Common viruses that cause cold
flu or
stomach flu can cause nausea and headache. There may be other associated signs like runny nose, diarrhea, fever, body aches which may be suggestive of a viral illness. Migraine can cause nausea, severe headache and there may be extreme sensitivity to light. Nausea, severe headache with neck stiffness can be suggestive of meningitis. Acid reflux disease can also cause headache, nausea and abdominal discomfort.