The people who have trouble drinking (like me) have enzymes in their liver

to change the ethyl alcohol to acetaldehyde rapidly as a detoxification defense

This is what's causing the palpitation, flushed face, headache, and other unpleasant reactions.

This acetaldehyde is oncogenic. After drinking, their blood contains acetaldehyde

and not much alcohol. That's why they don't get euphoric. These people are mostly Asians.

People who enjoy drinking have much fewer enzymes to convert alcohol to acetaldehyde.

They get a lot of pure alcohol in the blood that is euphoric and is not much oncogenic.

So, the damage and cancer happen more often in people who don't enjoy drinking.

So, people who do not enjoy drinking should not drink at all

while people who enjoy drinking may drink without worrying about cancer.

But they will have to worry about alcoholic dementia and cardiac arrhythmia.

I may be wrong but this is how I understand about drinking.

There is a strong scientific consensus that alcohol drinking can cause several types of cancer (1, 2). In its Report on Carcinogens, the National Toxicology Program of the US Department of Health and Human Services lists consumption of alcoholic beverages as a known human carcinogen.

The evidence indicates that the more alcohol a person drinks—particularly the more alcohol a person drinks regularly over time—the higher his or her risk of developing alcohol-associated cancer. Even those who have no more than one drink per day and binge drinkers (those who consume 4 or more drinks for women and 5 or more drinks for men in one sitting) have a modestly increased risk of some cancers (3–7). Based on data from 2009, an estimated 3.5% of cancer deaths in the United States (about 19,500 deaths) were alcohol-related (8).

Clear patterns have emerged between alcohol consumption and the development of the following types of cancer:(refer to the text)

Can people's genes affect their risk of alcohol-related cancers?

A person’s risk of alcohol-related cancers is influenced by their genes, specifically the genes that encode enzymes involved in metabolizing (breaking down) alcohol.

For example, one way the body metabolizes alcohol is through the activity of an enzyme called alcohol dehydrogenase, or ADH, which converts ethanol into the carcinogenic metabolite acetaldehyde, mainly in the liver. Recent evidence suggests that acetaldehyde production also occurs in the oral cavity and may be influenced by factors such as the oral microbiome.

Many individuals of East Asian descent carry a version of the gene for ADH that codes for a "superactive" form of the enzyme. This superactive ADH enzyme speeds the conversion of alcohol (ethanol) to toxic acetaldehyde. Among people of Japanese descent, those who have this form of ADH have a higher risk of pancreatic cancer than those with the more common form of ADH.

Another enzyme, called aldehyde dehydrogenase 2 (ALDH2), metabolizes toxic acetaldehyde to non-toxic substances. Some people, particularly those of East Asian descent, carry a variant of the gene for ALDH2 that encodes a defective form of the enzyme. In people who produce the defective enzyme, acetaldehyde builds up when they drink alcohol. The accumulation of acetaldehyde has such unpleasant effects (including facial flushing and heart palpitations) that most people who have inherited the ALDH2 variant are unable to consume large amounts of alcohol and therefore have a low risk of developing alcohol-related cancers. 

However, some individuals with the defective form of ALDH2 can become tolerant to the unpleasant effects of acetaldehyde and consume large amounts of alcohol. Epidemiologic studies have shown that such individuals have a higher risk of alcohol-related esophageal cancer, as well as of head and neck cancers than individuals with the fully active enzyme who drink comparable amounts of alcohol (31). These increased risks are seen only among people who carry the ALDH2 variant and drink alcohol—they are not observed in people who carry the variant but do not drink alcohol(refer to the text)

https://www.p65warnings.ca.gov/products/alcoholic-beverages

New Warning (effective 8/30/16)

The moral of the stories in the above comments are:

1. If you get red-flush, palpitation, feeling bad, and other alcoholic reactions

without getting euphoric, you are the people with abundant ADH and ALDH2 and thus,

get exposed to a large amount of acetaldehyde when you drink. That means you should not drink.

2. The drinkers should never offer drinks to the person who is one of the people in the above phrase.

Drinkers are giving cancer and killing their friends under the name of stupid friendship

and macho-man-ship.

In so many times, drinkers force the glass on their non-drinking friends. Such behaviors should stop.

3. Non-drinkers should not join the drinking occasion. By all means, avoid joining the drinking table.

If someone tries to force you to drink, just get up and get out. You do not need such an idiotic friend.

4. Non-drinkers should not try to show macho-sprit as he is killing himself.

Nothing is more stupider than this bravado and camaraderie.