9 Things You Didn't Know About Sperm

How savvy are you when it comes to the little swimmers?

We've all heard the rumors about sperm—pineapple, hot tubs, ladies who are allergic. But what's the truth? We consulted the experts for the facts:

# It's Fast and Furious, Right from the Start
Get this: The first moment of ejaculation contains the highest concentration of sperm, says board-certified urologist Harry Fisch, M.D., clinical professor of reproductive medicine at Weill Medical College of Cornell University.

# It Sticks Around Longer Than You Think
Sperm typically stays in your body for 48 hours after sex, however, "it can hang around for as long as five days to a week," depending on how "friendly" your cervical mucus is, says Fisch. Interestingly, cervical mucus protects sperm and helps it stay longer in the body around ovulation, when you're most fertile.

****# Lots of Sex or Masturbation Won't Lower a Guy's Sperm Count****
Don’t worry, he doesn’t have a limited supply of swimmers that he's going to use up, says reproductive endocrinologist Carrie Wambach, M.D., from Southern California Reproductive Center in Los Angeles. That said, frequent ejaculation may lower the volume, but if he generally has a normal sperm count this shouldn't make much of an impact, she says.

MORE: 14 Ways to Outsmart Sperm

# Temperature CAN Lower His Sperm Count
Apparently, his semen fluctuates with the seasons. "Sperm count tends to be lowest in summer months and highest in winter months," says Fisch, because exposure to heat lessens sperm count. Overheating can include anything as seemingly innocuous as your man having a hot Macbook on his lap or as obvious as the two of you relaxing in a hot tub. "In a Jacuzzi 104 degrees and higher, sperm count can decrease dramatically," warns Fisch. In fact, this decrease can last for months after extreme overexposure to high temps. "I tell my patients, if you're trying to have kids, don't go into hot tubs." Of course, don't assume you're totally safe from getting pregnant after you take a dip, either. "It's not birth control," he laughs.

# Pineapple Isn't Proven to Make Him Taste Better
Unfortunately, scientists haven't tested this one out yet (can somebody get on that, though?). Semen does contain fructose (naturally occurring sugar), giving it a slightly sweet taste, but there's never been a real study on the connection between foods a guy eats and the taste of his swimmers, says Fisch. However, this rumor has a ton of anecdotal evidence, so if it seems to work for your partner, we say go ahead and grab the pineapple.

****# Male and Female Sperm are Created Equal
Sperm ****either have the X or Y chromosome, but their chances of making it don’t differ, says Fisch. The idea that one type is more resilient or swims faster than the other is just a myth.

MORE: The Weird Thing That Can Mess with a Man's Fertility

# It's Super Rare to Be Allergic to Sperm
We've all heard that women can be allergic to sperm, causing inflammation or redness, but both Fisch and Wambach say that it's very, very rare to be allergic. "I'd look to other factors, like a vaginal infection, first," says Fisch. There has also been one study on a sexually transmitted allergy to Brazil nuts (where a woman had an allergic reaction to her partner's sperm after he ate the nuts). But again, cases like this are extremely rare. In the unusual case you are diagnosed as allergic, wearing a condom can prevent irritation.

# Sperm Has a Pretty Intense Journey Before the Grand Finale
It takes about two and a half months to prep all the sperm expelled in the average ejaculation. It initially forms in the testicles then moves up to the epididymis. Then fully formed sperm travels through the vas deferens and swings by the seminal vesicles where it mixes with a fluid to form semen. Finally, the prostate adds the last little bit of fluid before ejaculation.

# Your Guy's Health Affects His Sperm
"Sperm may be healthier for men under 40," says Wambach. "And they'll definitely be healthier in men who avoid things like smoking, a high-fat diet, and environmental toxins." So if you're considering starting or expanding your family, keep that in mind.

MORE: 5 Things You Should Know About Testicles (Seriously)