Also little things like mixing drugs with cold medicine is supposedly dangerous except coffee is fine.
In: Biology
For every drug, there’s a difference between how much is required for some effect and how much is required to kill you. Some particularly common drugs have surprisingly low gaps between the two, most notably alcohol and acetaminophen (at least compared to other drugs, like ibuprofen.)
So it’s really just that alcohol has a smaller gap between those two than, say, caffeine.
Caffeine *can* be dangerous in high doses, just like alcohol or, for example, heroin.
The difference is that for caffeine, a dangerous dose is many times larger than an effective dose.
A measure of a drug’s dangerousness is the size of a typical user dose divided my the size of a dangerous dose. The larger the ratio, the more dangerous the drug. A ratio of one means the user dose and the dangerous dose are the same, and the drug is very dangerous indeed.
Coffee is fine because it is (at least for a healthy person) incredibly hard to almost impossible to actually overdose on caffeine just by drinking coffee. The body gets rid of it pretty fast and the amount of liquid it is dissolved in kind of puts a limit on how much you can consume and makes you pee most of it out again. Pure caffeine is not safer than any other drug though. it is very much possible to die from a caffeine overdose, if you eat it pure.
As others here have noted, caffeine requires just a little bit of drug to work, vs. a lot to kill you. Caffeine will perk you up at 50-100 mg (the typical amount in a cup of tea or coffee) but won’t kill you until 10 grams, so the ratio of lethal/effective (aka the “therapeutic index”) is 100-200, i.e. “you’d need 100 times a regular dose to kill you.” For alcohol, that number is probably under 30. Alcohol also doesn’t have to kill you directly by shutting down brain function; at lower concentrations, it can cause nausea but also impair your ability to protect your airway, leading to vomit inhalation which is plenty deadly on its own. Then there’s impaired driving which can get lethal after just a few drinks.
I think OP is also hinting at why caffeine doesn’t seem to have some of the same risks in combination with other drugs. This comes down to what drugs actually do. Alcohol and other sedating drugs can have combined effects stronger than either drug alone, impairing consciousness and breathing. Sometimes they work in complementary ways that basically multiply their effect instead of simply adding up. Alcohol and benzodiazepines like Xanax or Valium are a good example; they work on the same target in different ways. Two drinks of alcohol have twice the effect of one drink, but one drink of alcohol plus one dose of a benzodiazepine can be much more than twice as strong (there’s not really math for this, it’s unpredictable in a dangerous way.)
Caffeine tends to have more stimulating effects so mixing it with alcohol won’t have combined sedation. That said, reducing the sedation of alcohol by adding caffeine may make it easier to drink unsafe amounts or do unwise things while drunk and energized, so it’s not risk-free.
If people could get fired for being on caffeine at work, civilization would literally collapse in a day. Just go with it, is what I’m saying.
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