What Causes a Hangover Headache
The hangover headache is multi-factorial. Dehydration causes the brain to slightly reduce in volume, pulling on the membranes that connect it to the skull — this is a genuine mechanism for headache. Acetaldehyde causes blood vessel dilation, which is a direct headache trigger. Inflammation from alcohol metabolism releases cytokines that sensitise pain receptors. Sleep deprivation independently lowers pain thresholds.
The "just drink water" advice addresses one component (dehydration) but not the others.
What Actually Works
Prevention (most effective)
DHM before bed addresses acetaldehyde — the main headache driver. B vitamins support the metabolic processes that clear it. Hydration before sleep addresses dehydration. This three-part approach reduces headache severity the next morning more effectively than any morning remedy.
Morning relief
Paracetamol (acetaminophen) is effective for hangover headaches. Avoid ibuprofen on an empty stomach (gastric irritation) and aspirin (mixed poorly with residual alcohol). Caffeine helps by constricting blood vessels but dehydrates further — net effect is mild and temporary.
Hydration Timing
Rehydration before bed is significantly more effective than rehydration in the morning. When you sleep dehydrated, the dehydration has 7-8 hours to worsen — your body continues losing fluid through breathing and sweating even while asleep. A large glass of water before bed means you wake up less dehydrated.
The Pain Medication Caution
Paracetamol is processed by the liver. After heavy drinking, the liver is already working overtime. For moderate drinking, paracetamol at standard doses is considered safe. For heavy drinking, consider whether pain relief is necessary or whether hydration, food and time will manage it without adding to the liver's load.