As winter approaches, we start to close our windows, turn up our heat, and warm up our cars. In other words, we are greatly increasing our chances of exposing ourselves to carbon monoxide. Working in the emergency department, it is possible that we may see multiple patients with complaints of headache and nausea on a daily basis, but picking up on subtle clues and asking certain questions may help differentiate a simple headache from something more sinister.

If a patient comes into the emergency department complaining of a headache and nausea, it is important to know whether the patient has family members who are suffering from the same symptoms. Is every member of the family at home with a headache at the exact same time? Unlike viral illnesses, where one person catches it and brings it home to spread to everyone else, headaches are not contagious. If a patient mentions that everyone at home has a headache, you may need to place carbon monoxide poisoning higher on your differential and tell everyone to get out of the house as fast as possible.1

Another thing to look out for is any patient who mentions that their pets are sick as well. If the entire family and the dog feel lethargic, the family may actually be suffering from carbon monoxide instead of a viral illness.

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If the patient says the headaches have been occurring daily or for the past several weeks, it is a good idea to ask exactly what they or their family members are doing when the headaches strike. Are they inside the house every day when a family member is turning the car on in the garage? Do their symptoms occur only when they are in a certain room? In cases like these, thorough histories can make the diagnosis much clearer.

If the patient’s history suggests exposure to carbon monoxide, asking them about carbon monoxide detectors in the home may not be enough. What a lot of people don’t realize is that unlike smoke detectors, carbon monoxide detectors stop working after 5 to 7 years, regardless of whether or not the batteries are routinely changed.2

More often than not, patients presenting with a headache are probably not going to be suffering from carbon monoxide poisoning. However, listening closely to their histories and picking up on certain buzz words may help to ensure that this important diagnosis does not go overlooked.

Jillian Knowles, MMS, PA-C is an emergency medicine physician assistant in the Philadelphia area. 


  1. New York State Department of Health. Carbon Monoxide: the Silent Killer. Revised May 2012. Accessed December 8, 2016.
  2. Fay Engineering. Carbon Monoxide: Has Your Carbon Monoxide Alarm Expired? Accessed December 8, 2016.