Semen typically has a faint smell due to a mixture of chemicals, such as citric acid and calcium. It may also smell slightly sweet, as it contains fructose. A strong, fishy odor might indicate an infection, while a very sweet smell may be a sign of diabetes.

Sperm make up just 1% of semen.

The fluids that make up the other 99% contain chemicals that have a slight smell. Some changes in smell are normal, whereas others could indicate a health condition.

Semen is slightly alkaline, with a pH ranging from 7.2 to 7.8. This is slightly less alkaline than seawater or baking soda. Semen typically smells like other substances with a similar pH.

Some people report a smell that is similar to bleach or ammonia. Others may notice a sugary smell because semen contains fructose, a sugar also found in fruits. Semen also contains magnesium and calcium, which can give it a slightly metallic or salty smell.

A person can notice slightly different smells at different times. Semen is primarily made up of water, so the smell is usually faint. Some people may not even notice a smell.

The smell of semen can also change if it mixes with other substances, such as urine or sweat. If semen combines with acidic vaginal fluids, this can affect the smell.

Semen can also smell different when it dries. Dried semen tends to have a stronger, more noticeable smell.

Prolonged or significant changes in the smell of semen may point to an underlying medical condition. Some smells that could signal a problem include:

  • Very strong smell: Bacteria and other germs can change the way semen smells. If semen has a foul and overpowering odor or gets worse with time, it may be a sign of an infection. It may also indicate an issue with the prostate, which produces substances present in semen.
  • Sweet smell: Normal semen can smell slightly sweet because of the fructose it contains. But semen that has a particularly sweet odor could be an early warning sign of diabetes. One older study suggests that men with diabetes may have more sugar in their semen, giving it a sweeter smell than usual.
  • Fishy odor: Fishy-smelling semen may indicate a sexually transmitted infection.

There is currently no high quality research linking dietary changes to lasting changes in the way semen tastes or smells.

But just as food can change the way a person’s sweat or skin smells, it may also temporarily change the smell of semen.

People may want to try avoiding strong-smelling foods, such as fish. It may also help to avoid foods that can change the smell or color of other bodily fluids, such as asparagus.

Everyone’s semen smells differently. Some people may even notice the smell changing from time to time or with shifts in diet, exercise, rest, and other lifestyle factors.

It is best to see a doctor if:

  • semen suddenly smells foul
  • semen smells very sweet
  • there is blood in the semen
  • ejaculation becomes painful
  • urinary issues occur, such as incontinence or more frequent trips to the bathroom at night
  • the genitals become itchy
  • there is unusual discharge from the penis
  • bumps develop on or around the genitals

Semen has a faint smell that varies from person to person. Some factors can change the smell of semen, such as when it mixes with urine or vaginal fluids.

Diet is not thought to change the smell of semen in any lasting way.

Lasting smell differences or very strong odors can be a sign of an underlying medical condition. For example, a strong foul or fishy smell can be a sign of infection or a change in prostate function.

See a doctor if these changes occur.