Why Do We Cry Emotional Tears Differently Than Onion Tears
Key takeaways
- Tears come in three types: basal tears for daily lubrication, reflex tears that flush irritants, and emotional tears triggered by strong feelings.
- Emotional tears contain more protein-based hormones, including prolactin, ACTH and leucine enkephalin, than basal or reflex tears do.
- Onion tears are reflex tears: the gas syn-propanethial-S-oxide irritates the eye, and the lacrimal gland responds with a watery flush.
Your eyes produce three distinct kinds of tears, and they are not interchangeable. Basal tears quietly coat the eye all day, reflex tears flood it in an emergency, and emotional tears arrive when grief, joy or frustration takes over.
Chemically, they differ more than you might guess. Reflex tears, the kind onions provoke, are mostly water with salt. Emotional tears carry a richer mix of protein-based hormones, including prolactin, adrenocorticotropic hormone (ACTH) and leucine enkephalin, a natural painkiller, according to Wikipedia's overview of tear research.
This article takes a closer look at the three types of tears, including how onions trigger reflex tears, what makes emotional tears chemically different, and what crying does for the rest of your body.
What are the three types of tears?
Basal tears are the background crew. They keep the cornea wet and nourished around the clock, and the eye secretes roughly 0.75 to 1.1 grams of tears in a 24-hour period, with the rate slowing as people age, Wikipedia reports.
The tear film itself has three layers. A mucous layer anchors the tear to the eye, a middle watery layer hydrates and protects the cornea, and an oily outer layer slows evaporation and keeps vision sharp. Blinking spreads this film across the eye, and quality of vision depends on it staying stable.
Reflex tears are the emergency response. They appear when the eye meets irritants like smoke, dust, pepper spray, perfume or onion fumes. Irritation can raise tear secretion roughly 100-fold, up to about 300 microliters per minute, compared with a basal rate of roughly 0.5 to 2.2 microliters per minute.
Emotional tears are the odd ones out. They follow strong emotional stress, pleasure, anger, grief or physical pain, and people also cry when extremely happy or laughing hard. Wikipedia notes that emotional tears differ in chemical makeup from lubrication tears, carrying more of the hormones prolactin, ACTH and Leu-enkephalin than basal or reflex tears.
The wiring behind each type is different, too. The trigeminal nerve (cranial nerve V1) carries the sensory pathway of the tear reflex. If that nerve is cut, reflex tears stop while emotional tears continue, which shows the two responses travel through separate circuits.
How onions trigger reflex tears
Cutting an onion breaks open its cells and sets off a small chemical chain reaction. Sulfur from the soil where the onion grew mixes with the onion to create amino sulfides, and chopping releases enzymes that convert these into sulfenic acid, Healthline explains.
The sulfenic acid then rearranges into a volatile gas called syn-propanethial-S-oxide. This gas drifts upward, contacts the eye, and irritates it. The lacrimal glands, located above the eyes, answer with a flood of reflex tears designed to wash the irritant away.
That is the entire trick. Your eyes treat onion gas like any other intruder, and the response is a protective flush, not an emotional event. Other airborne triggers do the same job, including strong perfumes, chlorine, dust and even bright lights, which is why a bright flash can make some people water up in a way that resembles sneezing at bright light.
What makes emotional tears chemically different
In the early 1980s, biochemist Dr. William Frey at the Ramsey Medical Center in Minnesota began collecting and comparing emotional tears with reflex tears. He found that emotional tears contain higher levels of stress-related hormones and proteins than the watery reflex kind.
The three molecules most often named are prolactin, ACTH and leucine enkephalin. ACTH is released during stress.
Leucine enkephalin is an endorphin-like compound involved in pain regulation. Prolactin is best known for its role in milk production, and women carry about 60 percent more of it than men, according to Healthline.
Researchers at the Center for Academic Research and Training in Anthropogeny (CARTA) describe emotional tears as richer in proteins, especially hormones, as well as potassium and manganese, compared with basal and reflex tears. They add that the bulk of emotional tears appear to come from the lacrimal glands, which in humans are more richly connected to brain areas involved in deep emotion than in other primates.
Frey suggested that emotional crying might help the body excrete stress-related chemicals that build up during distress. "Crying is not only a human response to sorrow and frustration, it's also a healthy one," he said, calling it a natural way to reduce emotional stress.
That idea is worth keeping in perspective. The hormone findings are widely cited, but the exact concentrations and their health effects remain debated, and modern researchers continue to study what emotional tears do beyond signaling. Healthline notes that the purpose of emotional tears is still being researched, with biological, social and psychological factors all in play.
Why your nose runs when you cry
Emotional crying often comes in volume, and that volume overwhelms the eye's drainage plumbing. Tears normally drain through tiny holes in the corners of the eyelids, called puncta, then travel down small channels and tear ducts into the nose.
A hard cry produces more fluid than the nasolacrimal ducts can carry away. The excess mixes with mucus in the nasal passages, which is why your nose runs when you cry and often keeps running in cold air for a similar drainage reason.
CARTA points out that emotional tears differ from other tear types in volume, streaming visibly onto the face precisely because they overwhelm the normal drainage pathway. The salt in tears, mostly sodium, is also why a tear that reaches your lip tastes the way it does.
Newborns, interestingly, cry without tears at all for the first month or so, because their lacrimal glands are not fully developed yet, Healthline reports.
What does crying do for the body?
Crying touches more than the eyes. Breathing and heart rate typically slow after a bout of crying, and the body shifts toward a calmer state, driven by the parasympathetic branch of the autonomic nervous system. This is the same branch that controls the lacrimal glands through the neurotransmitter acetylcholine, per Wikipedia.
There is also a social layer. Humans appear to be unique among primates in producing emotional tears, according to CARTA, and researchers treat the visible tear as an honest signal of emotional state that evolved alongside human cooperation and bonding. Other people read a crying face as a request for help, and they usually offer comfort, which is part of why crying can leave people feeling better.
Emotional tears may even send chemical signals. A 2011 study found that men who sniffed women's emotional tears, collected during a sad movie, rated female faces as less sexually attractive and showed lower sexual excitement, confirmed by saliva tests and MRI scans, Healthline reports. Tears are odorless, yet they carry messages others can sense.
Physical reactions to emotion run through the whole body. The shiver down your spine in a tense moment is another example of the nervous system answering a feeling, similar to getting goosebumps when you are cold or scared.
Are onion tears and emotional tears really different substances?
Yes, in composition. Reflex tears are mostly water, salt and protective proteins. Emotional tears carry extra protein-based hormones such as prolactin, ACTH and leucine enkephalin.
Does crying flush toxins out of the body?
This is the most repeated claim about crying, and it deserves caution. Frey's work suggested emotional tears excrete stress-related hormones, but the exact quantities and their health impact are debated. What is better supported is that crying calms the nervous system and signals others to help.
Do men and women cry differently?
Women tend to cry more often, and one physiological thread is prolactin. Women have roughly 60 percent more prolactin than men, and emotional tears contain this hormone. Cultural norms likely shape the gap as well.
Can you run out of tears?
No. Tear production can slow with age, illness or hormonal changes, which is why dry eyes become more common in older adults, especially women after menopause. The glands keep working, just less generously.
Outlook
The difference between a grief tear and an onion tear is chemistry plus wiring. One starts in the brain's emotional circuits and arrives loaded with hormones. The other starts at the eye's surface and arrives as a watery flush.
Research is still filling in the details of what emotional tears do for the body. The hormone differences Frey documented in the 1980s remain the best-known finding, while newer work on tear biomarkers is exploring what tears can reveal about health more broadly.
It is a good idea to see an eye doctor if your eyes water constantly without an obvious trigger, since overflow tearing can signal blocked ducts or dry eye rather than emotion.
This article is for general information, not medical advice.
Tags: tears, emotional tears, reflex tears, onion tears, eye health
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