9 Surprising Things To Know About Semen

Semen—also known as ejaculate, spunk, and a host of other, less printable nicknames—is fluid that carries sperm cells and is ejaculated from the penis. Other than sperm, what else is in there? Why does it look and smell different sometimes? And is it just a myth that it's great for your skin? To answer these and other questions, we talked to a men's health specialist, who shared some seriously fascinating facts.

There's More to Semen Than Sperm

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

"The prostate fluid contains chemicals that make semen more liquid-y so the sperm can swim more freely," said Michael Reitano, MD, a physician in residence for the men's health service Roman. "The seminal vesicles [two tubes in the pelvis] provide fructose, a sugar that gives spermatozoa the energy it needs to swim all the way to the female egg." Altogether, these components make up semen.

It Has Actual Nutrients

Dr. Reitano said that sperm contains vitamin C, B12, ascorbic acid, calcium, citric acid, fructose, lactic acid, magnesium, zinc, potassium, sodium, fat, and hundreds of different proteins. But don't quit your daily vitamin just yet. "The quantity of actual nutritional components is tiny," Dr. Reitano said, and most of semen is simply water.

What about the calorie count? "If the actual nutritional elements are added—meaning all the fats, proteins, and carbohydrates—then a ¾ teaspoonful of semen may provide little more than a few calories of nutrition."

A Lot Less Comes Out Than You Might Think

The average amount of semen released during ejaculation averages between 1.5 to 5 milliliters, the equivalent of about one teaspoon, according to MedlinePlus. But this stuff packs a punch—there are nearly 20 million to 150 million sperm in an average milliliter of semen.

Semen Quality Changes With Age

True, men can produce sperm throughout their entire lives. But it isn't always viable. Dr. Reitano said that sperm produced by people over age 52 were more likely to be abnormal than the sperm of younger people. Sperm production slows down as people get older, according to MedlinePlus. "Semen production is highest in men in their 20s or so, but can decrease slowly starting at any point from that age onward," Dr. Reitano said.

Pre-Ejaculate Is a Different Fluid

Precum, or the pre-ejaculate fluid that comes out of a penis during intercourse, contains barely any viable sperm, according to the American Pregnancy Association.

"Most of the evidence leans toward pre-ejaculate containing no sperm, or only very tiny amounts of sperm," Dr. Reitano said. "What sperm is found [in precum] tends to be poorly formed and immobile. Men are considered infertile if they have too little sperm, so the tiny amounts that may be found in pre-ejaculate are extremely unlikely to result in pregnancy."

So what's the point of precum? "Pre-ejaculate is a slightly basic secretion released from glands called Cowper glands," Dr. Reitano said. "The clear secretion protects sperm from the acid environment of the urethra and the vagina, as well as lubrication to some degree."

It's Not Supposed To Smell Bad (or Turn Yellow)

Stinky semen could be indicative of a larger issue. "Foul-smelling semen can be a sign of an infection, possibly a sexually transmitted infection. STIs may also be at work if the semen takes on a yellow or green color," Dr. Reitano said. "On occasion, a broken blood vessel in the urethra or prostate can make semen appear brown or reddish."

What is semen supposed to smell like? "Semen can typically have a slight ammonia or bleach-like odor," Dr. Reitano added. "Anecdotally, 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."

Semen Helps Sperm Live Longer

Sperm can live three to five days inside the vagina, just waiting for the egg to appear so they can fertilize it and do what nature intends them to do, according to the American Pregnancy Association.

But outside of the body, semen can't survive very long. "If ejaculation occurs in a hot tub with chemicals, the sperm can live no more than a few seconds. If it is deposited into a bath of warm water that is approximately 98 degrees, [they] may live for a few minutes," Dr. Reitano said. "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."

Semen Facials Are an Actual Thing

For whatever reason, semen seems to be the latest trend in skincare. But Dr. Reitano said that while it's likely safe, it's probably not going to benefit your skin in any way. "Semen doesn't have any inherent components that are bad by nature," Dr. Reitano said. Stick to acne products to clear up those breakouts instead.

You Really Can Be Allergic to It

Unfortunately, semen allergies are possible, Dr. Reitano said. "This is a rare condition but it exists. The allergic reaction is usually localized and causes redness or swelling at the point of contact—usually the vagina." To be precise, it's the proteins in semen that trigger the allergic reaction, according to an overview from 2020 in The Journal of Allergy and Clinical Immunology: In Practice.

"Another way a partner can be allergic to their partner's semen is if she has an allergy to a particular food or antibiotic, for example, and the male partner has eaten the food or is taking the antibiotic to which she is allergic," Dr. Reitano added. "The allergen accumulates in the male's semen, and when it is placed in the vagina, the allergen is absorbed into the bloodstream. The female partner may develop widespread hives or worse." Yikes!

A Quick Review

There are quite a few things to know about semen. Semen is an important component in the reproductive system, and now you know more about what is inside of it, the nutrients it contains, the possible allergic reaction some people may have to it, and the role it plays in the reproductive system.