Going through isles of sun care products, you probably noticed that many offer "Complete UVA/UVB protection". Why do you need to be protected from both, and what is the difference between the two?

UVA and UVB are two types of ultraviolet rays that change physical and chemical condition of the skin. They produce different effects, but at the same time enhance each other’s action.

UVB rays are the burning rays that cause immediate skin reaction - redness and swelling that you see within hours of sun exposure. As you look at yourself in the mirror, you are not likely to think of your sun kissed skin in these terms. It definitely looks better now that there is a glow to it and wrinkles seem to be less visible. But the look is deceiving. The glow is caused by increased blood flow to the skin as a rescue response to repair the damage, and wrinkles are less visible because your skin has just suffered an injury and is puffed.

UVB rays are responsible for skin cancer and cataract.

UVA rays stimulate production of melanin, the skin pigment. Melanin is formed in deeper skin layers and reaches the surface in two-three days. This is when you see that you've got tan. Unfortunately, there is little to be proud about, as tanning is what your body does to protect itself from the sun. It is a reaction to potentially dangerous conditions that you expose yourself to.

If you are trying to avoid freckles, age spots, pregnancy mask or any other type of skin discoloration, UVA rays are your first enemy. It is important to remember that while glass windows block UVB rays, they do nothing to shield you form UVA rays.

UVA rays were thought to be less damaging, and common belief was that safe tanning was possible: you block UVB and enjoy the bronzing effect of UVA rays. Wrong! Recent research proves that UVA rays may be even more dangerous than UVB. They reach deeper into the skin layers and contribute to photoaging and development of melanoma, a very dangerous type of skin cancer.

Photoaging is aging of the skin caused by sunlight. Collagen, a large protein, is the main skin building block. 90% of the skin mass is collagen which contributes to skin’s firmness,strength and elasticity. Skin has the ability to renew collagen fibers: grow new ones and dissolve those that are damaged. UV rays interfere with these chemical reactions and suppress collagen production while stimulating collagen destruction. In our 20’s, collagen production slows down, and eventually all that the skin is left with is damaged collagen, which is not as flexible and cannot perform its original functions. The skin loses its elasticity and forms wrinkles.

Sooner or later, wrinkles happen to everyone due to natural skin aging and gravity. However, without proper sun protection, skin ages a lot faster, and unfortunately, the damage is irreversible.

There are two types of protection used in skin care products: physical and chemical, where physical block reflects sun rays, and chemical absorbs them, similar to melanin, before they can do any harm.

Physical sun screens include zinc oxide and titanium oxide, with zinc oxide (aka Z-Cote) being more powerful. Now creams with Z-Cote are available in wearable form, when they do not look like white paste, but spread into an invisible barrier that reflects both UVB and UVA sun rays.

Most powerful UVB screen is PABA, but it is not perfect for everyone as it often can cause an allergic reaction. Other chemical screens are:

· Cinnamates absorb UVB.
· Benzophenones absorb UVA.
· Anthranilates absorb UVA and UVB.

Usually, your sunscreen product will contain several protective ingredients, as combining them provides better shield, according to research.

FDA requires each batch of sunscreen products to go through SPF testing to ensure the effectiveness of the product. At this time, sun protection factor applies to UVB rays only as more research is necessary to determine the standards for UVA protection.

As a rule, SPF number translates into the amount of time one can safely be in the sun without burning. If you are an individual with fair skin and burn in 10 minutes if unprotected, SPF 15 will allow you to stay in the sun 15 times longer (150 minutes). If your skin is dark and you burn in 30 minutes, the same product will protect you for 450 minutes.

This formula is very approximate and does not provide for real life conditions: wind, humidity, season, your location, etc. Humidity and wind, for example, maximize the power of sun rays, and your SPF 15 lotion may offer much less protection when used on a breezy day or near water. Proximity to the equator and elevation should not be forgotten: the closer you are to the sun, the stronger its effect.

Reapplying your SPF often provides better protection than purchasing a product with a higher SPF number. SPF protection does not actually increase proportionately with an SPF number. Under lab conditions, SPF 2 equals 50% absorption of burning UVB rays, SPF of 15 indicates 93%, and SPF 30 and higher - 97% absorption.

As you see, some sunrays will still reach your skin, even if you use lotion with a high SPF number. To shield these remainingrays, use other means of sun protection: clothes, hats, umbrellas and shades. Please remember that many surfaces - snow, sand, water, concrete - reflect sun rays, so don't be surprised if you got tan or burn even though you spent most of your beach day under umbrella.

(C) Natalie Katsman, 2004