Dear Doctor: What exactly is the connection between birth control pills and breast cancer? Is the evidence credible? If so, why do so many women still take them -- and so many doctors prescribe them?

Dear Reader: The reason women take them, and doctors prescribe them, is quite simple: Hormonal contraceptives (birth control pills) are an effective means to prevent pregnancy. They are widely available, used by an estimated 140 million women worldwide. This equates to 13 percent of women ages 15 to 49.

The hormones in these pills are either estrogen and progesterone or progesterone alone. Concern about the possible connection to breast cancer centers on the fact that many types of cancer are stimulated by estrogen and progesterone. So hormone-containing pills could theoretically increase the risk for breast cancer.

Older studies assessing this risk have shown either a very mild increase in risk or no increase. A 1996 article in the journal Lancet combined data from 54 studies in 25 countries assessing the risk of breast cancer among women who had used hormonal contraception of various types, including pills, injectables and IUDs. Overall, the study found a small increased risk -- 7 percent -- of breast cancer among women who had ever used hormonal birth control. Among current users, it found a 24 percent increased risk. In women who had stopped taking hormonal birth control for either one to four years or five to nine years, it found a 16 percent and 7 percent increased risk, respectively. No increased risk was found among women who had stopped taking hormonal birth control more than 10 years prior.

Then came a 2017 study in the New England Journal of Medicine of 1.8 million women, ages 15 to 49, in Denmark. The women were followed for an average of about 11 years and, over that timeframe, 11,517 were diagnosed with breast cancer. Those who had ever used hormonal birth control (oral or implantable) had a 20 percent increased risk of breast cancer when compared to women who had never used it. Those who had used it for less than one year had a 9 percent increased risk over never-users, and those who had used hormones for more than 10 years had a 38 percent increased risk.

The risk did not vary based on the type of oral contraceptives, nor was there a difference in risk between oral contraceptives and hormone-containing implantable birth control. When the authors analyzed the risk posed specifically by oral contraceptives, they found an increased risk of 24 percent compared to non-users of any hormonal contraceptive.

A natural question is: What if a woman has an increased risk of breast cancer already? A 2013 study combined data from eight studies of women who were carriers of a BRCA gene mutation that increases the risk for breast cancer. It found a 21 percent increased risk of breast cancer among oral contraceptive users, meaning the risk was no different for women with a higher risk of breast cancer.

Here's another way to look at it: The number of breast cancers caused by hormonal contraceptives is one extra breast cancer case per year (above what already would be expected) for every 7,690 women.

In short, although oral contraceptives may slightly increase the risk of breast cancer, the risk isn't enough to recommend that women stop using a reliable, largely safe method of birth control.

(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: How does the flu virus spread? I've always thought it was mostly from coughing, which contaminates the air and the surfaces we touch. But now I've heard that people who are sick actually breathe the virus out. Should I be wearing a mask to protect myself?

Dear Reader: One of the more challenging points to get across regarding the flu has been just how contagious a sufferer is, and how early into a bout of the illness that contagion begins. Now comes research that makes understanding (and acting on) this information all the more crucial.

You're correct that the assumption has been that it's by coughing that we pump aerosolized droplets of moisture, which contain the flu virus, into the air and onto the surfaces around us. We've known for some time that these droplets can hang in the air for up to several hours and can live on hard surfaces for several days. But the results of a recently published study by scientists at the University of Maryland's School of Public Health show that by simply breathing, a person who is sick with the flu is exhaling the virus.

The researchers examined the mechanics of how 142 university students with confirmed cases of influenza sent the virus into the air around them. The participants in the study sat in front of a device that could measure various sizes of the aerosolized droplets they dispersed while coughing, sneezing, talking or breathing. In 218 sessions that lasted 30 minutes each, it was revealed that close to half of the airborne droplets that contained the flu virus were collected in the absence of coughing. Since the participants rarely sneezed, the takeaway was that people with an active infection are dispersing the virus into the air around them when they breathe.

An earlier study from the University of Hong Kong concluded that half of flu infections within households are passed along via aerosolized droplets. The study also looked into your question of whether wearing a surgical mask would prevent infection. The answer echoes the findings of several similar studies -- basically, no. Though masks may slightly reduce risk by screening out the largest droplets, they are not effective against the fine aerosolized mist from the breath. According to the Centers for Disease Control and Prevention, the people who really should be wearing facial masks are individuals who are ill.

It's important to note that the University of Maryland study did not tackle the specific question of how the flu is transmitted. Still, the findings do suggest that, even in the absence of coughing, people with the flu can send the virus into the environment around them.

All of which leads to advice that physicians have been giving -- and which patients have been ignoring -- for generations. And for emphasis, we're putting it into a paragraph of its own:

Stay home when you're sick.

Not only do you really and truly need to rest in order to give your body the best shot at recovering from influenza, but venturing forth while you're actively ill puts everyone around you at risk.

(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: What can I do about persistent, intermittent rectal itch? I keep the area clean and dry and have tried numerous over-the-counter anti-itch medications, which seem to work for a short time before becoming ineffective. My primary care physician gave me an anti-fungal prescription (clotrimazole with betamethasone), which my dermatologist said was unwarranted. Your suggestions?

Dear Reader: Kudos to you for being willing to talk about this annoying symptom that most people don't like to acknowledge, even to their doctors. Be assured: Anal itching (pruritus ani) is a common condition affecting 1 to 5 percent of the population. It's four times more common in men than in women and occurs predominantly between the ages of 40 and 70.

As for why the condition occurs, it's generally due to small amounts of fluid stool that irritate the anal region. This may be because the stool itself is loose or because the anal sphincter is abnormally relaxed, allowing leakage. In both cases, fecal material irritates the area beyond the sphincter and causes itching, leading to excessive wiping or scratching of the region. A 1982 study found that 50 percent of people with anal itching normally had loose stools and that 41 percent lost small amounts of stool at least one day a week. Of note, coffee has been found to relax the sphincter in 70 percent of people with the condition.

Other factors can lead to pruritus ani as well, with fungal infections accounting for 15 percent of episodes. People with diabetes, those who are taking medications that suppress the immune system and those who have used multiple courses of antibiotics are at increased risk of this type of infection.

Bacterial infections can also cause anal itching. So can chemicals from soaps, creams or wet wipes, either through direct irritation or through an allergy to these products. Hemorrhoids and psoriasis can be factors too.

The first step in treating pruritus ani is to eliminate practices that irritate the anal region. Start by washing the area -- without soap -- to remove any retained material. This can be done with a bidet, or through showering or bathing. Other steps: Use softer, more absorbent toilet paper to make wiping less irritating; make sure the anal area is dry before putting on underwear; and use a zinc oxide cream to help heal the anal area and create a barrier against further irritation.

As for food and drink, not only has coffee been associated with anal itching, other foods and beverages have also been implicated. These include beer, cola, caffeinated tea, chocolate, citrus foods and drinks, tomatoes, chocolate, peanuts and grapes.

The antifungal preparation that your primary care doctor recommended includes a mixture of antifungal and steroid compounds. The steroid betamethasone eases the itching, and the clotrimazole cream acts against any existing fungal infection. However, strong steroid creams can cause skin thinning in the anal region, potentially leading to further irritation and itching.

In summary, take a hard look at the foods and drinks you're consuming; remove irritating soaps or wet wipes; use water to clean the anal area; keep the area dry; and use a zinc oxide cream to help healing. By following these strict habits, you just might be able to rid yourself of this annoying symptom.

(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.)