We often take for granted our ability to smell, but your nose can do more than just let you know when it’s time to take out the trash or lead you to your favorite restaurant. It can also sniff out health problems to help you live longer and healthier. In fact, your ability to smell, or lack thereof, or other nasal sensations can even predict a life-threatening condition.

Here are eight nasal signs and symptoms that can reveal specific things about your overall health:

1. Smelling Something Weird Could Predict a Stroke

Some people are born with a stronger sense of smell that allows them to pick up on more scents than others. But being able to smell something like smoke or fish when there isn’t any around sounds rather bizarre and, in fact, may be a sign of a stroke or seizure. According to the American Academy of Neurology, the condition where you detect smells that aren’t actually present is called phantosmia. The phantom smells are usually unpleasant chemical-like odors, but they may differ from person to person.

Phantosmia (also called olfactory hallucination) usually means something’s wrong with the area of the brain where smell is processed. It can be triggered by temporal lobe seizures, head trauma, or even brain tumors. If you have similar smell malfunctions, you should contact a doctor right away to deal with potential stroke.

2. The Smell of Ammonia Could Mean Bad Kidneys

One of the most important jobs of the kidneys is to filter out waste from the blood to be excreted in the form of urine. If the kidneys aren’t functioning well, though, waste may build up in the body, which can produce an ammonia-like smell detected in the back of the nose or a metallic taste in the mouth.

This symptom usually occurs at stage 4 or 5 chronic kidney disease (CKD), a progressive loss of kidney functions, and may accompany others such as kidney pain, changes in urine color, and fatigue—so the smell of ammonia probably won’t be the first sign of kidney trouble if that is the case.

3. Fading Sense of Smell Could Mean an Early Death

The most common cause of smell loss, or anosmia, is a stuffy nose from a cold. However, a continuously fading sense of smell could be a sign of deteriorating brain health. A 2014 study conducted by researchers from the University of Chicago Medical Center found that not being able to detect certain odors was associated with a higher risk of dying within five years. In a Swedish study of adults aged 40 to 90 who were followed for 10 years, those with a poor sense of smell had about a 20 percent increased risk of mortality within 10 years.

4. Frequent Nosebleeds Could Indicate Heart Problems

Nosebleeds are common, but they are usually brief and harmless. Frequent, non-stop nosebleeds, however, could be a sign of some serious heart health conditions such as high blood pressure or congestive heart failure. Frequent or prolonged nosebleeds can also be caused by a hypertensive crisis—a sudden, rapid increase in blood pressure—which may be accompanied by a severe headache, shortness of breath, and anxiety. If you’re having frequent nosebleeds, you may want to talk to your doctor even if you can stop them fairly easily.

5. Poor Smell Detection May Be a Sign of Alzheimer’s

Having a poor sense of smell could signal the early stages of Alzheimer’s disease according to a Harvard Medical School study. During the study, participants with elevated levels of telltale proteins that are found in the brains of Alzheimer’s patients performed worse on an odor-identification test. They also lost more brain cells, due largely to the fact that the disease kills brain cells, which includes those crucial to the sense of smell.

6. Black Snot Could Mean a Dangerous Fungal Infection

If your snot is the color of tar, you’ve probably got a problem. Black mucus can be the result of smoking cigarettes; residual particles from the smoke and burnt substances can turn snot dark.

The other possibility is that there is a life-threatening fungal infection called acute fulminant fungal rhinosinusitis, a rather rare condition that usually only occurs in very ill people with compromised immune systems, such as cancer patients undergoing chemotherapy. Often, microscopic fungal spores are too tiny and few to be seen with the naked eye at all. Emergency surgery and antifungal medication are necessary before the fungus invades the eyes or brain.

7. A Cold Nose Could Indicate Too Much Stress

If the weather is cold, you may simply need more rest, yet nose temperature is also linked to brain activity. A study from the University of Nottingham, United Kingdom, suggests that a cold nose could be a sign that the brain is overworked and blood is being diverted to the brain from other places. The brain needs a constant and sufficient supply of blood (delivering oxygen and nutrients) to keep it functioning properly. After all, the brain controls all body functions. So, it’s not surprising that blood would be diverted from extraneous areas, such as the nose, in order to supply more crucial organs.