Sex is one of the topics that occupy both men and women the most. No wonder, then, that many myths surrounding it have evolved over the years. That’s where sex therapist Dr. Zuckerman M.D. comes in.

He is a consultant of the Between Us Clinic, which provides the PE Program—an online home exercise program for treating premature ejaculation.

We asked Dr. Zuckerman to review some common sex myths.

Oral sex is safer than intercourse

False: It is true that oral sex won’t get you pregnant, but it can easily lead to you becoming infected with STDs’. You can become infected when giving or receiving oral sex, though this is less likely when receiving. Many STDs, including chlamydia, gonorrhea, syphilis, herpes, HPV, and even HIV can be spread through oral sex. The risk can be avoided by using a condom.

Coitus interruptus is an effective way of preventing unwanted pregnancies

False: About 50 percent of men secrete a few drops of transparent fluid from their penis during sex. Some scientific literature suggests that these drops may contain semen. To find out what those drops contain, I conducted a study in which participants provided samples of the fluid, which were then examined microscopically. Dozens of examinations revealed that the dried samples did not contain even a single sperm cell.

However, when coitus interruptus is the only contraceptive method, and the man withdraws from the vagina when the ejaculatory spasms have already begun, a few drops of semen are enough to cause pregnancy, even with a quick withdrawal.

Riding a bicycle can cause erectile dysfunction

False: It is true that, while riding a bicycle, the saddle puts pressure on the perineum and reduces blood flow in that area, but unless you are spending hours each day on a bicycle, you have nothing to worry about. In addition, to reduce this risk, certain manufacturers design saddles that put less pressure on the perineum.

Size matters

True: But not in the way you think. The vast majority of patients I have seen in my career were in the normal range, which is enough to sexually please a woman. Being too small is rare, and having too large a penis can cause your partner pain. When we talk about size, circumference matters more than length. The most important thing is compatibility between partners. If the vaginal opening is too narrow in relation to the penis, the woman may experience pain.

Simultaneous orgasm is common

False: Simultaneous orgasm is a myth which does not reflect reality and is very challenging to achieve. It is normal not to reach an orgasm together during intercourse. Even if you can hold out for 20 minutes or more, your partner still may not enjoy sex or reach an orgasm that way. Only 25–35 percent of women can reach an orgasm by vaginal sex.

Blue balls are dangerous

False: When a man is aroused, there is increased blood flow to the penis and testicles. When there is prolonged sexual arousal that doesn’t end in an orgasm, some men may experience pain or a feeling of swelling. The increased blood flow builds up and puts pressure on the testicles, which can lead to pain. The good news is that it is certainly not dangerous. The pain goes away with time. You can also help to relieve the pain by ejaculating by yourself.

Elderly people don’t have sex

False: Elderly people have more sex than you probably think! The 2007 study “A Study of Sexuality and Health among Older Adults in the United States” showed that 53 percent of respondents aged 65–74 years, and 26 percent of respondents aged 75–85 years, were still sexually active! Many elderly people are in good health, which enables them to have sex, and the latest medical innovations such as Viagra help those who, in the past, were unable to have sex.

Viagra is good for premature ejaculation

False: Viagra was designed to treat erectile dysfunction. It can sometimes help to increase the time until ejaculation slightly. If a man suffers from both erectile dysfunction and premature ejaculation, I sometimes hope that the Viagra will have a positive effect on both. There are other more effective methods for a man who does not suffer from erectile dysfunction. Premature ejaculation can be treated using behavioral exercises, or it can be managed by using desensitizing sprays or through a side effect of prescribing anti-depression medication.

Erectile dysfunction is always a physical problem

False: In about 20 percent of erectile dysfunction cases, the cause is psychological. It is called “sexual performance anxiety.” When the body is in an anxious state, blood flow to the penis—which is required for an erection—may be reduced. A good indicator is morning erections. If you still experience morning erections, and you are anxious about sex, your erectile dysfunction is probably psychological.