06 August 2008

The best sunblock varies from individual to individual. We recommend broad spectrum sunblock with UVA and UVB protection, a SPF rating of at least 30, in a form that is gentle enough for daily use.

Sunscreens come in two general types: chemical and physical.
  1. Chemical sunblocks penetrate the skin and absorb the sun's rays (UV radiation) before reach down into the lower layers of skin and cause damage then dissipating it as heat.
  2. Physical sunblocks lay a thin membrane on top of the skin that reflecst or scatter sunray’s (UV radiation) before it reaches the skin. It is often slightly coloured, such as zinc oxide and titanium dioxide which is white. They are not absorbed into the skin, thus they last longer and are needed to be applied on the skin just once which is enough for the whole day.
Some sunblocks combine both chemical and physical sunblocks.

Physical Sunblocks
The two types of physical sunblocks that are available are zinc oxide and titanium dioxide. Both provide broad spectrum UVA and UVB protection and are gentle enough for everyday use. It needs to be apply at least every three to four hours, like in the morning, noon, early afternoon, and late afternoon. Because these are physical blocking agents and not chemicals, they are especially useful for individuals with sensitive skin, as they rarely cause skin irritation.

Chemical Sunblocks
Most chemical sunblocks are composed of several active ingredients. This is because no single chemical ingredient blocks the entire UV spectrum (unlike physical sunblocks). Instead, most chemicals only block a narrow region of the UV spectrum. Therefore, by combining several chemicals,with each one blocking a different region of UV light, one can produce a sunblock that provides broad spectrum protection. The majority of chemical agents used in sunblock work in the UVB region. Only a few chemicals block the UVA region. Since UVA can also cause long-term skin injury, dermatologists at UCSF routinely recommends sunblocks that contain either a physical blocking agent (e.g. titanium dioxide or zinc oxide) or Avobenzone (also known as Parsol 1789).

Sunblocks Form
Sunblocks comes in a variety of forms. Lotions, oils, sticks, gels, sprays and creams can all be effective sunscreens. However, sunblocks are only effective if they are used. We encourage you to try several types and find the one which works and feels the best to you. All sunscreens should be applied 15-20 minutes before sun exposure to allow a protective film to develop, then reapplied after water contact and sweating. Some sunblocks can lose effectiveness after two hours, so reapply frequently.
Sunblock ProductSunblock Product

In general, spray lotions and gels are the least oily but also the ones that wash off more easily and need to be reapplied more frequently. If you develop a rash or other type of allergic response to a sunscreen, try a different brand or form (lotion vs. oil, for example) to see if you can better tolerate it. The most common allergic reactions occur with sunscreens that contain PABA-based chemicals. If you develop a rash to a sunblock, check the label to see if PABA is an ingredient. If so, consider avoiding sunblocks that contains this in the future. Alternatively, try a titanium dioxide or zinc oxide containing sunblock as they rarely cause skin irritation and provide very good broad spectrum UV protection.

Waterproof vs Water Resistant
Water resistant sunblocks are available for active individuals or those involved in water sports. It's important to check the label to ensure they say "water-resistant" or "waterproof (very water-resistant)".
  • Water Resistant sunblock maintains the SPF level after 40 minutes of water immersion.
  • Waterproof sunblock maintains the SPF level after 80 minutes of water immersion.
These figures only apply if you let yourself air-dry and don't use a towel. It is therefore always a good idea to rub on a layer of cream after going for a dip.

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