should exercise particular caution, as some terpenoid compounds have mild anticoagulant or antiplatelet properties. This is a theoretical concern at aromatherapy doses but warrants transparency with your healthcare provider.

Allergic Reactions and Patch Testing

Contact sensitization to frankincense oil is uncommon but documented. People with known sensitivities to other Burseraceae resins (including balsam of Peru or other oleoresins), or with a history of reactions to fragrances, are at higher risk. A patch test before first topical use is a sensible precaution regardless of sensitization history.

To patch test: dilute frankincense oil to 2% in your intended carrier, apply a small amount to the inner forearm, and cover lightly. Wait 24–48 hours. Redness, itching, swelling, or a rash indicates sensitivity; discontinue use.

Research into the effects of frankincense essential oil on mucosal tissue — including a 2022 study in Molecules examining the effects of frankincense essential oil on oral cavity tissues — highlights that mucous membranes are considerably more sensitive to essential oil compounds than intact skin. This has direct implications for any use near the eyes, mouth, nose, or other mucous membranes: even well-diluted formulations should not be applied to or near these areas, and undiluted oil should never come into contact with them.

If frankincense oil contacts the eyes, flush immediately with plain vegetable oil (not water) to dilute the essential oil, then rinse with water. Seek medical advice if irritation persists.

Internal Use: Why We Don't Recommend It

Some essential oil brands market frankincense oil as safe for internal use — typically as drops in water or under the tongue. The Frankincense Oil Institute does not recommend internal use of frankincense essential oil, and this position aligns with the guidance of the National Association for Holistic Aromatherapy (NAHA), the Alliance of International Aromatherapists (AIA), and most certified clinical aromatherapists.

The reasons are straightforward. Essential oils are highly concentrated — a single drop can represent the bioactive compounds from a large quantity of plant material. The gastrointestinal tract, particularly the mucous membranes of the esophagus and stomach, is sensitive to direct contact with undiluted or even lightly diluted terpenoids. The mucosal sensitivity documented in frankincense oil research is directly relevant here.

The compounds associated with frankincense's studied therapeutic properties — particularly boswellic acids — are not actually present in significant quantities in the essential oil. They are large, non-volatile molecules that remain in the resin and do not distill into the oil. If the goal is supporting a therapeutic benefit associated with boswellic acids, the appropriate vehicle is a standardized Boswellia extract taken orally — a supplement form that has been the subject of clinical trials. Our boswellic acid guide covers this distinction in detail.

Essential oil ingestion accidents are among the more common calls to poison control centers involving natural products. If accidental ingestion of more than a few drops occurs, contact a poison control center immediately.

Storage and Shelf Life

Frankincense essential oil has a relatively good shelf life compared to many other essential oils, primarily because its dominant monoterpene compounds are somewhat more stable than those of citrus oils. Unopened, stored correctly, frankincense oil typically remains stable for 2–3 years. Once opened, 1–2 years is a reasonable working life if storage conditions are appropriate.

Key storage requirements:

• ◆ Temperature: Store below 25°C (77°F), away from heat sources and direct sunlight. A cool, dark cabinet is ideal. Avoid bathrooms where temperature fluctuates with hot showers.
• ◆ Light: UV light accelerates oxidation. Quality frankincense oil comes in amber or cobalt glass — never clear glass. Keep lids tightly closed between uses.
• ◆ Oxygen exposure: Half-fill bottles are more vulnerable to oxidation. If you have a large bottle that is running low, consider transferring to a smaller bottle to reduce headspace.
• ◆ Signs of degradation: A sour, turpentine-like, or noticeably harsh smell indicates the oil has oxidized. Oxidized essential oils are more likely to cause skin sensitization and should not be used topically. When in doubt, discard.

Understanding what quality frankincense oil looks and smells like when fresh is also the best defense against purchasing oxidized or adulterated product. Our quality standards guide covers GC/MS testing, adulteration markers, and what to look for in a reputable supplier.