Myth: Organic and all-natural sunscreens are not as strong as the chemical based sunscreens.
Fact: The inherent ingredients in all natural sunscreens typically last longer in water than chemical ingredients.
Myth: SPF 100 provides the best protection, no need to use anything else.
Fact: SPF 15 protects you 93% against UVB rays. SPF 30 is 97%, SPF 50 is 98% and SPF 100 is about 99%. However, the higher the SPF factor the more chemicals you are exposing yourself to, for just one percent advantage.
Myth: Applying sunscreen 15 minutes before sun exposure and reapplying every two hours is necessary for best protection.
Fact: Some sunscreens last eight hours, but two hour reapplication makes up for best protection. Physical sunscreens start to work immediately; however, the chemical sunscreens need to be applied few minutes before sun exposure.
Myth: All sunscreens are the same.
Fact: There are different formulations available. You can find sunscreen for sensitive skin, sport, face, body or just lips. The facial sunscreen should feel light on the skin. Heavier formulation is great for the body.
Myth: There are no major differences between physical and chemical sunscreens.
Fact: Physical sunscreens use physical UV filters, while chemical sunscreens use chemical UV filters. There are also hybrid sunscreens that contain both physical and chemical sunscreen actives.
The differences between physical and chemical sunscreens are explained in the table below: 



Physical
How They WorkPhysical sunscreens protect your skin from the sun by deflecting or blocking the sun's rays.Chemical sunscreens work by absorbing the sun's rays. Some chemical filters can scatter sun rays, but still mostly just absorb them.
Other NamesSunblock; Inorganic sunscreenOrganic sunscreen
UV Filters
(UV filters are the active ingredient in sunscreens that protects you from the sun.) For more information about UV filters, their description, and other sunscreen active ingredients check here.
  • Titanium dioxide (TiO2)
  • Zinc oxide (ZnO)
  • Octylcrylene
  • Avobenzone
  • Octinoxate
  • Octisalate
  • Oxybenzone
  • Homosalate
  • Helioplex
  • 4-MBC
  • Mexoryl SX and XL
  • Tinosorb S and M
  • Uvinul T 150
  • Uvinul A Plus
StabilityGenerally stableMost are photostable, but some are not. Avobenzone is notoriously unstable. However, it can be stabilized when formulated in conjunction with other UV filters.
ComedogenicityTitanium dioxide can be problematic for some people. (If you break out from mineral make up and physical sunscreen, titanium dioxide could be the culprit.) Zinc oxide is generally safe. It can be used on delicate skin and is a main ingredient in diaper rash cream.Chemical filters tend to be more irritating to skin. If it gets in your eyes, it can make your eyes sting and water. Some can cause allergic reactions.
Protection
How much protection is offered depends on the amount of the active ingredient in the sunscreen, particle size of the UV filters, photostability, and overall product formulation.
Titanium dioxide protects against UVB rays, but not the full spectrum of UVA rays. Zinc oxide protects against the entire spectrum of UVB and UVA rays. Starts protecting immediately upon application.Chemical filters offer more coverage against UVA and UVB rays than physical sunscreens, but the range of protection will depend on the particular active and its stability. Avobenzone, for example, protects against the full spectrum UVA rays. Must wait 20 minutes after application for effective sun protection.
TextureThick and opaque, may be hard to apply. Tends to leave a white cast or tint. Rubs off more easily and must be frequently reapplied.Colorless, odorless, usually runny. Can sometimes double as a makeup primer, depending on the active and the formulation.
SafetyPretty safe, FDA approved. Don't cause free radicals. Note: Nanoparticle zinc oxide and titanium dioxide are controversial at the moment.Generally safe, however some chemical filters generate free radicals which can cause skin damage, irritation, and aging. Many chemical UV filters have not been FDA approved in the States, but are in sunscreens sold in Europe and Asia.




Hopefully this information will empower your decision making and lead to private after part-y's without tan lines or sun burn!