Wonder: How does sunscreen work?

By: Maddie Jewell

Find it Out!

Every time I put sunscreen on, I think to myself, “How in the world does this thin, clear layer of lotion actually protect me from harmful rays?” So, I decided to do a bit of research.

Sunscreen is made by combining organic and inorganic ingredients. Wait. What in the world does that mean? Basically, an organic compound is one that contains carbon while inorganic compounds do not. These ingredients are the skin protectors – they’re what keep the harmful ultraviolet radiation from harming the skin. Alright, but what exactly is “ultraviolet radiation?” Well, ultraviolet radiation, also known as UV radiation, is the type of radiation that comes from the sun. There are three different types of this UV radiation that include the following:

  • UV-A: This radiation can really do some damage! It has longest wavelength, and it’s so strong that even the ozone layer can’t absorb it. Even though these aren’t directly responsible for sunburn, they can have harmful effects like skin cancer.
  • UV-B: Ouch. This radiation causes sunburn. Even though it is partially blocked by the ozone layer, it still can cause intense sunburn and painful blisters on skin.
  • UV-C: Don’t worry about this radiation! It is completely absorbed by the Earth’s atmosphere. The only time this is ever experienced is when artificial radiation is created.

Okay, so now that we’ve covered the basics of UV radiation, what actually makes up these organic and inorganic ingredients, and what do those ingredients do? Sunscreen usually consists of the inorganic ingredients zinc oxide or titanium oxide. These reflect and scatter the UV radiation so that it doesn’t come in contact with your skin. Unfortunately, though, these inorganic compounds aren’t always enough. The organic ingredients like octyl methoxycinnamate (OMC) or oxybenzone absorb whatever radiation slips through the inorganic ingredient cracks and disperse that radiation as heat.


So what exactly should you be looking out for when you’re on the way to the beach and need to run into the store and grab some sunscreen? Well, the Sun Protection Factor, also known as SPF (who knew that’s what SPF stood for?!), measures how effectively whatever ingredients make up that bottle limit UV-B exposure. Remember, those are the ones that burn your skin! However, normal sunscreen doesn’t protect against harmful UV-A rays. If you want to be extra careful, look for bottles that say “broad-spectrum” on the labels. This way, you will be protected from all the bad UV radiation!

Try it Out!

Want to experiment and find out which sunscreen brands and SPF levels work best? Try these experiments and learn!

  • Use a pack of Sun Sensitive Paper or UV beads, sunscreen, and sunlight to figure out how much protection your sunscreen gives you! Follow these instructions!
  • Not believe in sunscreen? Test it out with some construction paper and sunscreen! If you want, you can even modify this experiment and test different types of sunscreen on the same sheet of paper to see which one works best!