Sunscreen, Sunblock: What’s the Difference?

You know you have to protect yourself against the sun’s ultraviolet rays (UV). Too much sun can prematurely age your skin, or worse, lead to skin cancer. So what do you use – sunscreen or sunblock? The answer is you use sunscreen. The FDA requires that term for any skin product with an SPF (Sun Protection Factor) of 15 or above because that means the product will block 90% or more of the harmful rays of the sun.

But there are differences in sunscreen products that are made to reflect the sun and those made to block the sun. And depending on the sensitivity of your skin to the sun, the differences may be critical to providing you with protection against the sun.

Applying sunscreen.  Sunscreening Alison by JasonUnbound, on Flickr
Applying sunscreen. Sunscreening Alison by JasonUnbound, on Flickr | Source

Chemical and Physical Sunscreens

There are two types of sunscreens: chemical and physical. Both protect against UVA (ultraviolet A) and UVB (ultraviolet B), the type of radiation most responsible for skin cancer. Look for the term broad spectrum on the product as that will describe a sunscreen that blocks both types of UV rays.

A chemical sunscreen prevents sun damage by “screening” and filtering UV radiation to prevent it from reaching your skin. It absorbs sunlight, but also lets sunlight get absorbed into your skin. This is typically what people call “sunscreen.”

A physical sunscreen provides a barrier or blockage to the sun’s rays. The sunlight is either absorbed into its ingredients or reflects the light away from your body. The sun’s damaging rays don’t reach your skin at all. This mirror-like effect is possible because of the type of reflective chemicals used in the sunscreen. This is what people typically call “sunblock.”

Sunscreen and Sunblock Ingredients

Following are some of the typical active ingredients you will find in sunscreens:

  • Aminobezoic Acid
  • Benzophenone
  • Cinnamate
  • Dioxybenzone
  • Octisalate
  • Octinoxate
  • Octyl Salicylate
  • Oxybenzone
  • PABA
  • Trolamine Salicylate

Sunscreens that act as sun blocks will often have one or more of the following ingredients:

  • Iron Oxide
  • Titanium Dioxide
  • Zinc Oxide

How much of each chemical is in the formula determines the amount of the sun’s rays that will get through. A small amount lets in a large amount of UV light. The more chemical that’s used, the more UV light will be blocked, keeping it from reaching your skin.

Skin Reactions to Sunscreen

Some people can have allergic reactions when they use sunscreen. This can be caused by one of the chemical ingredients, with PABA being one of the most common causes. If a fragrance is used in the sunscreen, it can also cause an allergic reaction.

You will be able to recognize an allergic reaction when one of the following occurs:

  • You skin begins to swell
  • Your skin begins to immediately turn red. This is not from sunburn, which usually takes a longer period of time to show.
  • You skin starts to itch.

If you notice any of these reactions, immediately rub the sunscreen off and seek further medical advice.

Sunscreen and Sunblock Appearance on Your Skin

Sunscreens without the sun block chemicals tend to be less visible when you put them on your skin. They also tend to break down after long exposure to the sun, which is why you need to reapply them. For more on applying sunscreen, read Applying Sunscreen the Right Way.

Sunscreens with the blocking chemicals often appear white on the skin. This makes them unappealing to many people. They can also feel greasier than the other type of sunscreen and may take more effort to remove. Newer formulations attempt to make sunblock products that are less messy and less visible when applied.

Which to Use

The differences between sunscreen and sunblock does not make one better than the other. In fact, many products contain both types of ingredients.

As per the FDA, the most important item to consider when buying sunscreen is the SPF number. Dermatology and cancer groups recommend at least an SPF 15 or SPF 30.

But if you have sensitive skin, you may want to turn to a sunscreen that has more of the sun block ingredients in it.

Note: Amazon products chosen based on positive customer reviews and EWG (Environmental Working Group) recommendations.

The Difference Between Sunscreen and Sunblock


The 2 minute video, by a doctor, gives a quick summary of the difference between sunscreen and sunblock.

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