Side-effect profile of modafinil is generally benign (e.g. headache, trouble sleeping, and nausea). Rare serious dermatological reactions may occur in people with genetic predispositions and more commonly in pediatric patients, and, discontinuation is recommended at the earliest signs of rash or similar reactions. Serious rare side effects may include allergic reactions such as anaphylaxis, Stevens–Johnson syndrome, and hallucinations in people with history of psychosis. It is unclear if use during pregnancy is safe. The amount of medication used may need to be adjusted in those with kidney or liver problems. It is not recommended in those with an arrhythmia, significant hypertension, or left ventricular hypertrophy. Modafinil appears to work by modulating the areas of the brain involved with the sleep cycle.