What Is Semen? 12 Frequently Asked Questions

Semen—also known as cum or ejaculate—isn't the same thing as sperm. This whitish bodily fluid comes out of the penis when a person ejaculates. Its purpose is to help sperm move outside of the body, where it can enter the vagina during sexual intercourse and fertilize an egg.

You may have questions about this bodily fluid, which is an important part of reproduction. Here are some of the most commonly asked questions about semen, including what it's made of and how the body makes it.

What’s the Difference Between Semen and Sperm?

Semen and sperm are not the same thing. Sperm are tadpole-shaped, microscopic cells that are part of semen. The job of the sperm is to fertilize an egg to create an embryo. The sperm is carried along by fluid that's produced by different male sex organs to get to an egg.

What Is Semen Made Of?

The seminal fluid contains chemicals that make semen liquid-like, allowing sperm to move more freely. The prostate is a gland that produces seminal fluid. The seminal vesicles, or two tubes in the pelvis, provide fructose. This sugar gives sperm the energy it needs to get to an egg.

Sperm also contains different proteins, as well as small amounts of:

• Cholesterol
• Glucose
• Lactic acid
• Potassium
• Selenium
• Sodium
• Urea

What Is the Purpose of It?

The purpose of semen is to carry sperm through the penis and outside of the body. Semen that enters the vagina allows sperm to move through the fallopian tube, where it can meet an egg.

A zygote is a fertilized egg, which includes half of the genetic material from the sperm and half of the genetic material from the egg. It can implant inside the uterus, where it eventually can develop into an embryo. An embryo develops into a fetus, which generally grows for 40 weeks before childbirth occurs.

Where Is Semen Stored?

Sperm are stored in the epididymis. This tube moves mature sperm from the testicles to a structure called the vas deferens. The prostate then makes seminal fluid, which mixes with sperm to create semen. The prostate doesn't store semen but instead creates the fluid that allows it to move through the penis during ejaculation.

Does Pre-Ejaculate Contain Sperm?

Pre-ejaculate, which is also known as pre-cum, comes out of a penis during sexual activity. This fluid contains barely any viable sperm. What sperm is found in pre-ejaculate is generally immobile, meaning it's not likely to result in pregnancy.

Pre-ejaculate is released from glands called Cowper glands. "The clear secretion protects sperm from the acid environment of the urethra and the vagina, as well as lubrication to some degree," Michael Reitano, MD, the physician in residence at the male health service Ro, told Health.

Can You See Sperm?

You can't see sperm: They're about 0.05 millimeters (mm) long, which is 1/600 of one inch. Sperm are constantly dividing in the testicles, which make millions of these cells every day.

How Much Is Typically Ejaculated?

The average amount of semen released during ejaculation averages between 1.5 to 5 milliliters (ml). This is the equivalent of about 1 teaspoon (tsp). There are nearly 20 to 150 million sperm in 1 ml of semen.

What Does Semen Smell and Look Like?

"Semen can typically have a slight ammonia or bleach-like odor," said Dr. Reitano. "Semen can have a slight change in odor or taste with changes in food, meaning eating asparagus may result in a similar change in the odor of semen as noted with urine."

Foul-smelling semen could be a sign of a sexually transmitted infection (STI). Yellow or green semen can be another sign of an STI, said Dr. Reitano. Semen that's red can be the result of an enlarged prostate, infection of the prostate, or irritation or injury to the urethra.

Can You Be Allergic to It?

Semen allergies are possible but rare. An allergic reaction is usually localized and causes redness or swelling at the point of contact, such as the mouth, vagina, or anus. Research has shown that the proteins in semen can trigger the allergic reaction.

A partner can also be allergic to their partner's semen if they have an allergy to a certain drug, such as antibiotics, their partner has consumed. The allergen can build up in the semen and be absorbed into the blood when it comes into contact with a body part.

Is Semen Good for Your Skin?

Semen has emerged as a trend in skincare, but it's probably not going to benefit your skin in any way. "Semen doesn't have any inherent components that are bad by nature," said Dr. Reitano. It's still best to stick to skincare products that can clear up acne breakouts.

How Long Do Sperm Live?

Sperm can live for five or less days inside the vagina, waiting for an egg to appear so they can fertilize it. Sperm can't survive very long outside the body.

"If ejaculation occurs in a hot tub with chemicals, the sperm can live no more than a few seconds. If it's deposited into a bath of warm water that is approximately 98 degrees, [they] may live for a few minutes," said Dr. Reitano. "If it is deposited into the air and onto a hard surface, it will live until the semen is dry. The sperm dies when that occurs."

Does the Body Ever Stop Producing It?

The male reproductive system continuously produces sperm, but it isn't always viable as you age. Sperm produced by people older adults are more likely to be abnormal than the sperm of younger people.

Sperm production slows down as people get older. Semen production is highest in people in their 20s but can decrease slowly at any point onward.

A Quick Review

There are quite a few things to know about semen. Semen is an important component of the male reproductive system. This whitish bodily fluid carries sperm from outside the body. Semen can enter the vagina, where it can fertilize an egg during sexual intercourse.

It's important to see a healthcare provider if you notice changes to the quality of your semen, including color or odor. Color changes or a foul odor can be signs of an infection or injury.