Oregano Oil: 6 Major Side Effects You Must Know

Written by Ravi Teja Tadimalla

Oregano oil is the essential oil of oregano (the Italian herb). While the herb is popular for its use in a variety of cuisines, including salad dressings and pizzas, the essential oil is known for its potent antimicrobial properties (1).

The important chemical compounds in oregano oil can serve as a boon to many. But if taken in excess, oregano oil can cause certain undesirable side effects.

What Are The Side Effects Of Oregano Oil?

Oregano oil may cause skin allergies in certain individuals. It may also lead to gastric distress and hypoglycemia. Some reports suggest that the oil can also cause miscarriage and must be avoided by pregnant women.

1. May Cause Allergies

Though oregano oil is usually well-tolerated, it can cause skin allergies in certain individuals (2). These effects could be more pronounced in oregano oil supplements as such products do not require strict approvals by the US FDA (Food and Drug Administration).

Individuals allergic to plants in the Lamiaceae family tend to be allergic to oregano as well. The other plants in this family include basil, marjoram, sage, mint, and lavender (3).

In some people, oregano oil can also cause skin irritation in concentrations as low as 3-5%. Inhaling the oil may not have such effects (4).

2. May Cause Gastric Distress

Intake of oregano oil may lead to gastrointestinal distress (2). However, there is very limited research as to why that occurs. Hence, please consult your doctor before ingesting the oil.

3. May Lead To Hypoglycemia

The carvacrol in oregano oil could be responsible for this effect. In rat studies, it was found to show reductions in serum glucose levels (5). Though this could be good news, individuals who are already on medications to lower blood sugar may experience hypoglycemia (excessively low blood sugar levels).

Oregano oil may also be one of the few essential oils that can impact glucose sensitivity (6). If you are already on diabetes medications, oregano oil may further accentuate the effects.

4. May Cause Miscarriage


A herbal infusion containing oregano was reported to cause abortions in pregnant women (7). The herbal infusion contained various other ingredients too, so it was hard to determine if oregano was the sole culprit.

Other reports also discuss the possibility of herbal infusions causing miscarriage. Also termed as herbal abortion, it is a process involving the consumption of a series of herbs to induce miscarriage deliberately (8). Oregano oil may be one such herb.

There is less research directly linking oregano oil to miscarriage. However, please exercise caution as the oil may have abortifacient effects (9).

5. May Lead To Cardiac And Respiratory Collapse

Oregano contains another compound, thymol, which may lead to cardiac and respiratory collapse. The compound may also lead to central hyperactivity, convulsions, and even coma. Though these effects are rare, it is important you be aware of them (10).

6. May Interact With Certain Drugs

Given its hypoglycemic effects, oregano oil might interact with diabetes medications. There is no research to support this, though. If you are taking diabetes medications, please check with your doctor before you consume oregano oil.

Oregano oil may also interfere with the absorption of zinc, iron, and copper. Those taking these supplements must consult their doctor before ingesting oregano oil. There is very little research to support this.

There is no doubt oregano oil is beneficial to human health. But taking it in excess can have detrimental effects.

What Is The Ideal Dosage Of Oregano Oil?

There is very less information available about the ideal dosage of oregano oil. Most supplements and essential oils have dosages specified by the manufacturers. These dosages take into account the oil’s most potent compounds, including thymol and carvacrol.

Please do not exceed the dosage specified on the container. If you are looking for the ideal dosage for yourself, please consult your doctor.

Also, there is limited information on if you can actually ingest oregano essential oil. Do check with your health care provider. Some sources state that you must take a week-long break after using oregano oil every three weeks. The evidence backing this up is not solid. Your health care provider must be able to guide you better.

When Should You Visit A Doctor?

As discussed, there is less information on the safety of oregano oil upon ingestion. If you experience any of the following symptoms, please visit your doctor:

  • rashes
  • headaches
  • fatigue
  • stomach distress
  • difficulty swallowing
  • muscle pain

The best way to avoid these symptoms is to consult your doctor. Also, the oil is available in most health stores. Remember to go for a reputed brand and follow the manufacturer’s instructions.


Oregano oil has important benefits, thanks to its beneficial compounds. Most of the problems with the oil surface with excess use. Hence, a doctor’s advice is crucial.

Otherwise, you can use the oil on a regular basis to avail its benefits. Using it along with a carrier oil can give you better results and minimize the risk of side effects.

Have you used oregano oil before? How did you like it? Tell us your experiences by sharing a comment in the box below.

Frequently Asked Questions

Can you take oregano oil with antibiotics?

There is less information focusing on the possible interactions oregano oil may have with antibiotics. Please consult with your doctor.

How long can you take oregano capsules?

You can take the capsules every day. Sticking to the right dosage is key. Also, check for any adverse reactions you may face.


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Ravi Teja Tadimalla is an editor and a published author. He graduated from SRM University, Chennai, and has been in the digital media field for over six years. He has a Professional Certificate in Food, Nutrition & Research from Wageningen University. He considers himself a sculptor born to chip away at content and reveal its dormant splendor. He started his career as a research writer, primarily focusing on health and wellness, and has over 250 articles to his credit. Ravi believes in the great possibilities of abundant health with natural foods and organic supplements. Reading and theater are his other interests.