Dear Doctor: Can olive oil be used topically to aid healing?

Dear Reader: Olive oil has been used since ancient times as a cosmetic and to aid skin healing. The ancient Egyptians used it as an anti-wrinkle potion; the Romans used it as a moisturizer after bathing. To this day, olive oil is used widely in many countries to treat and prevent multiple skin conditions.

Now let's look at the evidence.

The purported benefit of olive oil may come from its fatty acid composition, predominantly oleic acid, but also palmitic acid and linoleic acid. These fatty acids have been thought to have both anti-fungal and anti-bacterial properties.

Oleic acid, a monounsaturated fat, has been shown to penetrate the upper layers of skin, where it permeates between the cells -- seeming to suggest that it's an effective moisturizer. Anecdotal evidence might seem to bear that out, but note that oleic acid has been found to actually increase water loss across the epidermis, countering the notion that it can help lock in the skin's moisture.

In a 2013 study published in the journal Pediatric Dermatology, researchers studied volunteers who applied six drops of olive oil to their forearm twice daily for five weeks. They found that the skin treated with olive oil not only lost water, it also experienced a reduction in skin thickness and integrity, and in some people caused a local reaction. The authors surmised that olive oil's disruption of the skin may allow for penetration of allergens and increased inflammation of the skin's layers.

Some people use olive oil in an attempt to mitigate stretch marks induced by pregnancy. The evidence for that is sketchy as well. In a 2012 study published in Complementary Therapies in Medicine, 50 women who were 18 to 20 weeks pregnant applied olive oil twice daily to their abdominal skin, massaging it in gently each time, keeping this practice up until they had delivered their baby. A control group of 50 women applied nothing to their abdominal skin. Although researchers did find some decrease in severe stretch marks among those who used olive oil topically, they found no overall significant difference in stretch marks between women who used olive oil and those who didn't.

One place where olive oil may hold potential is in its treatment of diabetic foot ulcers. A 2015 study published in the Journal of Diabetes and Metabolic Disorders showed a significant improvement of healing and shrinking of ulcers with use of olive oil among people with grade 1 or grade 2 diabetic ulcers (the least serious of the grades, which progress to grade 5). Complete ulcer healing occurred after 4 weeks in 73.3 percent of those who had olive oil placed over the ulcer versus 13.3 percent who didn't. This healing may be related to olive oil's potential to dry the lesion, which is linked to its propensity to remove water from the skin.

As for other skin conditions, some case reports have suggested that olive oil may reduce acne and symptoms of impetigo, but no controlled studies have been done.

So the evidence for olive oil on its own as a topical agent is not convincing. Further, it may even cause skin irritation, so I wouldn't recommend it as a moisturizer, especially for infants. But because of olive oil's ability to penetrate the skin, it could potentially be helpful in combination with another agent. As for its potential in healing skin ulcerations in the lower legs and feet, further study is needed.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: We just moved from Miami to northern Michigan, and even though my daily routine hasn't changed and I'm not on any new medications, I have begun to get a nosebleed every few weeks. Should I be worried?'

Dear Reader: If you had reported the onset of nosebleeds on a daily or even biweekly basis, then we would be having a different discussion. But you have recently moved from a climate that is warm and moist to one that, in winter, is cold and dry, and this can cause quite a bit of stress to delicate nasal tissues. Add in the effects of the heaters and furnaces that are pumping hot, dry air into homes and offices, and you've set the stage for the occasional nosebleed.

Why? A look at the inner workings of the nose will help explain.

Our noses have two main jobs. They not only serve as airways that filter, moisten, and either warm or cool the air we breathe, they are also our scent organs. Behind the visible portion of the nose that draws in air lies a wonderfully complex series of chambers and canals known as the sinus cavities. These are covered with a specialized lining called the mucosa, which includes numerous mucus glands that keep all the inner surfaces moist.

When cold or dry air causes the nasal membranes to dry out enough that they crack, the result is a nosebleed. This is most common in areas where winters are cold or summers are hot and dry. Because nasal membranes gradually become less robust over time, older adults can be more susceptible to nosebleeds than those who are younger. Individuals on blood-thinning drugs are also at greater risk.

Fortunately, there are a few steps you can take to lessen your chance of another nosebleed. First, try a little tenderness. When you need to blow your nose to clear it of mucus, do so gently. Instead of abruptly trumpeting full force into a tissue, use the minimum amount of gradual pressure needed to clear your nasal passages.

Using a humidifier, particularly in the bedroom as you sleep, gives your mucus membrane a boost. Just be sure to stay vigilant about keeping the humidifier clean, as moist air is basically a welcome mat for fungus. A dab of a water-based ointment inside each nostril will also help to keep things lubricated.

If you do get another nosebleed, don't panic. Lean forward (if you lean back, you wind up swallowing blood) and lightly pinch your nostrils together near the bridge of your nose. This puts pressure on the vessel that's bleeding and the flow should stop. Give it five minutes and then gently release.

If your nose is still bleeding, pinch again and go for another five minutes. In most cases, bleeding will stop within 10 to 15 minutes. If you nose is still bleeding after 20 minutes, it's time to see a doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: BHT, a preservative in a lot of food products, really does a number on me. One serving of food with BHT, and I wake up with terrific pain in my head and right eye, upset stomach, chills and fever. How common are such allergies, and how can I avoid these reactions?

Dear Reader: BHA and BHT, short for butylated hydroxyanisole and butylated hydroxytoluene, are antioxidants used to preserve a wide array of foods, including snack foods, meats, butter, chewing gum and rice, as well as cosmetic products and medications. Both BHA and BHT prevent oxidation of oils, helping prevent ingredients from becoming rancid and, in some foods -- such as breakfast cereals, baked goods and potato chips -- helping maintain product crispness.

These antioxidants rarely cause allergic reactions. This was first officially evaluated more than 25 years ago in a placebo-controlled trial involving two patients who had a history of hives; the patients were first exposed to BHA and BHT via foods in their diet, then to a placebo. The elimination of these two components from their diet led to a reduction in the frequency and the severity of their hives.

In 2007, a study published in Toxicology and Applied Pharmacology identified the mechanism for the allergic reaction. In studying rats given BHT, researchers found an increase in immediate skin allergies, linking it to an allergic response that caused a type of white blood cells, known as mast cells, to release the chemicals histamine and leukotrienes. These chemicals caused an allergic response in the skin.

Questions remain, however, about the effect of the chemicals and the allergic response to them. Although the chemicals could theoretically induce nasal allergies and asthma in those already susceptible, researchers have yet to establish proof of increased asthma or nasal allergies with BHA.

BHA in particular has been singled out as potentially increasing the risk of cancer. This worry stems from studies in rats and hamsters in the 1980s. One notable study showed that rats fed diets with up to 1 to 2 percent of BHA had increased cancers of the stomach. Of those that ingested a diet with 1 percent BHA, 20 percent developed cancers of the stomach; of those that ingested a diet of 2 percent BHA, 100 percent developed cancers of the stomach.

In the United States, the highest amount of BHA that is approved in foods is 0.02 percent, which is significantly less. Overall, some studies in rats have shown an increased risk of cancer, and others have shown a decreased risk in cancer.

When it comes to humans, researchers have found little evidence of a potential cancer link. In a study published in 2000 in Food and Chemical Toxicology, researchers in the Netherlands used a dietary questionnaire to ask 120,000 men and women between the ages of 55 and 69 about their dietary intake of BHA and BHT. After six years, the authors found no increase in stomach cancer among those with higher BHA/BHT intake.

When it comes to cosmetic products, the very low percentages of BHA and BHT found in those products have not been linked to cancer.

Your reactions to BHT appear to be a form of allergy. Obviously, the best thing you can do is simply avoid this chemical. While writing this, I looked at the foods in my house to determine whether they might contain BHA or BHT and found only one item. So it seems you could eliminate your home exposure to BHA and BHT by reading labels.

Going out to eat is obviously trickier, so you'll have to be diligent. Stay away from clearly processed foods, and stick to whole, plant-based or healthful foods. Pay special attention to sauces. If a food has a sauce, make sure to ask your server if it was made from totally fresh ingredients or if it might contain foods with additives, specifically BHA or BHT.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)