Dear Doctor: My granddaughter's college offers "morning-after" pills via vending machine. Using these pills without a doctor's prescription and oversight can't possibly be safe, can it?

Dear Reader: Between 2006 and 2010, one out of every nine women of reproductive age used some form of emergency contraception -- often when other forms of contraceptives had failed. Although the subject raises both religious and ethical questions for some people, the reality is that so many women have already been safely treated with emergency contraception by doctors that some forms of the drugs are now available over-the-counter.

Oral emergency contraception works by delaying a woman's ovulation, thus lowering the likelihood that sperm will fertilize an egg. Pregnancy rates among 20-something couples is 30 percent if intercourse occurs one to two days prior to ovulation. If intercourse occurs at any random point in a woman's cycle, the overall chances of getting pregnant are only 4 to 6 percent. Studies of Plan B (levonorgestrel), the medication provided via vending machines at some campuses, show an overall chance of pregnancy of 2.6 percent among women who've taken the drug. So in reality, the drug is only about 50 percent effective in most cases.

Note that, if a woman is obese or overweight, the drug is even less effective. Obese women (those with a body mass index of 30 or higher) were four times more likely to become pregnant after taking Plan B than those with a healthy body mass index. Overweight women (BMI of 25 to 29.9) were two times more likely to get pregnant after taking Plan B than normal-weight women.

Plan B has other limitations as well. For maximum effectiveness, it must be used within 72 hours after intercourse, and it doesn't work as well among women taking some seizure medications or St. John's wort.

That said, the physical side effects of Plan B are relatively minor; they include nausea, vomiting, headache and breast tenderness. Among women who do become pregnant after taking Plan B, there has been no evidence of altered growth or development of the fetus. There is also a low likelihood of birth defects. However, Plan B's biggest downside is that it just doesn't work very well. Plan B may give a false sense of security that a pregnancy won't occur, so women should understand that they have other choices for emergency contraception.

The prescribed medication ulipristal acetate (Ella) has an efficacy rate of about 66.7 percent and can delay ovulation by five days. Further, the drug has been used in Europe for many years and has been FDA-approved in the United States since 2010. The side effects are similar to those of Plan B.

The most effective form of emergency contraception is the insertion of a copper intrauterine device (IUD) by a doctor. This is 95 percent effective at preventing pregnancy, and in a study of 1,013 women who had this device placed in the first five days after intercourse, the pregnancy rate was 2 in 1000.

Of course, many doctors don't provide the copper IUD, and one could argue that a woman may not be able to see her doctor in a timely enough fashion to get an IUD or other form of emergency contraception. Some women may even be embarrassed to see a doctor about emergency contraception.

So, although Plan B may not be as effective as other forms of emergency contraception, it is still moderately effective and quite safe. Those who are obese or taking medications that interact with Plan B should look for other options.

(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 kind of eye protection should be worn during a solar eclipse? I live in a part of Nebraska where the upcoming eclipse on Aug. 21 will be total.

Dear Reader: The path of totality for this eclipse, which arcs its way from Oregon to South Carolina, will cut a diagonal right through your state. As Californians living 900 miles south of the closest point of totality, we envy you.

We put our astronomy hats on and, with an assist from NASA, learned that the last total solar eclipse in North America occurred on July 7, 1972. (The wait for the next one won't be quite so long -- it's coming on April 8, 2024, and will be visible from Texas to Maine.)

This year, if you have clear skies and live in the Lower 48, you'll get to experience at least a partial eclipse. And that means that for the two to three hours the eclipse lasts, you must take precautions to protect your eyes and eyesight.

A solar eclipse occurs when the orbits of the moon and the sun align in a way that the moon blocks any part of the sun. In your area, you'll get the rare spectacle known as totality, which is when the moon completely blocks the sun's face. During up to 2 minutes 40 seconds of sudden nighttime -- the light will be about as bright as a full moon -- the solar corona, which is the flaming, roiling crown of the sun's atmosphere, will be revealed.

During totality and only then, NASA scientists say it's safe to look directly at the eclipse. (NASA has a great interactive map on its website that pinpoints the arc of totality.) However, before and after totality, you risk damage to your eyes and to your eyesight if you look directly at the sun.

That's due to something called solar retinopathy, which happens when sunlight floods the retina, located at the back of the eyeball. This causes the rods and cones, the light-sensing cells that make vision possible, to release a flood of communication chemicals which can damage the retina. It's often painless, so you don't even realize damage is being done. And remember -- even at 99 percent of totality, the sun's rays can cause retinal damage.

Here, courtesy of NASA and (deep breath) the American Astronomical Society, the American Academy of Ophthalmology, the American Academy of Optometry and the National Science Foundation, are eclipse-viewing guidelines:

-- The only safe way to look at the partially eclipsed sun is through special solar filters like "eclipse glasses," or through handheld solar viewers.

-- Homemade solar filters and ordinary sunglasses, no matter how dark, are NOT safe for looking at the sun.

-- Never use a camera, telescope, binoculars or other optical device, whether filtered or unfiltered, to look at the un-eclipsed or partially eclipsed sun. They will concentrate the solar rays, which will enter your eye and cause serious injury.

-- Full instructions, including the only four certified manufacturers of eclipse glasses, are available at eclipse2017.nasa.gov/safety. We strongly recommend you read (and share) this information.

(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: I know that doctors say there's no connection between breast cancer and deodorants/antiperspirants. But has this ever been tested?

Dear Reader: First, we should explain the difference between deodorants and antiperspirants because each has chemicals that cause concern. Deodorants, as the name implies, remove the odor from axillary (underarm) sweat by killing, or stopping the growth of, bacteria. Antiperspirants decrease the amount of sweat excreted by sweat glands. Stick and roll-on products often contain a combination of deodorant and antiperspirant, and their wide use is intertwined with modern living -- they remove the pungent odors that can act as barriers to human interaction.

More than 50 percent of breast cancers occur in the upper outer quadrants of the breast, near the underarm. The concern many people have is that chemicals applied to the underarm may find their way to the breast tissue. The thinking goes like this: Because many breast cancers are stimulated by estrogen -- and underarm products often contain estrogenlike chemicals -- such products may stimulate breast cancers.

It's true that deodorants contain phenol compounds, such as triclosan, which have estrogenlike properties, and antiperspirants often contain aluminum, which activates estrogen receptors. Further, the parabens used as preservatives in underarm products also have estrogenlike properties.

Lastly, aluminum chloride and aluminum chlorohydrate, which are often found in antiperspirants, have been shown to decrease BCRA-1 gene function in the breast and also decrease many of the repair genes within the breast. This could increase susceptibility to breast cancer -- again, so the thinking goes.

But do all these factors add up to actual risk? A 2002 study looked at 813 women diagnosed with breast cancer between 1992 and 1995 and compared them with 793 women without breast cancer. The authors asked the women whether they had used deodorant/antiperspirants -- and if so, how regularly -- and whether they had used the products within one hour after shaving. Some people suspect that shaving creates minute cuts in the skin that allow the underarm products to do more damage. The authors found no difference in the rates of underarm-product use between those who had breast cancer and those who didn't.

Another study, this one in 2003, asked 437 women diagnosed with breast cancer about their antiperspirant/deodorant use and underarm shaving. Those who shaved and used underarm products the most were diagnosed with breast cancer 12.6 years earlier on average than those who did this infrequently. Those women who began shaving and using underarm products before the age of 16 had a diagnosis of breast cancer 9.6 years earlier than those who began this practice after age 16.

Note, however, that both studies were retrospective, meaning that they looked back after the disease had already occurred. What would be more convincing is a prospective study -- with similar populations of people who use and don't use underarm products -- that follows participants for many years. An estimated 90 percent of people use antiperspirants/deodorants in the United States, so a prospective type of study may finally lay to rest the link between underarm products and breast cancer.

(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.)