Crying is triggered by three distinct systems in your body: a baseline maintenance system that keeps your eyes moist, a reflex system that responds to irritants like onion fumes or dust, and an emotional system driven by your brain’s threat and bonding circuits. What makes each type of crying happen, and what your body actually does when tears start flowing, is more complex than most people realize.
Three Types of Tears, Three Different Jobs
Your eyes produce tears constantly. Basal tears form a thin film over the surface of your eye every time you blink, keeping the cornea lubricated and nourished. You never notice them because they’re doing exactly what they’re supposed to do quietly in the background.
Reflex tears kick in when something irritates your eyes. These are more watery and dilute than other tears because their job is to flush out whatever shouldn’t be there. They also carry higher concentrations of antimicrobial compounds that help prevent infection from foreign particles.
Emotional tears are chemically distinct from both. They contain more protein, which makes them thicker and stickier. That’s why emotional tears tend to cling to your skin and roll slowly down your face rather than streaming quickly the way reflex tears do. Research has also found that the metabolic pathways active in emotional tears differ depending on whether you’re crying from happiness or sadness, suggesting your body’s chemistry shifts based on the emotion itself.
Why Onions Make You Cry
The classic reflex tear trigger has a surprisingly specific chemical chain behind it. When you cut an onion, you break open its cells and release an enzyme called lachrymatory-factor synthase into the air. That enzyme converts the onion’s natural amino acid compounds into sulfenic acid, which is unstable and quickly rearranges into a volatile gas called syn-propanethial-S-oxide. When that gas reaches your eyes, it irritates the tear glands and triggers a flood of reflex tears to wash it away. Scientists originally blamed a different enzyme for this reaction, but a Japanese research team identified lachrymatory-factor synthase as the true culprit.
The same reflex system responds to smoke, strong wind, bright light, dust, and chemical fumes. Anything that threatens the surface of your eye can activate it.
What Happens in Your Brain During Emotional Crying
Emotional crying starts deep in the brain. The amygdala processes intense emotions like sadness, fear, or overwhelming joy. When it registers something powerful enough, it sends signals through several connected brain structures. A region called the periaqueductal gray controls the facial muscles and voice changes you experience while crying, which is why your face scrunches and your voice cracks before the tears even arrive.
A network of brain areas that controls automatic body responses (heart rate, breathing, digestion) also activates during a crying episode, which explains why heavy crying can leave you feeling physically exhausted. Your heart rate changes, your breathing becomes irregular, and your whole autonomic nervous system shifts gears.
The vagus nerve, part of the parasympathetic nervous system, plays a central role in both tear production and emotional regulation. It’s the main communication line between your brain and your tear glands during an emotional episode. This is the same nerve involved in the “rest and digest” response, which is why a good cry often leaves you feeling calmer afterward.
Common Emotional Triggers
Grief, frustration, helplessness, and physical pain are the most reliable emotional triggers for tears. But crying isn’t limited to negative emotions. Relief, gratitude, awe, and intense happiness can all produce tears through the same neural pathways. What these states share is emotional intensity that crosses a threshold your brain can’t easily regulate through other means.
Empathy is another powerful trigger. Watching someone else suffer, hearing a moving piece of music, or reading a story that resonates with a personal experience can all activate the same emotional circuits. Your brain doesn’t always distinguish cleanly between your own pain and someone else’s.
Hormonal shifts also lower the threshold for crying. Fluctuations in estrogen and progesterone during menstrual cycles, pregnancy, or menopause can make emotional tears come more easily. Sleep deprivation and chronic stress have a similar effect by weakening your brain’s ability to regulate emotional responses.
How Often People Cry
A study of self-reports from more than 7,000 people across 37 countries found that women cry emotional tears 30 to 64 times per year, while men cry 5 to 17 times per year. That’s a wide range in both groups, and individual variation is enormous. Some people cry weekly, others go months without shedding a tear, and both patterns fall within the normal range.
The gender gap is partly hormonal and partly cultural. Testosterone appears to raise the crying threshold, while socialization in many cultures discourages men from crying openly. The gap narrows somewhat in countries with greater gender equality, suggesting that social norms play a meaningful role alongside biology.
Why Crying Can Make You Feel Better
Crying releases oxytocin and endorphins, the body’s natural painkillers. These chemicals help ease both physical and emotional pain, which is why many people report feeling a sense of relief after crying. Emotional tears also flush stress hormones and other metabolic byproducts out of your system, giving the body a chemical reset of sorts.
Not every crying episode feels cathartic, though. Crying in a situation where you feel judged, ashamed, or unable to resolve the underlying problem often leaves people feeling worse. The relief effect is strongest when crying happens in a supportive environment or when it leads to some form of resolution or comfort.
From an evolutionary perspective, crying likely developed as a social signal. Tears are visible, hard to fake convincingly, and communicate vulnerability in a way that words alone can’t. The leading hypothesis is that crying evolved to signal distress and encourage helping behavior from others. Tears blur your vision, making you physically less capable of defending yourself, which may function as an honest signal of need. This aligns with findings that people generally feel more empathetic and willing to help when they see someone crying.
When Crying Becomes Difficult
Some people find they can’t cry even when they want to. This can have physical or psychological roots. On the physical side, conditions like Sjögren’s syndrome, lupus, rheumatoid arthritis, thyroid disorders, and vitamin A deficiency all reduce tear production. Aging naturally decreases it as well.
Several common medications suppress tear production, including antihistamines, decongestants, antidepressants, blood pressure medications, and hormonal birth control. If you’ve noticed you stopped being able to cry after starting a new medication, the drug itself may be the reason.
On the psychological side, emotional numbness from depression, trauma, or prolonged stress can shut down the crying response. Some antidepressants, particularly SSRIs, are known for creating a state of emotional blunting where sadness, joy, and the tears that accompany them all become muted. This isn’t a sign that something is wrong with you emotionally. It’s a neurochemical effect that often resolves with dosage adjustments or medication changes.