Ammonia can cause symptoms in two very different ways: breathing in ammonia gas causes immediate burns to your eyes, skin, and airways, while a buildup of ammonia in your blood (hyperammonemia) gradually damages brain function and produces neurological symptoms ranging from mild confusion to coma. The specific symptoms you experience depend entirely on which type of exposure is involved and how severe it is.
Symptoms of Breathing In Ammonia Gas
Ammonia is a colorless gas with a sharp, unmistakable smell. It shows up in cleaning products, fertilizers, refrigeration systems, and industrial settings. When you inhale it at high concentrations or get it on your skin, the damage is fast and obvious. The CDC lists the following symptoms of exposure to elevated levels of ammonia gas:
- A burning feeling in the nose, throat, lungs, and eyes
- Coughing, sometimes producing white or pink fluid
- Skin blisters, redness, or pain
- Swelling and narrowing of the throat
- Temporary or permanent blindness
- Frostbite, if exposed to the liquefied form
Even brief exposure to concentrated ammonia gas can injure lung tissue. If you notice a strong ammonia smell and start coughing or feel a burning sensation, move to fresh air immediately. Pink or blood-tinged fluid when coughing is a sign of serious lung damage and requires emergency care.
Symptoms of High Ammonia in the Blood
Your body produces ammonia constantly as a byproduct of breaking down protein. Normally, the liver converts it into a harmless substance called urea, which leaves through your urine. When the liver is too damaged to keep up, or when a rare genetic condition prevents this conversion, ammonia accumulates in the bloodstream and crosses into the brain.
Normal blood ammonia in adults sits below 30 micromoles per liter. An increase to just 100 micromoles per liter can alter consciousness, and levels around 200 are associated with coma and seizures. That’s a narrow margin, which is why even modest liver problems can produce noticeable neurological symptoms.
Once ammonia reaches the brain, it increases levels of glutamate, the brain’s primary excitatory chemical messenger. This overstimulates certain receptors and disrupts the normal balance between excitation and inhibition. The brain tries to neutralize ammonia by converting it into glutamine inside specialized cells, but when ammonia floods in faster than these cells can process it, brain function deteriorates.
How Symptoms Progress in Stages
Doctors grade the neurological effects of ammonia buildup on a scale from 0 to 4, known as the West Haven Criteria. Understanding these stages helps you recognize early warning signs before they become dangerous.
At grade 0, changes are so subtle that only you or people close to you might notice. Short-term memory slips, slower reaction times, and mild difficulty concentrating are typical. Standard neuropsychological tests can pick up these changes, but they’re easy to dismiss in everyday life.
Grade 1 brings mild confusion or forgetfulness, mood swings (sometimes euphoria, sometimes anxiety), trouble with basic arithmetic, and difficulty with fine motor tasks like writing. Many people at this stage assume they’re just tired or stressed.
By grade 3, symptoms are impossible to ignore: severe drowsiness, inability to recognize where or when you are, amnesia, and involuntary jerking movements. One hallmark sign at this stage is asterixis, sometimes called “liver flap.” If you extend your arms and bend your wrists back, your hands will flap involuntarily in a rhythmic pattern. While asterixis is strongly associated with liver failure, it can also appear in other conditions that disrupt brain metabolism.
Grade 4 is coma, a complete loss of consciousness.
Symptoms in Newborns and Children
Babies born with urea cycle disorders, genetic conditions that prevent the liver from processing ammonia properly, can develop dangerously high ammonia levels within the first few days of life. Because both breast milk and formula contain protein, ammonia builds up quickly once feeding begins. Warning signs in newborns include refusal to feed, extreme sleepiness or unresponsiveness (lethargy), and seizures. Without treatment, this can progress to coma. These symptoms often appear so early that they’re detected in the hospital, but parents bringing a newborn home should watch for feeding difficulties paired with unusual sleepiness.
In older children, the normal upper limit for blood ammonia is below 50 micromoles per liter. Symptoms of a milder urea cycle disorder may not appear until a child is older and eating more protein, at which point they might show irritability, repeated vomiting, or episodes of confusion that come and go.
Physical Signs That Accompany High Ammonia
Because high blood ammonia most commonly results from liver disease, you’ll often see liver-related symptoms alongside the neurological ones. Jaundice, a yellowing of the skin and eyes, develops when the liver can’t properly filter bilirubin from the blood. When bilirubin levels climb high enough, bile breakdown products accumulate and cause intense itching all over the body.
Other visible signs of liver dysfunction include spider angiomas, tiny networks of blood vessels visible just under the skin surface, and a tendency to bruise or bleed easily. Some people develop a reddish-purple rash of small dots or larger patches that indicate bleeding beneath the skin. Nausea, vomiting, and abdominal pain are common as well.
One distinctive sign worth knowing about is a particular breath odor sometimes called fetor hepaticus. It’s been described as musty, oddly sweet, and pungent, compared to everything from rotten eggs and garlic to freshly mown hay. The smell comes primarily from sulfur compounds the failing liver can’t clear. Ammonia itself plays only a minor role in this odor, despite common assumptions.
Why Blood Ammonia Tests Can Be Tricky
If your doctor orders a blood ammonia test, the accuracy of the result depends heavily on how the sample is handled. Ammonia levels in a blood sample rise on their own over time as red blood cells and platelets release ammonia through chemical reactions in the tube. One study found that samples with higher platelet counts showed ammonia concentrations 62% higher than low-platelet samples, even when analyzed immediately. For this reason, blood drawn for ammonia testing needs to be chilled on ice and processed quickly. Certain types of blood collection tubes can also interfere with the results. If your ammonia level comes back unexpectedly high and you don’t have obvious symptoms, a repeat test with careful specimen handling may give a more accurate picture.
Common Causes of Elevated Blood Ammonia
Liver cirrhosis is the most frequent cause in adults, particularly when it progresses to a condition called hepatic encephalopathy, which is essentially the brain dysfunction caused by the liver’s failure to clear toxins. Acute liver failure from drug reactions, viral hepatitis, or overdose can also spike ammonia levels rapidly. In children, urea cycle disorders are the primary concern. Less common causes include severe kidney disease, certain medications, overwhelming infections, and gastrointestinal bleeding (which releases large amounts of protein into the gut for bacteria to convert into ammonia).
High-protein diets don’t cause dangerous ammonia levels in people with healthy livers. But for someone with existing liver damage, even a moderate increase in protein intake can tip ammonia levels into the symptomatic range.