Glass cruet of golden-green olive oil beside a measuring spoon, olive sprig and green olives on pale limestone

Olive Oil Side Effects: Who Should Be Careful and Why

By Yusuf Elsayed, Founder of Sidr & Stone · Last updated 2 October 2026

Olive oil side effects are uncommon, and for most people they come down to amount: olive oil is a fat, so it carries calories, and large spoonfuls taken on their own can unsettle the stomach. Beyond that, the honest list is short but real. A small number of people react to olive oil on the skin, babies' skin seems to do better without it, a true allergy to eating the oil is rare and is not the same as an olive pollen allergy, and the popular "gallbladder flush" rests on a misunderstanding. People on blood pressure, diabetes or warfarin treatment have a few sensible points to check. This guide sets out who should be careful and why, with the studies behind each point, and when to speak to a GP or pharmacist.

For our own oil, see our Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml). Everything below applies to any olive oil, ours included.

The Short Answer

  • Olive oil is a food that most people eat every day without trouble; its side effects are mostly about dose and how it is used.
  • The commonest issue is energy: USDA FoodData Central lists olive oil at 884 kcal per 100 g, so one 13.5 g tablespoon adds roughly 119 calories.
  • Large amounts taken neat, especially on an empty stomach, can cause nausea, cramping or loose stools.
  • Eating-related olive oil allergy is rare. In two published cases of people allergic to both olive pollen and olives, an oral challenge with olive oil caused no symptoms.
  • On the skin, olive oil is usually a weak irritant at most, but contact allergy does occur, and a 2013 study by Danby and colleagues found that regular use weakened the skin barrier.
  • "Gallbladder flush" stones are largely soap formed from the oil and lemon juice; people with gallstone pain should see a doctor rather than try a flush.

Is Olive Oil Safe to Eat Every Day?

Yes, for most people. Olive oil eaten as part of meals is one of the most widely used fats in the world, and the side effects people search for usually reflect large neat doses, skin use or a specific medical situation rather than ordinary cooking. The useful questions are how much, how it is used, and whether anything about your own health changes the picture.

That is the shape of this guide: dose first, then the less common reactions, then the people for whom a quick conversation with a GP, pharmacist or dietitian makes sense.

Calories and Weight: The Most Common "Side Effect"

Olive oil is almost pure fat. USDA FoodData Central (SR Legacy entry 171413) lists 884 kcal per 100 g, which works out at roughly 119 calories in a 13.5 g tablespoon. Two tablespoons a day add about 240 calories; four add nearly 480. None of that is harmful in itself, but oil added on top of an unchanged diet can contribute to gradual weight gain.

The research on olive oil and health generally concerns oil that replaces other fats, not oil added to everything else. Our guide to how much olive oil per day sets out what the main studies actually used, and our olive oil calories guide gives per-teaspoon and per-gram figures. If weight is a concern, measure your usual pour once with a spoon — free pours are often bigger than people think.

Metal measuring spoons, one holding golden-green olive oil, beside a white kitchen scale and salad bowl on oak

Stomach Upset, Loose Stools and Large Doses

Fat stimulates the gut, and a large amount arriving at once — particularly a shot of oil on an empty stomach — can cause nausea, cramping, urgency or loose stools in some people. This is a dose effect, not a sign that the oil is "detoxing" anything, and it usually settles when the amount is reduced or the oil is taken with food.

The same property is why olive oil has been trialled for constipation; our guide to olive oil for constipation covers what those trials measured. If you want to try olive oil neat, start with a teaspoon rather than a tablespoon, and stop if it disagrees with you. Persistent diarrhoea, tummy pain or a change in bowel habit that lasts more than a few weeks is a reason to see a GP, not to adjust the spoon.

Olive Oil Allergy: Rare, and Different From Olive Pollen Allergy

Olive tree pollen is a common cause of hay fever where olives are grown, and it is easy to assume that pollen allergy means olive oil allergy. The published cases suggest otherwise. Unsel and colleagues (2009, Journal of Investigational Allergology and Clinical Immunology) described a 28-year-old man with olive pollen allergy who later developed itching and hives after eating olives; an open oral challenge with olive oil caused no symptoms. Racil and colleagues (2015, La Tunisie Médicale) reported a similar case in a 48-year-old woman: the challenge was positive for olives and negative for olive oil.

Two case reports cannot prove that every pollen-allergic person tolerates the oil, and allergy to the olive fruit itself is real. If you have reacted to olives, or have had a reaction you suspect was caused by olive oil, do not test it yourself at home. Ask your GP about referral to an allergy service, where any challenge can be done safely. Any swelling of the lips or throat, or difficulty breathing, needs emergency care.

Flowering olive branch with tiny cream blossoms beside a white dish of golden-green olive oil and green olives

Skin Reactions: Irritation, Contact Dermatitis and Occlusion

On the skin, olive oil is usually mild, but "natural" does not mean reaction-free. Kränke, Komericki and Aberer (1997, Contact Dermatitis) patch-tested 100 eczema patients with freshly prepared olive oil: five showed "positive" reactions, and only one was judged probably allergic. Their conclusion was that olive oil is very weakly irritant in general but can irritate meaningfully when held against the skin under a covering.

True contact allergy does happen. Isaksson and Bruze (1999, Journal of the American Academy of Dermatology) described a masseur with work-related hand eczema from olive oil, confirmed by patch and use tests; the authors noted it is considered rare, with 20 earlier cases described. Practical points: patch-test a new skin use on a small area first, avoid leaving oil under bandages or gloves, and stop if redness, itching or a rash appears. Our guide to olive oil for skin covers the wider evidence.

Babies' Skin: Why Olive Oil Is Not the Default

Rubbing olive oil into a newborn's skin is a long tradition, but two studies give reason for caution. Danby and colleagues (2013, Pediatric Dermatology) asked 19 adult volunteers to apply olive oil to one forearm twice daily for four to five weeks; it significantly reduced the integrity of the skin's outer layer and caused mild redness, while sunflower seed oil did not. The authors advised against olive oil for dry skin and infant massage.

In babies themselves, the pilot OBSeRvE trial by Cooke and colleagues (2016, Acta Dermato-Venereologica) randomised 115 healthy full-term newborns to olive oil, sunflower oil or no oil twice daily for four weeks. Both oils improved skin hydration, but showed significantly less improvement in the structure of the skin's lipid layers than no oil. The trial was not powered to show clinical effects such as eczema, and the authors simply urged caution.

The NHS guidance on bathing a baby says that if you want to use oils or lotions, check they are suitable for babies. For babies with dry skin, eczema or a family history of eczema, ask your health visitor, midwife or GP before using any oil. Our article on olive oil for baby massage looks at this research in more detail.

Folded white muslin cloth and hooded towel beside a small glass dish of golden-green olive oil on pale wood

Ears: Olive Oil Drops and a Perforated Eardrum

Olive oil is a standard home remedy for earwax, and the NHS earwax page suggests two to three drops of olive or almond oil, three to four times a day for three to five days. The same page is clear on the main caution: do not use drops if you have a hole in your eardrum (a perforated eardrum).

If you have ear pain, discharge, sudden hearing loss or a history of ear surgery, speak to a pharmacist or GP before putting anything in the ear. The NHS also advises seeing a nurse at your GP surgery if symptoms have not cleared after five days.

Gallstones and the "Liver Flush": Why We Do Not Endorse It

The "gallbladder flush" or "liver cleanse" usually involves fasting, then drinking a large amount of olive oil with lemon juice, and checking the stool the next morning for green "stones". Sies and Brooker (2005, The Lancet) analysed such stones from a 40-year-old woman who had drunk 600 ml of olive oil and 300 ml of lemon juice. They contained no cholesterol, bilirubin or calcium; about 75% was fatty acids, and the authors concluded they were "soap stones" formed in the gut. Her real cholesterol gallstones, seen on ultrasound, were removed by surgery.

There is a second, more practical risk. A large fatty load makes the gallbladder contract, and for someone who already has gallstones that can bring on an attack of pain. The NHS gallstones page describes this pain — severe, in the middle of the tummy or just under the right ribs, and lasting up to several hours — and advises an urgent GP appointment or NHS 111 if it lasts longer than 30 minutes, and 999 or A&E for sudden severe pain, a high temperature or yellowing of the skin or eyes. Olive oil in ordinary meals is a different matter; if you have been advised to eat a low-fat diet while waiting for treatment, follow that advice.

Glass measuring jug of golden-green olive oil beside halved lemons, a citrus juicer and an empty glass

Blood Pressure, Diabetes and Blood-Thinning Medicines

With medicines, the issue is usually less the oil itself than the diet change around it, because a diet change can change what your medication needs to do. In a small double-blind crossover trial, Ferrara and colleagues (2000, Archives of Internal Medicine) put 23 people with high blood pressure on diets using extra virgin olive oil or sunflower oil for six months each; daily antihypertensive dosage fell by 48% on the olive oil diet, against 4% on sunflower oil. Those reductions were made by the study doctors, not by the patients.

For type 2 diabetes, a meta-analysis by Schwingshackl and colleagues (2017, Nutrition & Diabetes), covering 4 cohort studies and 29 trials, found olive oil groups had HbA1c about 0.27 percentage points lower and fasting glucose about 0.44 mmol/l lower than control groups — modest, food-level changes. If you take warfarin, the NHS advises talking to your doctor before making any big change to your diet, because some foods, especially those high in vitamin K, can affect how it works. USDA data put olive oil at 60.2 µg of vitamin K per 100 g, about 8 µg per tablespoon. The common thread: keep your oil intake steady, tell your GP or clinic about a large change, and never adjust a dose yourself. Our guides to olive oil and blood pressure and olive oil and diabetes go further into the research.

Who Should Be Careful With Olive Oil?

Olive oil is not off-limits for any of these groups as a food, but each has a specific reason to take care:

  • People managing their weight, because each tablespoon adds about 119 calories.
  • People with sensitive stomachs or IBS, who may not tolerate large neat doses.
  • Anyone who has reacted to olives or olive oil, who should seek allergy advice before testing it again.
  • People with eczema or broken skin, especially if using oil under a dressing or glove.
  • Parents of newborns, particularly where there is dry skin or a family history of eczema.
  • Anyone with a perforated eardrum, who should not use ear drops.
  • People with gallstones or gallbladder pain, who should avoid flush regimes and large fatty loads.
  • People on blood pressure, diabetes or warfarin treatment planning a big diet change.

When to Speak to a GP or Pharmacist

Speak to a GP or pharmacist if you have a reaction you think is linked to olive oil, if a skin rash spreads or does not settle after you stop, if tummy pain lasts longer than 30 minutes, or before you make a large dietary change while on regular medicines. For a baby, start with your health visitor or GP. Call emergency services for swelling of the face or throat, difficulty breathing, or severe tummy pain with fever or yellowing of the skin.

Pregnancy is a common question too; our guide to olive oil in pregnancy covers what the research does and does not show.

The Honest Objections

"Isn't olive oil one of the healthiest foods? Why write about side effects?"

Because both things are true. Olive oil has a strong evidence base as part of a Mediterranean-style diet, and that is exactly why it is worth being clear about where its limits are. A food that is good in a salad dressing is not automatically good by the glass, on a newborn's skin or as a gallstone treatment.

"Haven't some people passed real gallstones after a flush?"

Anecdotes and single cases exist. A 2026 case report by Uma Devi and colleagues in Advances in Mind-Body Medicine describes one man with gallstones who used repeated flushes with an apple-based diet over six months. One uncontrolled case cannot separate the flush from time, diet or chance, and it does not answer the safety question for someone with stones that could block a duct. The Lancet analysis remains the clearest evidence on what most flush "stones" are.

"Does a better-quality oil have fewer side effects?"

Mostly no. Calories, the gut's response to a large dose, and allergy are the same for any olive oil. Quality matters more for freshness: an old, rancid oil tastes unpleasant and has lost much of what makes extra virgin worth buying. Our guide to telling if olive oil has gone off explains what to look for, and our guide to choosing a quality olive oil covers the label checks.

Why Sidr & Stone

This article's argument is that olive oil is a food to use well, not a remedy to take in large doses. Sidr & Stone's Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) is sold on exactly those terms: a kitchen oil, described plainly.

  • Single-estate — Sidr & Stone's olive oil comes from our own family-owned farm near Marrakech, Morocco, and we control every step from tree to bottle, with no blending across origins.
  • Rain-fed — our trees are not irrigated; they take what the season gives.
  • Organically grown — no synthetic fertilisers, pesticides or herbicides are used (not yet certified; certification is in progress).
  • Single harvest — a small, limited batch, picked when the fruit is ready; the current batch's details are on the product page.
  • Cold-pressed within hours of harvest — mechanical extraction only, with no solvents, no refining and no deodorising.
  • Unfiltered extra virgin — minimally processed, so it may show natural sediment, which is normal.
  • 100% natural — a single ingredient, olive oil, with nothing added.
  • Dark glass with a gold label — protective packaging against light.
  • 10% of profits to charity — a brand-wide commitment.
  • Fulfilment in the UK, EU, and US.

We will not tell you our oil has no side effects — no olive oil can promise that, and the points above apply to ours as much as any other. What we will say is that it is single-estate Moroccan, rain-fed, organically grown and cold-pressed within hours of harvest, and that we would rather you used a spoonful well than a glassful for a promise it cannot keep.

Sidr & Stone Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) beside a measuring spoon of golden-green oil

Frequently Asked Questions

What are the side effects of olive oil?

For most people, the main ones are extra calories and stomach upset from large amounts. Less commonly, olive oil can irritate the skin or cause contact allergy, and eating-related allergy is rare.

What happens if I take olive oil daily?

Used in meals, usually nothing unwanted beyond its calories, about 119 per tablespoon. Taken neat in large amounts, some people get nausea, cramping or loose stools, which usually settle when the dose is reduced.

Who should not use olive oil?

Very few people need to avoid it as a food. People with a confirmed allergy to olive oil, anyone with a perforated eardrum (for ear drops), and people with gallstones considering a flush should not use it in those ways; others with specific conditions should check with a GP or pharmacist.

Can olive oil cause an allergic reaction?

Yes, but rarely. Contact allergy on the skin has been reported, and olive fruit allergy exists, but in two published cases of people allergic to olive pollen and olives, eating olive oil under supervision caused no symptoms.

Can I put olive oil in my ears?

The NHS suggests olive or almond oil drops to soften earwax, but not if you have a hole in your eardrum. If you have ear pain, discharge or sudden hearing loss, speak to a pharmacist or GP first.

Is olive oil safe on a baby's skin?

The evidence advises caution. A 2013 adult study found olive oil weakened the skin barrier, and a 2016 pilot trial in 115 newborns found less improvement in skin lipid structure with oil than without, so ask your health visitor or GP first.

Where can I buy Sidr & Stone olive oil?

Our Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) is available to pre-order from the product page as a limited single-harvest batch, with fulfilment in the UK, EU, and US.

Is olive oil a medicine?

No. Olive oil is a food, not a medicine. It has a long traditional history — including being honoured in the Prophetic Sunnah — and a substantial body of modern research, particularly around polyphenols, cardiovascular health, and the Mediterranean diet pattern. It can be a worthwhile part of a healthy routine, but it does not cure diseases and is not a substitute for medical care. Be cautious of any olive oil marketed with specific disease-cure claims.

Final Thoughts

Olive oil's side effects are modest and mostly predictable: calories, a sensitive gut meeting a large dose, the occasional skin reaction, and a few specific situations — newborn skin, a perforated eardrum, gallstones and changing medicines — where care matters more. A true allergy to eating the oil is rare, and olive pollen allergy is not the same thing.

Use it as a food, measure it when the amount matters, keep it off a newborn's skin unless a professional has said otherwise, and leave the flushes alone.

Our Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) — single-estate, rain-fed and cold-pressed within hours of harvest — is available to pre-order now as a limited single-harvest batch, with fulfilment in the UK, EU, and US.

Sidr & Stone Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) with gold pourer beside bread and salad

Our extra virgin olive oil is grown organically on our own single-estate farm on the plains outside Marrakech: we control every step from tree to bottle, and no synthetic pesticides, herbicides or fertilisers are used. It is not yet certified organic — certification is in progress, and we will publish it as soon as it comes through.

Pre-Order Sidr & Stone Cold-Pressed Single-Estate Extra Virgin Olive Oil - Marrakech (500ml) — Limited Single-Harvest Batch →

References

  1. Kränke B, Komericki P, Aberer W. Olive oil--contact sensitizer or irritant? Contact Dermatitis. 1997;36(1):5-10. doi:10.1111/j.1600-0536.1997.tb00914.x. PMID: 9034680.
  2. Isaksson M, Bruze M. Occupational allergic contact dermatitis from olive oil in a masseur. J Am Acad Dermatol. 1999;41(2 Pt 2):312-315. doi:10.1016/s0190-9622(99)70372-5. PMID: 10426917.
  3. Unsel M, Ardeniz O, Mete N, Ersoy R, Sin AZ, Gulbahar O, Kokuludag A. Food allergy due to olive. J Investig Allergol Clin Immunol. 2009;19(6):497-499. PMID: 20128426.
  4. Racil H, Loukil M, Ferah Y, Cheikh Rouhou S, Chaouch N, Yaalaoui S, Chabbou A. The Pollen-Food Olive-Olive Syndrome. Tunis Med. 2015;93(5):326-327. PMID: 26578052.
  5. Danby SG, AlEnezi T, Sultan A, Lavender T, Chittock J, Brown K, Cork MJ. Effect of olive and sunflower seed oil on the adult skin barrier: implications for neonatal skin care. Pediatr Dermatol. 2013;30(1):42-50. doi:10.1111/j.1525-1470.2012.01865.x. PMID: 22995032.
  6. Cooke A, Cork MJ, Victor S, Campbell M, Danby S, Chittock J, Lavender T. Olive Oil, Sunflower Oil or no Oil for Baby Dry Skin or Massage: A Pilot, Assessor-blinded, Randomized Controlled Trial (the Oil in Baby SkincaRE [OBSeRvE] Study). Acta Derm Venereol. 2016;96(3):323-330. doi:10.2340/00015555-2279. PMID: 26551528.
  7. Sies CW, Brooker J. Could these be gallstones? Lancet. 2005;365(9468):1388. doi:10.1016/S0140-6736(05)66373-8. PMID: 15836886.
  8. Uma Devi K, Saravanan V, Vijaya Bharathi E, Mooventhan A. Effect of Six Months of Gallbladder Flush on Size and Symptoms of A Patient With Cholelithiasis: A Case Report. Adv Mind Body Med. 2026;40(2):28-31. PMID: 40982748.
  9. Ferrara LA, Raimondi AS, d'Episcopo L, Guida L, Dello Russo A, Marotta T. Olive oil and reduced need for antihypertensive medications. Arch Intern Med. 2000;160(6):837-842. doi:10.1001/archinte.160.6.837. PMID: 10737284.
  10. Schwingshackl L, Lampousi AM, Portillo MP, Romaguera D, Hoffmann G, Boeing H. Olive oil in the prevention and management of type 2 diabetes mellitus: a systematic review and meta-analysis of cohort studies and intervention trials. Nutr Diabetes. 2017;7(4):e262. doi:10.1038/nutd.2017.12. PMID: 28394365.
  11. US Department of Agriculture, Agricultural Research Service. FoodData Central: Oil, olive, salad or cooking (SR Legacy, FDC ID 171413). Accessed 2 October 2026. https://fdc.nal.usda.gov/food-details/171413/nutrients
  12. NHS. Gallstones; Earwax build-up; Warfarin; Washing and bathing your baby. Accessed 2 October 2026. https://www.nhs.uk/

Disclaimer: This article summarises published research and NHS guidance on olive oil side effects and safety at the time of writing; research findings and guidance may change, and readers should check current sources. It is general information, not personal medical advice, and does not replace advice from your GP, pharmacist, health visitor or specialist. Olive oil is a food, not a medicine, and is not a substitute for medical treatment of any condition. For any health concern, consult a qualified medical professional.

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