~Sunblocks: What you need to know~

In order to prevent getting a sunburn while you are outdoors, you must apply a sunblock or sunscreen at least half an hour before sun exposure.

Majority of the people use the terms "sunblock" and "sunscreen" interchangeably but actually they are not the same.

Sunscreen absorbs ultraviolet rays so that it does not reach your skin while sunblock physically blocks the sun's UV rays.

Sunblocks

Sunblock usually contains titanium dioxide or zinc oxide.
Both provide broad spectrum UVA and UVB protection and are gentle enough for everyday use. Because these are physical blocking agents and not chemicals, they are especially useful for individuals with sensitive skin, as they rarely cause skin irritation.
Although they work well, they are usually opaque, meaning they form a visible white layer on your skin.

Sunscreens
Most sunscreens are composed of several active ingredients.
So a sunscreen that provides broad spectrum protection has a combination of several chemicals with each one blocking a different region of UV light.

The majority of chemical agents used in sunblock work in the UVB region. Only a few chemicals block the UVA region. Chemical agents that block UVA rays too are avobenzone, oxybenzone, and octocrylene.
I see avobenzone more often when I check out sunblocks on the market.

Common active ingredients of sunblock and the type of UV light blocked:

Active Ingredient	Type of UV radiation blocked
Aminobenzoic acid	UV-B
Avobenzone	UV-A
Cinoxate	UV-B
Dioxybenzone	UV-B, UV-A
Homosalate	UV-B
Menthyl anthranilate	UV-A
Octocrylene	UV-B
Octyl methoxycinnamate	UV-B
Octisalate	UV-B
Oxybenzone	UV-B, UV-A
Padimate O	UV-B
Phenylbenzimidazole sulfonic acid	UV-B
Sulisobenzone	UV-B, UV-A
Titanium dioxide (physical)	UV-A/B, broad spectrum
Trolamine salicylate	UV-B
Zinc oxide (physical)	UV-A/B, broad spectrum

What are the differences between UVA, B and C?

UVA rays have the longest wavelengths, followed by UVB, and UVC rays which have the shortest wavelengths.

UVA and UVB rays are transmitted through the atmosphere.

All UVC and some UVB rays are absorbed by the Earth’s ozone layer.

So we usually come into contact with mostly UVA and a small amount of UVB.

UV radiation is classified by wavelength.

• UVB rays have a short wavelength that reaches the outer layer of your skin (the epidermis)
• UVA rays have a longer wavelength that can penetrate the middle layer of your skin (the dermis)

Both UVA and UVB rays can cause damage to your skin. Sunburn is a sign of short-term overexposure, while premature aging and skin cancer are side effects of prolonged UV exposure.
UVB causes the sunburn while UVA causes the premature aging of your skin.

How to choose your sunblock?

Sunblocks comes in a variety of forms.

• Lotions
• Oils
• Gels
• Sticks
• Sprays
• Creams

You can try several types and find the one which works and feels the best to you. For me, I find that creams and sprays give me a sticky feeling. I particularly like La Roche Posay Anthelios Extreme Fluide. It is a very light lotion. Especially good for people with oily skin. It can be applied to the face and body. Water resistant too.

All sunblocks/sunscreens should be applied at least half an hour before sun exposure to allow a protective film to develop, then reapplied after water contact and sweating. Recommended reapplication frequency is every 2 hours.

In general, 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 with different ingredients or a different form, e.g. lotion vs cream to see if you can tolerate better.

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.


Best way is to try a titanium dioxide or zinc oxide containing sunblock as they rarely cause skin irritation and provide very good broad spectrum UV protection.

FAQ: What is SPF and which rating is the best?

All sunblocks have a Sun Protection Factor (SPF) rating.

The SPF rating indicates how long a sunscreen remains effective on the skin. A user can determine how long their sunblock will be effective by multiplying the SPF factor by the length of time it takes for him or her to suffer a burn without sunscreen.

For instance, if you normally develop a sunburn in 10 minutes without wearing a sunscreen, a sunscreen with an SPF of 15 will protect you for 150 minutes (10 minutes multiplied by the SPF of 15).

So does this means that you should buy a product with SPF as high as possible? E.g. Sunplay SPF 130++.

Answer is NO. The protective effect increases insignificantly as the SPF increases. And the higher the SPF, the more chemicals you have on your skin. This increases your possibility of getting a skin allergy with the sunscreen. So the most optimal SPF you should go for is 50 or at least 30.

Although sunscreen use helps minimize sun damage, no product can completely blocks all wavelengths of UV light. Wearing sun protective clothing and avoiding sun exposure from 10 a.m. to 3 p.m. will also help protect your skin from overexposure and minimize sun damage.

FAQ: Do we really have to reapply the sunblock/sunscreen frequently? Does it mean that if the product is water-resistant, we do not have to reapply?

Water resistant sunblocks are available for active individuals or those involved in water sports. Some are "water-resistant" or "very water-resistant" or even sweat resistant.

• Water-Resistant sunblock maintains the SPF level after 40 minutes of water immersion
• Very Water-Resistant sunblock maintains the SPF level after 80 minutes of water immersion
• Sweat resistant is the same as water resistant.

So you still need to reapply the sunblock after the stipulated time period.

References:
1. www.dermatology.ucsf.edu/skincancer/General/prevention/Sunscreen.aspx
2. http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/Tanning/ucm116425.htm