An olive oil allergy isn't unheard of, but it's extremely rare, reports the American College of Allergy, Asthma & Immunology (ACAAI). Conversely, exposure to olive tree pollen commonly causes seasonal allergic symptoms.
Olive Oil Allergy
According to the ACAAI, scientific literature contains only three reports of a serious allergy from ingestion of olives, which is classified as a fruit rather than a tree nut. In addition, it has one report of a person developing an allergy to the fruit after receiving pollen allergy shots, as well as one report of an airway illness in an olive mill worker.
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Allergic responses from skin contact with olives, such as hives or dermatitis, are also very unusual. In contrast, people who live in regions where olives are grown commonly have allergic symptoms from inhaled olive tree pollen.
Any food allergy stems from sensitivity to a protein found in the food, says the American Academy of Allergy, Asthma & Immunology (AAAAI). The infrequency of reports of an allergy to olives or olive oil is probably due to the protein content of olives being only about 2 percent, notes the ACAAI.
When the oil is extracted from olives, it's separated from the fruit solids and water, but it's conceivable that the oil may contain protein. However, among the reported incidents of allergic responses to olives, few were associated with olive oil.
If testing shows a person has an olive allergy, it's unlikely to follow that they also have an allergy to olive oil, says the ACAAI. This is because much of the 2 percent of protein content in the fruit has probably been removed during the extraction process. Nonetheless, in sensitive individuals, an allergist can test specifically for the presence of an olive oil allergy.
Olive Oil Side Effects
Reports of olive oil dangers or adverse reactions aren't found in scientific literature. It does have a mild laxative effect that can help alleviate constipation, states the International Olive Council. As long as the intake is limited to the daily recommended amount, it shouldn't produce diarrhea. The University of California Davis Olive Center advises taking 2 tablespoons per day.
Since olive oil is high in healthy fat, it's high in calories. The University of Virginia Health System School of Medicine states that 1 tablespoon has 119 calories. Does this mean that regular consumption may lead to weight gain? A June 2016 study published in the Lancet Diabetes & Endocrinology found that it may not have that effect.
In the Lancet study, a large group of participants were assigned to follow one of three dietary interventions: a low-fat diet, a Mediterranean diet with a liberal intake of extra-virgin olive oil and a Mediterranean diet with extra nuts. After five years, the consumption of fat was considerably higher in those who followed the two Mediterranean diets than those who adhered to the low-fat diet. Despite this difference, they experienced no weight gain.
Olive Oil Benefits
Research links olive oil to an array of positives, and one of the best-known benefits involves cardiovascular health. A 2018 review appearing in Endocrine, Metabolic & Immune Disorders Drug Targets evaluated studies exploring the heart-protective effects of the Mediterranean diet.
This eating plan centers on fruits, vegetables, whole grains, nuts, olive oil and fatty fish. Although all of these foods are nutrient-dense, the scientists found extra-virgin olive oil was the component most closely related to lowering the risk of heart attacks and strokes.
Research shows the main type of fat in olive oil, monounsaturated fat, may improve insulin levels and blood sugar control, notes the Mayo Clinic. A September 2017 study published in Biochemistry found another constituent of the oil, oleuropein, promotes insulin secretion. The investigative team concluded that the beneficial compound might help fight Type 2 diabetes.
Olive oil also has anti-cancer properties. In a July 2015 study featured in Molecular and Cellular Oncology, researchers tested the phenolic compound oleocanthal on human cancer cell cultures. They noted the compound caused the death of cancer cells, but it left noncancerous cells unharmed. The discovery has implications for cancer treatment, the team said.
The wellness advantages of extra-virgin olive oil include mental health. A June 2017 study published in the Annals of Clinical and Translational Neurology involved mice, but it's worth mentioning because of what it portends. The results indicated that the oil protected learning ability and memory and decreased the formation of plaque in the brain, which is characteristic of Alzheimer's disease.
Read more: Is It Good or Bad to Drink Olive Oil Every Day?
Olive Oil for Pets
Pet owners who have heard of the health effects of olive oil may wonder if it's safe for dogs. A June 2018 study published in Reproduction in Domestic Animals indicates olive oil supplementation may improve fertility in dogs.
Researchers compared the effects of the consumption of two extra-virgin olive oils containing different levels of polyphenols on canine fertility parameters. (Polyphenols are one of the main nutrients responsible for olive oil's health benefits.) The team concluded that the polyphenols have a beneficial effect on sperm in dogs.
You can also use olive oil to treat a pet's ear infection, says the Veterinary Institute of Integrative Medicine. Several drops of the oil per day in a cat's ears will eradicate ear mite infections. You may also treat mild ear infections in dogs with olive oil that has been infused with fresh garlic.
Olives for Dogs
The American Kennel Club (AKC) says dogs may eat olives in moderation. While the fruit contains nutrients important for humans, dogs fed a balanced diet don't need these extra nutrients. Nonetheless, unsalted, plain olives are an acceptable snack for your canine.
Be sure to get the pitted olives because the pits can pose health threats to dogs, warns the AKC. They can lodge in a dog's intestinal tract or block an airway and cause choking. Pits can also crack teeth. In addition, don't give a dog olives with seasonings or a garlic coating.
- American College of Allergy, Asthma & Immunology: "Does an Olive Allergy Mean I Have to Avoid Olive Oil?"
- American Academy of Allergy Asthma & Immunology: "Food Allergy"
- International Olive Council: "Olive Oil and the Digestive System"
- University of California Davis Olive Center: "Olive Oil as Medicine: The Effect on Blood Pressure"
- University of Virginia Health System School of Medicine: "How to Buy, Store and Eat Olive Oil"
- The Lancet: Diabetes & Endocrinology: "Food and Weight Gain: Time to End Our Fear of Fat"
- Endocrine, Metabolic & Immune Disorders Drug Targets: "Extra Virgin Olive Oil and Cardiovascular Diseases: Benefits for Human Health"
- Mayo Clinic: "If Olive Oil Is High in Fat, Why Is It Considered Healthy?"
- Biochemistry: "Olive Component Oleuropein Promotes β-Cell Insulin Secretion and Protects β-Cells From Amylin Amyloid-Induced Cytotoxicity"
- Molecular and Cellular Oncology: "(-)-Oleocanthal Rapidly and Selectively Induces Cancer Cell Death via Lysosomal Membrane Permeabilization"
- Annals of Clinical and Translational Neurology: "Extra‐Virgin Olive Oil Ameliorates Cognition and Neuropathology of the 3xTg Mice: Role of Autophagy"
- American Kennel Club: "Can Dogs Eat Olives?"
- Veterinary Institute of Integrative Medicine: "Ear Infection"
- Reproduction in Domestic Animals: "Effects of the Supplementation With an High-Polyphenols Extra-Virgin Olive Oil on Kinetic Sperm Features and Seminal Plasma Oxidative Status in Healthy Dogs"