How much hard liquor is safe for very small children?

Question

I live in a location where hard liquor (48%-52% alcohol by volume) is frequently given to small children as young as two years old. This is usually not in large quantities, although a recent story in the local newspaper did report the death of a three-year-old by alcohol poisoning for consuming about 100ml in a short period of time. (This would be without water, as shots, and possibly on an empty stomach, per the local custom.)

Everyone knows that too much alcohol has averse effects, but I'd like to quantify this a bit if possible. Assume a healthy two-year-old child who weighs about 25 pounds; how much hard liquor would be unhealthy and why?

I'm looking for an answer that isn't zero for the sake of being zero (unless there's a true reason that any amount at all is damaging). Kids often taste it off the end of a chopstick or something similar, so dosages of <1ml in an evening may be realistic in the common case, a couple of times per month.

In other cases, a child will be able to drink from the glass, and once at a wedding I've seen a three-year-old nephew-in-law drunk as a result. His dad is undoubtedly giving him too much, but too much by how much?

This is the closest related answer I found on this site. The research cited suggests that even a short period of time with high exposure is damaging (which is obvious), but not really the minimum dosage for damage. Several sources posit that a little alcohol each day is healthy, suggesting a threshold effect is in place. Does the threshold also exist for children with developing brains, given alcohol quantities proportional to body weight and likely a coefficient related to mental development stage?

This is the closest related question I found on a web search. The Question was "If the quantity is small, is it still a risk?"; the Answer immediately sidesteps the question, asserts that 60ml is a small quantity, and then concludes by explaining that 60ml is not a small quantity.

The correct answer may be that the truth is intractable, similar to this fine answer, but the situation here is different. I'm not seeing multiple conflicting studies; rather, I'm seeing very little research on this topic. My guesstimate, based on absolute air, is that it's somewhere in the vicinity of 5ml, but I'm hoping there's some real relevant research out there given how important the issue and how absolutely prevalent of a practice it is.

Edit for clarification: For the purposes of this Question, I'm only interested in direct health effects and long-term damage, and not second-order effects like increasing propensity for alcoholism.

I'm really trying to understand how much physical machinery a two-year-old child has when it comes to processing alcohol, such that a few hours later they'd be just fine in the same way an adult is just fine after drinking a small amount of liquor.

Do the necessary enzymes exist at all in small children? If so, how much liquor would the child be able to process? (If not, what happened to the ~10ml that the child in my example consumed? What sort of damage did it cause?)

Answer 1

As I argue in my answer to this question, there seems to be a threshold in terms of the amount of alcohol likely to cause hepatocellular necrosis based on the production of acetaldehyde. However, alcohol causes damage to other cells in the body such as in the brain and throat. Since your example is of hard liquor, there would be damage to the mouth and esophagus not present from consumption of more dilute solution. Although beyond the scope of your question, many people would consider changes like habituation to the effects and long-term tolerance, and even "developing an acquired taste" which could increase the propensity for alcoholism, to be harmful.

A study of two hospitalized toddlers found that their alcohol consumption was somewhat under 20 mL for the first one (who drank an acetaminophen elixir) and 2 to 7 mL for the second one (who drank mouthwash and collapsed). So it seems that toddlers are more sensitive to the depressant effect of alcohol than adults per kg of body weight, and that it is feasible for them to drink enough alcohol to suffer respiratory arrest.

There is a whole thread on reddit discussing your very question. None of the answers were satisfyingly quantitative, but people pointed out that some pediatric medications contain ethanol (which should make it possible to calculate a "sanctioned" dose), that people in France and other places have a history of giving a little alcohol to young children, that ethanol is a metabolite (rum flavoring) or additive (flavoring extracts) in some foods, that it forms spontaneously in sugar-containing foods like juice and that it can form naturally in the intestine. So any of these approaches should make it possible to estimate a "normal" exposure of toddlers to ethanol, if not a "safe" one.