What could cause rapid heart beat and flushing after drinking alcohol?

Intoxication: Alcohol causes many health problems such as dehydration that can cause a rapid heart rate. There also is a condition known as the holiday heart syndrome that happens the day after a heavy night of drinking this is usually a sign of mild withdrawels, if these are happening to you see a doctor anyway to do an ekg and other tests to make sure its not more serous.

Rapid heart beat: Alcohol is a vasodilator, you can see some flushing following which you can have tachycardia. Excitement also makes heart rate to go up.

Genetic variant: Some people have a genetic variant of an enzyme that metabolizes alcohol. The aldh2 gene regulates the production of the enzyme aldehyde dehydrogenase 2 that transforms acetaldehyde into acetic acid. The aldh2*2 variant is common in individuals of east asian descent (45-50%), but is extremely rare in most non-asian populations. When drinking alcohol, these people flush, have tachycardia, etc, .