One can experience mental symptoms, physical symptoms, or both. Common mental symptoms include cognitive dysfunction, intense discomfort, irritability, anxiety, craving for relief, susceptibility to nervous system stresses (e.g. cold), depressed mood, and difficulty communicating, remembering words, reading and retaining information, concentrating, and socialising. Physical symptoms include severe fatigue, mild to severe headache, and flu-like and allergy-like symptoms, such as sneezing, itchy eyes, nasal irritation, and muscle pain. Affected individuals may also experience intense warmth.