What’s the Difference Between a Sunburn and a Tan?

It starts innocently enough. Maybe you’re stretched out on a beach towel, cheering at a baseball game, or spending a little too long pulling weeds in the garden. Hours later, you catch your reflection in a mirror and realize your skin looks different. It might have turned toasty brown. It might be bright red. Sometimes, it’s a little of both depending where you look.

These summertime skin souvenirs are so common that most of us hardly think twice about them. A tan is often treated as a sign of time well spent, while a sunburn is a painful mistake to be avoided. But what exactly separates the two? Why does an afternoon in the sun sometimes leave us bronzed, but other times burned?

Turning Up the Tint

At first glance, a tan and a sunburn may seem like very different outcomes. But they’re actually closely related responses to the same thing: ultraviolet (UV) radiation from the sun.

When UV rays strike your skin, they can do serious damage to your DNA and other important cells and tissues in the body. To help protect you, your body ramps up production of a pigment called melanin, which gives your skin its color. Melanin acts like a natural shield, absorbing and dispersing some of the incoming UV radiation before it can wreak more havoc.

As melanin first builds up during your gardening session or at the ballgame, your skin darkens. This is what gives you a tan. But melanin can only do so much. If the amount of incoming UV radiation exceeds your skin’s ability to protect itself, damage begins to accumulate. That’s when a sunburn occurs.

And sunburns do more than just ruin your vacation photos. They’re actually an inflammatory response — your damaged skin cells are releasing distress signals that trigger increased blood flow to the now lobster-like area. This defense mechanism causes the redness, warmth, and pain that may have you reaching for the aloe vera. A severe sunburn is also colloquially referred to as sun poisoning. You’re not being poisoned, but your body’s response is strong enough to cause nausea, chills, fever, and other intense symptoms.

The time it takes to tan versus burn depends on a variety of factors, including how long you’ve been basking in the sun, how intense the UV is that day, and your genetics (pale skin will burn much faster than darker skin). Because UV light, which isn’t visible, passes through clouds, you can even tan or burn on an overcast day.

It’s worth noting that a tan doesn’t mean you’ve escaped any sun-related harm. Dermatologists consider a tan to be evidence that UV exposure has already caused skin damage and raises your risk of skin cancer (sorry). That means, unfortunately, that there’s really no such thing as a “healthy” tan.

Sunscreen can help block some UV particles and reduce skin damage, but at the end of the day (when the sun has set), it’s your skin that has been hard at work keeping you healthy. (Covering up with a hat and long sleeves while outdoors, of course, makes the job a lot easier.) But whether you leave the sun with a golden glow or a painful burn, both are reminders that you can have too much of a good thing — especially when it comes to sunlight.