This is probably not a hangover, as it is too soon for what most people refer to as a hangover. It is more likely due to the direct effects of alcohol itself, or perhaps something else in the drink. As is often the way with the human body, there can be several factors interacting together (these include the drink, hydration, liver function, environmental conditions, food etc).
This information is taken from The National Headache Foundation in the US:
Alcohol, which is consumed in beverages such as liquor, wine and beer, is a chemical called ethanol. Ethanol may cause headaches by several means. First, it is a direct vasodilator; in some individuals vasodilation may cause a headache. Second, ethanol is a natural diuretic; this leads to excretion of salt, vitamins and minerals from the body through the kidneys. Excess consumption of ethanol may produce dehydration and chemical imbalances in the body. Except in “moonshine,” we consume ethanol in beverages that contain other chemicals. These chemicals are called congeners. Congeners impart the specific tastes and flavors that make each beverage unique. These congeners also have a variety of effects that can cause headaches.
So the three ways alcohol can cause a headache are:
- Direct vasodilation effect (dilates blood vessels)
- Diuretic effect
- The effect of other components on the drink
If your whisky was about 40% alcohol, 200ml would be about 8 units of ethanol, which is definitely enough to have an effect.
