National Smile Day - May 31, 2027

National Smile Day is celebrated annually on May 31, and few occasions make a stronger case for themselves simply by existing. A smile is one of the body's most efficient tools: it shifts mood, signals trust, and crosses every language barrier without effort. Science has spent decades confirming what most people already sense intuitively, that smiling regularly produces measurable benefits for both physical health and social connection.

National Smile Day History

The smile as a social signal predates human civilization entirely, with primatologist Signe Preuschoft tracing its origins to the teeth-baring behavior of monkeys and apes, who used the expression to establish dominance or signal threat rather than pleasure. Over thousands of years of human evolution, that same gesture was gradually repurposed to convey warmth, attraction, and shared amusement, becoming one of the few truly universal forms of nonverbal communication. Research into early human behavior suggests the smile played a role in mate selection long before it became the social lubricant it is today.

For centuries, smiling in formal portraits was considered a sign of poor breeding, linked to the aristocratic belief that visible emotion indicated a lack of self-control. Widespread tooth decay from sugar-heavy diets also made open-mouthed expressions something most people actively avoided, with Leonardo da Vinci's Mona Lisa being one of the rare and famously ambiguous exceptions. National Smile Day was founded by dentists Dr. Tim Stirneman and Jim Wojdyla of Compassionate Dental Care in Lake in the Hills, Illinois, to reclaim the smile as something worth nurturing and showing off rather than hiding. French neurologist Guillaume Duchenne contributed to that understanding by identifying two distinct types of smiles: the genuine kind, which engages the muscles around the eyes, and the polite or performative kind, which does not.

Photographic evidence has helped researchers track how smiling norms have evolved over time, with studies of yearbook photos showing that the width and frequency of smiles in images increased significantly across the 20th century. Part of that shift is technical: early photography required subjects to hold expressions for long periods, causing genuine smiles to fade into neutral looks. Cultural factors also play a significant role, with research finding that countries with long histories of diverse immigration, like Brazil and the United States, show higher rates of smiling because the expression functions as a shared language when spoken ones diverge.

Why National Smile Day Matters

Dental Health Is Part of the Picture

A smile people feel good about starts with teeth they're not self-conscious about, which is why this occasion places real emphasis on dental care alongside the social and emotional dimensions. Regular checkups, proper hygiene, and early treatment of problems all contribute to the kind of confidence that makes smiling feel natural rather than forced.

It Changes How Others See You

People consistently rate those who smile as more competent, approachable, and trustworthy in first impressions, which has measurable effects in professional and social settings alike. A smile signals openness in a way that body language and clothing rarely can, creating a momentary connection that tends to outlast the interaction itself. Workplaces where smiling is common also report higher levels of creativity and collaboration among teams.

It Works on the Body

Smiling triggers a real physiological response, reducing cortisol levels, lowering blood pressure, and releasing endorphins that shift mood almost immediately. The effect holds even for smiles that aren't entirely genuine, which means the act itself carries benefits independent of whether the feeling came first. Over time, regular smiling has been linked to stronger immune function and greater physical endurance.

How To Celebrate National Smile Day

Book a Dental Appointment

Given that this day was created by dental professionals, using it as a prompt to schedule a checkup is both on-theme and genuinely useful. Many people put off routine visits until something hurts, which is usually the more expensive and uncomfortable outcome. Treating May 31 as an annual reminder keeps the habit consistent and gives the smile itself a stronger foundation.

Do Something That Makes Someone Laugh

Go beyond your own smile and take deliberate action to produce one in someone else, whether that's a well-timed joke, an unexpected small kindness, or showing up somewhere you know your presence will be a surprise. The effort required to make another person genuinely smile tends to lift your own mood in the process. That reciprocal quality is what makes smiling one of the more efficient investments in daily wellbeing.

Smile at a Stranger Today

The simplest possible way to mark this occasion is also the one with the most immediate feedback: make eye contact with someone you don't know and let a genuine smile follow. It costs nothing and tends to produce an involuntary response in the other person, which is exactly the kind of small, compounding effect this day is built around. Do it more than once and notice how it shifts the overall tone of your day.

Facts About Smiling

Babies Smile Before Birth

Ultrasound imaging has captured fetuses forming smile-like expressions in the womb, suggesting the expression is hardwired rather than learned through social imitation.

Smiling Is Faster Than Frowning

The muscles required to produce a smile are fewer in number than those used to frown, making it the physically easier expression of the two despite the popular myth claiming the opposite.

Fake Smiles Use Different Muscles

Genuine smiles engage the orbicularis oculi muscle around the eye, while polite or performed smiles typically activate only the muscles around the mouth, a distinction detectable even in photographs.

Smiling Is Contagious by Design

Mirror neurons in the brain respond to observed facial expressions by triggering the impulse to replicate them, which is why smiling at someone almost always produces a smile in return.

Children Smile More Than Adults

Research suggests children smile up to 400 times per day on average, while most adults smile far less frequently, with habitual smilers typically reporting higher overall life satisfaction.

National Smile Day Dates