Mastic Gum Side Effects: Is It Safe? (2026 Safety Guide)

By Harris Hardy, founder of Gum of Gods. Updated Oct 21, 2026

Short answer: Mastic gum is generally well tolerated. The European Medicines Agency (EMA) lists its known side effects as "None known," and human trials of mastic capsules and powder reported no serious side effects. The main cautions are jaw soreness from a firm chew, allergy (the mastic tree is related to pistachio and cashew), and pregnancy or breastfeeding, where safety has not been established, so ask your doctor first.

This page is for adults who chew Chios mastic resin, or are thinking about it. It sums up what regulators and published studies say about safety, with every source linked at the bottom. It is not medical advice. If you are pregnant, breastfeeding, take medication or manage a health condition, talk to your doctor before you start. Our products are food, not medicine, and are not intended to diagnose, treat, cure or prevent any disease.

New to mastic? Start with what mastic gum is, then come back here.

Mastic gum safety at a glance

Is mastic gum safe?

For most healthy adults, the published evidence points to good tolerance, with real gaps. The most detailed regulatory review is the EMA herbal monograph on Pistacia lentiscus resin (mastic), written by EMA's Committee on Herbal Medicinal Products (HMPC) and dated 2 February 2016.^[1][2] Its companion assessment report concludes that no adverse events, serious adverse events, deaths or drug interactions had been reported from clinical trials or case studies.^[3]

The same report is honest about what is missing. It calls the safety information "limited," says tests on reproductive toxicity and carcinogenicity have not been performed, and says adequate genotoxicity studies are not available.^[3] So nobody should call mastic risk free. The fair summary is: well tolerated in the people studied so far, with too little data for pregnancy, breastfeeding and children.

Keep in mind that the EMA monograph covers mastic as a traditional herbal medicine taken by mouth as a powder, not as chewing gum. It is still the most thorough regulatory safety review of the resin we know of.

What are the side effects of mastic gum?

In the studies, very few. Here is what trials that tracked side effects reported:

• Cholesterol trial (CHIOS-MASTIHA, 2016): 179 adults were randomized to mastic or placebo for 8 weeks. The authors reported "no gastrointestinal, liver or renal adverse events" and described tolerance as excellent.^[4]
• H. pylori pilot (2010): 52 patients were randomized to one of three mastic regimens or standard therapy, with mastic taken for 14 days. "All patients tolerated mastic gum well and no serious adverse events were reported."^[5]
• Mastiha oil trial (MASTIHA-OIL, 2024): 160 adults took mastiha essential oil capsules or placebo for 8 weeks, with no gastrointestinal adverse events and no liver or kidney toxicity reported.^[6]

These studies used mastic capsules, powder or oil, not chewed gum. With whole resin, the side effect you are most likely to notice is in your jaw, not your stomach.

Can mastic gum make your jaw sore?

Yes, especially at first. Mastic is far tougher than regular gum, and any long, hard chew works the jaw muscles.

• In a 2001 study of 15 women without jaw joint problems, 40 minutes of chewing a very hard gum raised jaw pain and fatigue scores. Soft gum did not. After about 10 minutes of rest, the scores were almost back to baseline.^[7]
• In a 2020 study of 31 healthy adults, 40 and 60 minute chewing sessions caused strong fatigue that lasted up to 20 minutes. Mild pain appeared only after the 60 minute session and was gone by the first 10 minute check.^[8]
• In a 2003 study, just 6 minutes of chewing bubble gum increased jaw muscle pain in people with jaw muscle disorders (TMD).^[9]

What to do: start with one or two pieces for 10 to 15 minutes, chew on both sides, and build up slowly. Muscle tiredness that fades soon after is expected. Sharp pain, clicking with pain, locking or headaches are signs to stop and see a dentist. If you already have a TMJ disorder, ask your dentist before starting a hard chew habit. Our gum for face muscles guide has a week by week starting plan.

Can you swallow mastic gum?

You should spit it out. Chewed mastic is meant to be chewed, then thrown away or saved for later.

We found no study on what happens when someone swallows a piece of chewed mastic. What we do know:

• Mastic taken by mouth as powder or capsules, at about 1 to 2 grams a day, was well tolerated in the trials above, and that is the dose range in the EMA monograph.^[2][4]
• For chewing gum in general, a 1998 report in Pediatrics described three children who developed intestinal or esophageal blockages after swallowing gum.^[10]

Do not make a habit of swallowing it, and keep tins out of reach of young children. For context, a 25 gram Classic Pack tin is about a 30-day supply, so a normal chewing habit uses under a gram of resin a day.^[14]

Is mastic gum safe during pregnancy or breastfeeding?

Not established. The EMA monograph says: "Safety during pregnancy and lactation has not been established. In the absence of sufficient data, the use during pregnancy and lactation is not recommended."^[2] It also notes there are no fertility data.

That wording is about medicinal use, but the same data gap applies to chewing the resin. If you are pregnant, trying to conceive or breastfeeding, ask your doctor or midwife before you chew mastic.

Is mastic gum bad for your kidneys or liver?

The human data we found do not show harm, but there is not much of it.

• CHIOS-MASTIHA recorded no liver or kidney adverse events over 8 weeks at 1 to 2 grams a day.^[4]
• MASTIHA-OIL reported no liver or kidney toxicity over 8 weeks with mastiha oil capsules.^[6]
• In a 13 week rat feeding study reviewed by EMA, the highest dose lowered body weight and raised liver weight, though microscopy found no treatment-related damage in any organ.^[3]
• The EMA assessment report lists no data on safety in special populations.^[3]

If you have kidney disease, liver disease or are on dialysis, ask your doctor before using mastic.

Does mastic gum interact with medications?

None have been reported. The EMA monograph lists interactions as "None reported," and the assessment report says drug interactions from clinical trials or case studies "have not been reported so far."^[2][3] The report also notes that data on how mastic is processed in the body are very limited.^[3]

No reports is not the same as proof of no interactions. If you take any prescription medicine, check with your doctor or pharmacist before using mastic.

Can you be allergic to mastic gum?

Yes. Hypersensitivity to mastic is the one contraindication in the EMA monograph.^[2] Three facts are worth knowing:

• Plant family. The mastic tree, Pistacia lentiscus, belongs to the Anacardiaceae family.^[3] Pistachio (Pistacia vera) and cashew belong to the same family.^[11]
• A related species. In a 2024 skin test study, 26 of 27 children sensitized to pistachio also reacted to terebinth, a different Pistacia species, and all 27 reacted to cashew. The authors advised people with pistachio or cashew allergy to avoid terebinth until tests confirm it is safe.^[11] That study did not test mastic, and we found no study that did.
• Skin reactions. The only adverse reports EMA found were two case reports of allergic contact dermatitis from a medical liquid skin adhesive that contains mastic.^[3][12][13]

If you have a pistachio or cashew allergy, ask your allergist before you try mastic. If you notice itching, swelling of the lips or mouth, a rash or trouble breathing after chewing, stop and get medical help.

Can children chew mastic gum?

The EMA monograph says oral use in children and adolescents under 18 has not been established due to lack of adequate data, so it does not recommend medicinal use in that group.^[2] Whole resin tears are also small and hard. If a teen wants to try mastic, check with your pediatrician first and supervise them.

What does the EMA monograph on mastic say?

EMA's page for mastic links the final monograph (EMA/HMPC/46758/2015), the assessment report (EMA/HMPC/46756/2015) and later review documents.^[1] The key sections, side by side:

Two points to read carefully. First, the indication is based on long-standing use, not clinical proof, and it does not make mastic an "approved" drug. Second, the assessment report did not support adding mastic to the EU list of herbal substances because adequate genotoxicity data are lacking.^[3]

What is mastic studied for?

Safety is one half of the story. The research on Chios mastic that we cite on our site covers three areas, each with its source:

• Cholesterol: in CHIOS-MASTIHA, people taking 1 g of Chios mastic a day lowered total cholesterol by an average of 11.5 mg/dl in 8 weeks, compared with placebo.^[4]
• H. pylori: a 2010 randomized pilot study tested mastic against H. pylori, with mixed results; standard antibiotic therapy did better.^[5]
• Mild indigestion: the EMA lists mastic as a traditional herbal medicine for mild dyspeptic disorders.^[2]

These studies used mastic capsules or powder, not chewed gum. Study results describe the people studied and are not a promise of individual results. Our Chios mastic gum benefits hub walks through each paper.

How to chew mastic gum safely

• Warm one or two pieces in your mouth for 20 to 30 seconds before you chew.
• Start with 10 to 15 minute sessions and build up over a few weeks.
• Chew on both sides. Stop if your jaw joint hurts, clicks with pain or locks.
• Spit it out when you are done. Save a half chewed piece in a reusable gum tin if you like.
• If it sticks to crowns, braces, veneers or fresh fillings, stop and ask your dentist.
• Keep tins away from young children, hot cars and direct sun.
• Pregnant, breastfeeding, on medication, allergic to pistachio or cashew, or managing kidney or liver disease? Ask your doctor first.

What is in Gum of Gods mastic?

Our Classic Pack is Chios mastic resin with nothing added, as its product page and Nutrition Facts label show.^[14] The Classic Pack sample is 10 grams of the same resin, a good way to test the chew and your jaw before a full tin.

The flavored packs add coatings, so check each label if you have allergies:

• Peppermint Pack: Chios mastic resin coated in peppermint and stevia.^[15]
• Premium Pack: Chios mastic resin coated in pine pollen tincture and pine pollen powder.^[16]
• Maple Syrup Pack: Chios mastic resin coated in maple sugar and maple syrup.^[17]

Mastic is also a different material from supermarket gum. Regular gum base contains plastics. Ours is tree resin. See mastic gum vs regular gum and what is in regular gum base for more.

Want to make sure what you are chewing is real Chios resin? Our real vs fake mastic gum guide shows how to check any brand, and is Gum of Gods legit? covers our sourcing from the Chios Mastic Growers Association. Questions about your order or a reaction? Reach us through our Contact page.

FAQ

Is mastic gum safe to chew every day?

For most healthy adults, the evidence points to good tolerance. The EMA lists its known side effects as "None known," and trials of daily mastic capsules and powder lasting several weeks reported no serious side effects. Long-term data are limited. Start with short sessions, stop if your jaw hurts, and ask your doctor if you are pregnant, breastfeeding, take medication or have a health condition.

What are the side effects of mastic gum?

Human studies of mastic capsules and powder reported it was well tolerated, and the EMA monograph lists undesirable effects as "None known." With whole resin, the most common effect is temporary jaw tiredness or soreness from the firm chew. Allergic reactions are possible, and hypersensitivity is the EMA's only contraindication.

What happens if you swallow mastic gum?

We found no study on swallowed, chewed mastic. Mastic taken by mouth as powder or capsules at 1 to 2 grams a day was well tolerated in trials. Swallowed chewing gum has caused blockages in a few children, so spit mastic out after chewing and keep it away from young children.

Can I chew mastic gum while pregnant or breastfeeding?

Safety has not been established. The EMA monograph says that in the absence of sufficient data, use during pregnancy and lactation is not recommended. Ask your doctor or midwife before chewing mastic if you are pregnant, trying to conceive or breastfeeding.

Is mastic gum bad for your kidneys?

No kidney harm has been reported in the human studies we found. The CHIOS-MASTIHA trial recorded no gastrointestinal, liver or kidney adverse events over 8 weeks. Data are limited, so if you have kidney disease, ask your doctor first.

Can I take mastic gum with my medications?

The EMA lists drug interactions as "None reported," but data on how mastic is processed in the body are very limited. If you take prescription medicine, check with your doctor or pharmacist before using mastic.

Can you be allergic to mastic if you are allergic to pistachios?

Possibly, but it has not been studied. The mastic tree is in the same plant family as pistachio and cashew, and a 2024 study found that children sensitized to pistachio often also reacted to terebinth, another Pistacia species. If you have a pistachio or cashew allergy, ask your allergist before trying mastic.

Does mastic gum hurt your jaw?

It can at first. In a 2001 study, 40 minutes of chewing a very hard gum raised jaw pain and fatigue, which faded within about 10 minutes of rest. Start with 10 to 15 minute sessions, build up slowly, and stop if the pain is sharp, clicks or lasts.

Your next steps

1. Test the chew with the Classic Pack sample.
2. Try The Classic Pack on a monthly or 3-month plan (see our subscription policy).
3. Not sure about flavor? Read which mastic gum flavor to start with or compare with the 3-Gum Bundle.
4. Browse all mastic gum.

Keep reading

• Chios mastic gum benefits: what the research says
• Gum for face muscles: what chewing research shows
• Best mastic gum: how to choose real Chios resin
• Best mastic gum: why Gum of Gods
• Why is mastic gum so expensive?
• Best gum without a plastic gum base
• Sleep breathing stack: mastic gum, nasal strips and mouth tape
• About Gum of Gods

References

1. European Medicines Agency. Mastic (Pistacia lentiscus L., resin): herbal medicine overview page with monograph, assessment report and review documents (accessed Oct 21, 2026). https://www.ema.europa.eu/en/medicines/herbal/mastic
2. European Medicines Agency, HMPC. European Union herbal monograph on Pistacia lentiscus L., resina (mastic). EMA/HMPC/46758/2015, 2 February 2016. Sections 4.1 to 4.9 and 5.3. https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-pistacia-lentiscus-l-resin-mastic_en.pdf
3. European Medicines Agency, HMPC. Assessment report on Pistacia lentiscus L., resina (mastic). EMA/HMPC/46756/2015, 2 February 2016. Sections 1, 3.3, 3.4, 5 and 6. https://www.ema.europa.eu/en/documents/herbal-report/final-assessment-report-pistacia-lentiscus-l-resin-mastic_en.pdf
4. Kartalis A et al. Effects of Chios mastic gum on cholesterol and glucose levels of healthy volunteers: a prospective, randomized, placebo-controlled, pilot study (CHIOS-MASTIHA). Eur J Prev Cardiol 2016;23(7):722-9. doi:10.1177/2047487315603186 https://pubmed.ncbi.nlm.nih.gov/26311707/
5. Dabos KJ et al. The effect of mastic gum on Helicobacter pylori: a randomized pilot study. Phytomedicine 2010;17(3-4):296-9. doi:10.1016/j.phymed.2009.09.010 https://pubmed.ncbi.nlm.nih.gov/19879118/
6. Kartalis A et al. Effects of Chios Mastiha essential oil on cholesterol levels of healthy volunteers (MASTIHA-OIL). Hellenic J Cardiol 2024;77:63-69. doi:10.1016/j.hjc.2023.08.011 https://pubmed.ncbi.nlm.nih.gov/37634870/
7. Farella M, Bakke M, Michelotti A, Martina R. Effects of prolonged gum chewing on pain and fatigue in human jaw muscles. Eur J Oral Sci 2001;109(2):81-5. doi:10.1034/j.1600-0722.2001.00991.x https://pubmed.ncbi.nlm.nih.gov/11347660/
8. Al Sayegh S et al. Experimental pain and fatigue induced by excessive chewing. BMC Oral Health 2020;20(1):179. doi:10.1186/s12903-020-01161-z https://pubmed.ncbi.nlm.nih.gov/32600327/
9. Karibe H, Goddard G, Gear RW. Sex differences in masticatory muscle pain after chewing. J Dent Res 2003;82(2):112-6. doi:10.1177/154405910308200207 https://pubmed.ncbi.nlm.nih.gov/12562883/
10. Milov DE, Andres JM, Erhart NA, Bailey DJ. Chewing gum bezoars of the gastrointestinal tract. Pediatrics 1998;102(2):e22. doi:10.1542/peds.102.2.e22 https://pubmed.ncbi.nlm.nih.gov/9685468/
11. Celik V, Kilic FE, Tanriverdi H. Exploring terebinth cross-sensitivity in individuals with pistachio sensitivity. Int Arch Allergy Immunol 2024;185(11):1048-1054. doi:10.1159/000539324 https://pubmed.ncbi.nlm.nih.gov/38880088/
12. Worsnop F, Affleck A, Varma S, English J. Allergic contact dermatitis from Mastisol mistaken for cellulitis. Contact Dermatitis 2007;56(6):357-8. doi:10.1111/j.1600-0536.2006.01043.x https://pubmed.ncbi.nlm.nih.gov/17577380/
13. Meikle A, Vaghadia H, Henderson C. Allergic contact dermatitis at the epidural catheter site due to Mastisol liquid skin adhesive. Can J Anaesth 2012;59(8):815-6. doi:10.1007/s12630-012-9732-6 https://pubmed.ncbi.nlm.nih.gov/22653839/
14. Gum of Gods, The Classic Pack product page: raw Chios mastic resin, nothing added; 25 grams, about a 30-day supply (accessed Oct 21, 2026). https://gumofgods.us/products/the-classic-pack-include-free
15. Gum of Gods, Peppermint Pack product page: ingredients (accessed Oct 21, 2026). https://gumofgods.us/products/peppermint-pack-include-free
16. Gum of Gods, Premium Pack product page: ingredients (accessed Oct 21, 2026). https://gumofgods.us/products/premium-pack-include-free
17. Gum of Gods, Maple Syrup Pack product page: ingredients (accessed Oct 21, 2026). https://gumofgods.us/products/maple-syrup-pack