It is recommended that as a general precaution all patients with a known history of chronic alcohol consumption encountered at emergency care are given thiamine 500 mg i.v. without delay. Alcohol crosses the blood brain barrier and will always cause CNS symptoms, which are most frequently attributable to ethanol. Treatment of alcohol withdrawal symptoms: see . A hangover is the mildest reaction to alcohol consumption. It is usually not associated with withdrawal seizures, unless the patient's seizure threshold is lowered by some other cause (scarring, tumour etc.). The cessation of chronic alcohol consumption results in withdrawal symptoms that are more severe than a hangover and may be accompanied by seizures or delirium tremens.