How often do I need to reapply sunscreen?

How often do I need to reapply sunscreen?

Answer:

“Reapply sunscreen at least every 2 hours and” (immediately) “after swimming, sweating, or toweling off.”

Source: CDC.gov

https://www.cdc.gov/cancer/features/skin-cancer.html#:~:text=More%20sun%20safety%20tips,%2C%20sweating%2C%20or%20toweling%20off.

Opinion from Skyler, a Ginger who burns easily: 

“Reapply every 1 hour when you’re in direct sunlight because more is more. 

Seek shade whenever available, cover ALL exposed skin and avoid the sun when the UV index is a 3 or higher, which is typically from 10am to 4pm.

What about if I’m inside and not in direct sunlight and NOT by a window, do I still need to apply every 2 hours?

Official Answer #1 of 2

If you’re using oxybenzone/chemical sunscreen/blood barrier breaking sunscreen, even if you’re inside and not in direct sunlight and not by a window, you still need to reapply every 2 hours, because a 2020 FDA Study done indoors without without UV/sun exposure (which speeds up the chemical breakdown of sunscreens) found that:

Within 2 hours oxybenzone absorbs into your bloodstream within 2 hours of applying it, homosalate takes 3 hours to absorb into the bloodstream without any sunlight/uv exposure. 

Direct Quote:

“after single application, most participants had maximum plasma concentrations that reached or exceeded the 0.5-ng/mL threshold, with 75% or more of participants reaching that threshold within:

2 hours for oxybenzone (100%, n = 24/24), 

3 hours for homosalate (86%, n = 31/36),”

Source: https://jamanetwork.com/journals/jama/fullarticle/2759002

This is the closest I found to timing of absorption, but this study is just measuring when the safety threshold of what was absorbed in people was exceed, not necessarily the effectiveness of sunscreen but according to MDanderson.org:

“Chemical sunscreens wear off more quickly and need to be reapplied every couple of hours.”

Source: https://www.mdanderson.org/cancerwise/is-mineral-sunscreen-better-than-chemical-sunscreen.h00-159540534.html#:~:text=Chemical%20sunscreen%20absorbs%20UV%20rays&text=They%20come%20in%20both%20cream,sprays%20than%20with%20cream%20sunscreens.

If you know more about this, I spent hours trying to find a source that could show me a study that showed when exactly each chemical/blood barrier breaking sunscreen ingredient was in the bloodstream and therefore not protecting your skin, if you know please message me here and I’ll update this document titled “how often do I need to reapply sunscreen?’

 

Answer #2 of 2:

If you’re using Zinc aka mineral sunscreen and

 “if you’re spending all day inside and you’re not near a window, there’s no need to reapply as frequently. You can reapply every four to six hours.”

Source: https://www.skincancer.org/blog/ask-the-expert-how-often-do-i-need-to-reapply-sunscreen-if-im-indoors-all-day/#:~:text=That%20said%2C%20if%20you're,it's%20important%20to%20have%20protection.

Opinion: If I’m in direct sun for more than 2 hours, I reapply every 1-2 hours. 

That’s my typical day: 1 application in the morning after I dry off from my shower and before I put my clothes on, I get my face, ears neck and arms with tint 1 of sunshield plus and I’m good all day, protected from UV, HEV blue light, moisturized and it even covers blemishes for me. 

-Skyler Brady,

SunShield+ Founder