 Alcohol hangover symptoms develop when blood alcohol concentration falls considerably and peak when it returns to almost zero.Hangover symptoms validated in controlled studies include general malaise, thirst, headache, feeling dizzy or faint, tiredness, loss of appetite, nausea, stomach ache, and feeling as though one's heart is racing.Some symptoms such as changes in sleep pattern and gastrointestinal distress are attributed to direct effects of the alcohol intoxication, or withdrawal symptoms.