The quick answer is no, sunscreen doesn’t block infrared light, and you don’t need to block it.
The wavelengths of UV coming from the sun are classified as UV-A (320–400 nm), UV-B (290–320 nm), and UV-C (100–290 nm). UV-C has the highest energy, making it the most dangerous of the three-wavelength types. Luckily, the earth’s ozone layer protects UV-C (light that is even higher energy than UV is absorbed by nitrogen in the atmosphere), leaving UV-A and UV-B wavelengths to be of concern. The high energy of photons of UV light can penetrate the skin and trigger damaging reactions within the skin’s DNA or excite other chromophores present in the skin to form reactive oxygen species (ROS).
Ninety-five percent of UV radiation that reaches the earth’s surface is UV-A radiation. UV-A radiation triggers the tanning reactions in the skin, as the skin darkens in an attempt to protect itself from further damage. UV-A plays a major role in skin aging. It also causes damage to the epidermis (the outermost layer of the skin) and is a factor in developing skin cancers.
Types of UV
Wavelength: 320–400 nm.
Effects: Tanning, Premature skin aging, Skin cancer.
Protection: Avobenzone (Parsol 1789), Ecamsul (Mexoryl), Zinc oxide.
Wavelength: 290–320 nm.
Effects: Vitamin D production, Sunburn, Cataracts, Genetic damage, Skin cancer.
Protection: Oxybenzone, Homosalate, Octinoxate, Octisalate, Titanium dioxide.
Wavelength: 100–290 nm
Effects: Cellular decomposition
Protection: Ozone in the lower stratosphere
A sunscreen product’s efficacy is commonly indicated by its “sun protection factor” or SPF. The SPF indicates how long it will take for UV-B rays to begin to redden the skin. Skin coated with an SPF 15 sunscreen will take 15 times longer to redden than without the sunscreen.
Infrared waves, or infrared light, are part of the electromagnetic spectrum. People encounter Infrared waves every day; the human eye cannot see them, but humans can detect them as heat. The remote control uses light waves beyond the visible spectrum of light — infrared light waves — to change channels on your TV.
Do I Need to Protect Myself?
Sunscreens do not shield skin from any infrared rays. Topical antioxidants should help shield the skin. Ignore the chatter about infrared. Ignore the sunscreens which claim to block infrared.
Focus on protecting your skin from UVA and UVB using a broad-spectrum sunscreen and physically keeping the sun off your skin with clothing, a hat, and shade. Yes, wear UPF 50 clothing and a sun hat when outdoors. Head for the shade or create it. Apply mineral zinc oxide-based sunscreen to exposed skin not covered by UV-blocking clothing. There is no controversy with these recommendations, and your skin will look great and stay strong for your lifetime if you protect it from UV exposure.
Daniel Barolet, François Christiaens, and Michael R Hamblin, Infrared and Skin: Friend or Foe, J Photochem Photobiol B. J Photochem Photobiol B. 2016 Feb; 155: 78–85.
Laura Hudson Eyman Rashdan Catherine A. Bonn Bhaven Chavan David Rawlings Mark A. Birch‐Machin, Individual and combined effects of the infrared, visible, and ultraviolet light components of solar radiation on damage biomarkers in human skin cells, The FASEB Journal, Volume34, Issue3, March 2020, 3874–3883 https://doi.org/10.1096/fj.201902351RR