Post-swimming headaches are common, and they usually trace back to one of a handful of fixable causes: tight goggles, chemical irritation, dehydration, breathing problems, or cold water exposure. The good news is that most swimming headaches respond well once you identify the trigger.
Tight Goggles and Nerve Compression
One of the most overlooked causes of swimming headaches is goggle pressure on the nerves above your eyes. A nerve runs along the brow ridge just above each eye socket, and a tight goggle strap can compress it directly. This produces pain that radiates across the forehead and sometimes into the scalp. In one documented case, a swimmer who tightened his strap to stop a goggle leak developed scalp tenderness along the entire path of the nerve within a week. His pain took three weeks to fully resolve after he stopped wearing the goggles.
Some people are more vulnerable to this than others. The nerve exits the skull through either a fully enclosed bony tunnel or a shallow notch. If yours passes through a notch (less than 100% bony coverage), the nerve is more exposed and easier to compress. You can’t change your anatomy, but you can change your gear. Switching to goggles with a softer rubber seal and wearing the strap looser often eliminates the problem entirely. A neurologist who suffered bitemporal headaches after one to two hours of swimming was able to keep training pain-free simply by switching to a better-fitting pair.
Chloramine Fumes in Indoor Pools
That sharp “pool smell” isn’t actually chlorine. It’s chloramines, chemical byproducts that form when chlorine reacts with sweat, urine, and body oils in the water. The most irritating form, trichloramine, is highly volatile and collects in the air just above the water surface, exactly where you breathe.
In a 2006 outbreak investigated by the CDC at an indoor pool in Nebraska, 24 people fell ill from toxic chloramine levels in the air. Headache was among the reported symptoms, alongside eye irritation, blurry vision, and respiratory problems. The pool’s chloramine concentration was measured at eight times the acceptable maximum, and its extremely low pH accelerated the formation of the most irritating compounds. Indoor pools with poor ventilation are the worst offenders because the fumes have nowhere to go.
If your headaches happen mainly at indoor pools, try swimming at a facility with better airflow or an outdoor pool. Pools that smell strongly of “chlorine” are typically the ones with the highest chloramine levels, not the cleanest ones.
Dehydration You Don’t Notice
Swimming masks one of the body’s main warning signals for fluid loss: visible sweat. You’re surrounded by water, so you don’t feel yourself sweating, but you absolutely are. When you become dehydrated, your brain tissue shrinks slightly and pulls away from the skull, tugging on the pain-sensitive nerves that line it. The result is a dull, aching headache that can start during or after your swim.
Drinking water before and during your session is the simplest fix. If you’re swimming for more than 30 to 45 minutes, keep a water bottle at the pool edge and take sips during rest intervals. The headache from dehydration typically eases within an hour or two of rehydrating, though it can linger longer if you were significantly behind on fluids.
Breathing Patterns and Carbon Dioxide Buildup
Swimming demands coordinated breathing in a way that running or cycling doesn’t. Your face is in the water for most of each stroke cycle, and many swimmers, especially newer ones, breathe too infrequently or too shallowly. This can cause carbon dioxide to accumulate in your bloodstream faster than you’re clearing it. Elevated CO2 is a direct trigger for headaches, along with feelings of fatigue and shortness of breath.
Swimmers who practice bilateral breathing (alternating sides every three strokes) sometimes hold their breath longer than they realize. If you’re getting headaches, try breathing every two strokes on one side for a few sessions and see if the pattern changes. The goal is steady, rhythmic exhaling underwater so you can take a full, quick inhale when you turn. Exhale continuously through your nose or mouth while your face is submerged rather than holding your breath and then trying to exhale and inhale in one rushed moment at the surface.
Cold Water Exposure
Cold water can trigger headaches through direct stimulation of pain receptors in the face and scalp. The pain tends to hit faster and feel more intense when a large area of skin is exposed to cold water quickly, such as diving in rather than easing in gradually. Open water swimmers are especially prone to this in cooler conditions.
In rare cases, cold water triggers something far more severe. One swimmer developed what she described as the worst headache of her life, “like a rocket,” after swimming just three laps in a cold pool. She was diagnosed with reversible cerebral vasoconstriction syndrome (RCVS), a condition where blood vessels in the brain temporarily spasm. Her headache flared again three days later after a cold bath. A sudden, explosive headache during or after swimming, especially in cold water, is not a normal exercise headache and warrants immediate medical attention.
Neck Strain From Stroke Mechanics
Freestyle and butterfly both demand repetitive neck movements that can strain the muscles and joints of the upper cervical spine. In freestyle, every breath requires a combined rotation, flexion, and side-bending of the neck. Over hundreds of stroke cycles, this can produce tension that refers pain upward into the back of the head and behind the eyes.
Poor technique makes this worse. Lifting your head too high to breathe, rather than rotating your whole body, forces your neck to do more work in a less natural range. If your headaches concentrate at the base of your skull or wrap from the back of your head forward, neck strain is a likely contributor. Focusing on full-body rotation during freestyle breathing, so your head turns as part of a single rolling motion, reduces the isolated load on your neck considerably.
Sinus Pressure From Diving and Flip Turns
Water entering your nasal passages during flip turns, dives, or underwater swimming can create pressure imbalances in your sinuses. Your sinuses are air-filled cavities that need to equalize with the surrounding pressure. When that ventilation gets blocked, even briefly, you feel pain in the forehead or cheek areas. Among divers studied for sinus barotrauma, about 73% reported forehead pain and 53% reported cheek pain, with symptoms appearing most often during descent rather than ascent.
Recreational swimmers don’t experience the same pressure extremes as divers, but flip turns and shallow dives can still push water into the sinuses and create mild barotrauma. A nose clip can help if you’re prone to this, and avoiding swimming when you’re congested makes a significant difference since swollen nasal tissues block the tiny passages that let your sinuses equalize.
Exertion Headaches
Sometimes the headache is simply from hard physical effort. Primary exertion headaches feel like a throbbing pain on both sides of the head and come on during or just after intense exercise. They’re more common in hot environments and at altitude, but swimming intervals or racing pace can trigger them too. These headaches typically last anywhere from five minutes to 48 hours and tend to affect people who push into high-intensity efforts without a proper warm-up.
Easing into your workout with a few minutes of easy swimming, staying hydrated, and avoiding sudden maximal efforts can reduce the frequency. If you only get headaches after your hardest sessions, exertion is likely the primary cause.