A commonly asked question from clients is the difference between a chemical-based SPF and a physical-based SPF and which one is right for you? Are you an athlete that sweats? Do you have reactive skin? Are you prone to redness or hormonal skin conditions such as melasma?
On a molecular level, physical and chemical SPF are very different.
Chemical sunscreen - Chemical sunscreens contain carbon-based ingredients: oxybenzone, avobenzone, oxtinoxate, and oxtisalate. They absorb one or both (depending on the formula) of UVA and UVB rays before turning them into heat and then releasing the heat from the skin.
Benefits / Negatives - Chemical SPF's are usually in thinner formulas, easier to apply depending on the formula, available in many stores so easy to obtain and are often less expensive. The downside to chemical SPF's are that they do not all protect against UVA (aging rays- the ones that cause wrinkles!), they can and are a common cause of skin reactions (so for sensitive skin they can be aggravating), they can sting when it gets in the eyes from sweating, you need to apply 15 mins before sun exposure, and sensitive skin, melasma and redness may be aggravated (possibly due to the heat conversion). Certain chemical SPF's are controversial and have been banned in Europe. Other chemical sunscreens can be harmful to the coral reefs (oxybenzone & oxtinoxate) and are banned in Hawaii.
Physical sunscreens - Physical sunscreens contain one or both of the mineral-based ingredients titanium dioxide & zinc oxide. These are the only 2 physical sunscreens. They reflect ultraviolet aging (UVA) rays away from the skin. Think of these minerals as little mirrors on your skin scattering and deflecting rays away from you.
Benefits / Negatives - The benefits of a physical SPF is that they offer natural broad spectrum protection (UVA and UVB ray coverage), there is often little to no irritation, in fact physical SPF can actually benefit sensitive skin and acne depending on the formula, and you can apply and immediately are protected from rays without any wait and they are reef safe if non-nano. The downside to physical SPF's is they can have a thicker feel, can leave a white shadow, and have to be applied generously. However, the newest formulas of physical SPF have come a long way and now are available in invisible, thinner, elegant formulas.
While we love physical sunscreens here at Skin Theory, we also really like formulas that contain both safe, healthy-for-you organic chemical sunscreens along with the Physical mineral SPF. We love Skin Theory ClearScreen Broad Spectrum SPF30 w/ Vitamin c and Face Reality invisible Ultimate daily SPF28 for acne prone skin, Tizo tinted and non-tinted SPF40 for hyper-pigmented, melasma and redness prone skin, SolRX50 acne-safe sport sunscreen. Super Goop Body Spray-on pure Mineral SPF go on sheer and beautiful.