The smell of pus is caused almost entirely by the type of bacteria causing the underlying infection. Most odor-causing bacteria are anaerobic in nature, which means that they don’t need oxygen to survive; instead, they generate their own sulfur compounds as they grow and spread. Sulfur is usually what’s ultimately responsible for the smell that people encounter. People who have pus-filled wounds that are populated by aerobic, or oxygen-consuming, bacteria don’t usually notice any smell. The severity of the infection might also be a factor, since the body tends to produce more pus the more widespread the condition. Personal hygiene doesn’t usually impact how pus smells, but it can in certain cases. In general, medical experts recommend that anyone who is concerned about a wound’s odor get prompt treatment, since medical intervention can stop the spread of many harmful strains of bacteria and disease.
Pus is a fluid that humans and many animals produce in response to an infection, and it’s usually one of the primary defenses in the immune system’s bid to flush harmful bacteria out of the body. It usually occurs most prolifically and most noticeably at wound sites; this can include simple issues like acne pimples as well as more severe infections like abscesses and stomach ulcer infections. When bacteria enter an open wound or delicate area of the skin, the body sends white blood cells to fight the infection. It also produces substances to help flush out the pathogens.
These substances combined with oils, dead skin cells, and other matter combined with the bacteria and white blood cells combined to form pus. On their own, these materials don’t usually have much of an odor. When people notice a stench coming from their wounds, it’s usually related more to the bacteria that the body is fighting in the first place than the composition of the mucus-like fluid itself.
Different Types of Bacteria
The type of bacteria driving the infection is usually the primary cause of any smell. This explains why some pus-filled wounds have virtually no odor at all, and why others have a very strong smell. The more sulfur-producing bacteria present, the more likely the smell of pus will be strong and offensive. In many cases, strong-smelling pus can indicate that the condition is more contagious and thus more likely to spread, since in general the concentrated bacterial volume is higher.
Issues of Severity
It’s often also true that severe infections smell worse than more minor ones. This is particularly the case when strong odors are coming out of what otherwise seem to be small injuries or wounds. The higher the concentration of sulfur and other foul-smelling microbial byproducts, the worse the stench is likely to be.
Role of Hygiene
The smell of pus doesn't generally have anything to do with one's hygiene or cleanliness. People are often tempted to more aggressively clean or sterilize wounds that small bad, but this isn’t usually a good idea since abrasive cleansers can aggravate the infection site. Even very clean individuals can acquire an infection with malodorous pus. Many forms of infection affect the skin when bacteria enter pores, hair follicles, or oil glands. These are relatively common and affect most people from time to time. More serious infections can occur after an injury or illness, and these are more likely to require medical treatment.
Still, hygiene can play a role. People who don’t keep the infection site clean and protected are more likely to contract secondary infections, which can often involve anaerobic strains, and compound wounds often smell worse due to the combined force of the bacteria. Even here, though, it’s not as much hygiene that’s actually causing the smell; it’s simply contributing to it.
It is normal for pus to have a smell to some extent, but any serious infections should be checked by a doctor. The factor that determines a serious infection isn’t usually so much whether pus has a smell, but rather the extent of other symptoms. Open wounds that are widespread or very large, or those accompanied by a fever, should generally be investigated by a doctor. In some cases antibiotics will be needed in order to kill the offending bacteria and restore health.