Who do the guidelines apply to?

Moderation  guidelines are set for an average healthy adult and therefore do not apply to young people who have not reached physical maturity, people with conditions which may be affected by alcohol such as pregnant women  or those with untreated high blood pressure, or  those taking medications  that do not combine well with alcohol. Those with a history of addiction or mental illness should abstain or consult their doctor for advice.

Young people can't cope with alcohol physically or emotionally as well as adults. That's why there are no safe limits for this age group, and laws exist to restrict purchase and consumption of alcohol by young people