Sunscreen tips

Growing up in the 1970s and 1980s, we had a different relationship with the sun. We didn’t think we looked good or ”healthy” unless we had a tan. So we spent many hours in our teens and 20s laying out in the sun – burn, peel, repeat …… until tan look hold. But for decades it is absolutely proven that sun causes most skin cancers. We also know that in some cases, skin cancer can be deadly. Although some people are concerned about the safety of sunscreens, the truth is that they help protect you from the potentially deadly risk from the sun. Two recent important Australian studies showed more convincingly than ever that melanoma (the deadlies form of skin cancer) was reducer by 50 percent in those who used sunscreen daily. That’s huge. And of course wearing sunscreen can prevent sunburn and reduce your risk of premature aging. So keep slathering on the sunscreen!

What should I protect against?

Sunlight consisits of two types of harmful rays that reach the earth – UVA rays and UVB rays. Sunlight contains 20 times more UVA than UVB radiation. Overexposure to either can lead to skin cancer. In addition to causing skin cancer, here’s what each of these rays do:

• UVA rays (or aging rays) penetrate the deeper layers of the skin, harm the connective tissue and the skin begins to lose its elasticity. In this way they can prematurely age your skin, causing wrinkles and age spots. These rays can pass throug window glass.
• UVB rays (or burning rays) are the primary cause of sunburn and are blocked by window glass.

The SPF on the packaging informs you how well sunscreen will protect skin from UVB rays. If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximatelly 150 minutes (a factor of 15 times longer). This is a rough estimate that depends on skin type, intensity of sunlight and amount of sunscreen used. It is also important that SPF scale is not linear: SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97% os UVB rays, SPF 50 blocks 98% of UVB rays. So, one way of looking at this is that SPF 30 sunscreen only gives you 4% more protection than SPF 15 sunscreen. Sunscreens with really high SPFs, such as SPF 75 or SPF 100, do not offer significantly greater protection than SPF 30 and mislead people into thinking they have more protection than they actually do.

Please note that you choose a sun cream that protects against both UVB and UVA radiation. UVA radiation doesn’t burn you, so you don’t see any warning signs from your skin either. But UVA rays are potentially more damiging than UVB rays. According to the new regulation the UVA protection factor must be at least 1/3 of the UVB protection factor. Products achieving this display a circle with the letters UVA inside on the packaging. Unfortunately not every manufacturer is at this stage yet. High SPF sunscreens usually offer far greater UVB than UVA protection, thus offering a false sense of full protection.

Another interesting fact is that not only UV radiation causes damage but also infra-red radiation. Infra-red causes free radicals to form and damages the collagen. Sun filters are ineffective against this radiation but antioxidants are effective. In order to limit the damage which is already present, it is worth applying antioxidants onto your skin.

Application of suncream: how to do it right

The recommended amount of sun cream is 2 milligrams per cm². Shocking but true: most people under-apply sunscreens, using ¼ to ½ the amount required. Using half the required amount of sunscreen only provides the square root of the SPF. So, a half apllication of an SPF 30 sunscreen only provides an effective SPF of 5,5. Since the required 2 milligrams per cm² is almost imposible to wipe away, always remember that you are probably less protected than you think.

Follow the guidline of ”1 ounce, enough to fill a shot glass”, which dermatologists consider the amount needed to cover the exposed areas of the body. Adjust the amount of sunscreen applied depending on your body size.

Apply sunscreen to dry skin 15 minutes before going outdoors.

Reapply suscreen approximately every two hours, or after swimming or sweating.

Physical vs. chemical sunscreen

There are two general types of sunscreens, physical and chemical ones. Physical sunscreens use physical UV filters, while chemical sunscreens use chemical filters. There are also hybrid sunscreens that contain both physical and chemical sunscreen actives. Physical 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 also scatter sun rays, but still mostly just absorb them. The physical filters are generally photostable, but some of the chemical filters are not. Avobenzone for example is notoriously unstable. However, it can be stabilized when formulated in conjunction with other UV filters. While physical filters are generally safe, chemical filters tend to be more irritating to skin, some can cause allergic reactions. If they get into your eyes, they can make your eyes sting and water. Physical filters start protection immediately upon application, but with chemical filters you must wait 20 minutes after application for effective sun protection. Chemical filters usually 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. One of the disadvantages of the physical sunscreens is that they are thick and opaque, therefore may be hard to apply and tend to leave a white cast or tint. These types of sunscreens rub off more easily and must be frequently reapplied. The chemical filters on the other hand are colorless, odorless, usually runny, which provides them a better cosmetic appearance.

• Physical UV filters: Titanium dioxide (TiO₂), Zinc oxide (ZnO)
• Chemical UV filters: Octylcrylene, Avobenzone, Octinoxate, Octisalate, Oxybenzone, Homosalate, Heloplex, 4-MBC, Mexoryl SX and XL, Tinosorb S and M, Uvinul T 150, Uvinul A Plus

Is sunscreen from last year still good?

Sunscreens are designed to remain at original strength for up to three years. This means that you can use leftover sunscreen from one year to the next. Some sunscreens include an expiration date – a date indicating when they’re no longer effective. Discard sunscreen that is past its expiration date. If you buy a sunscreen that doesn’t have an expiration date, write the date of purchase on the bottle and be sure that you throw it out within three years. Also, discard sunscreen that has any obvious changes in colour or consistency.

Keep in mind that if you use sunscreen generously and frequently, a bottle of sunscreen shouldn’t last long. Generally, a liberal application is approximatelly 30 milliliters – the amount in a shot glass – to cover exposed parts of the body. You might need to apply more, depending on your body size. If you have 120 milliliter bottle, you’ll use about one-fourth of it during one application.

Addressing the concerns some people have about certain ingredients in sunscreens

Attention has focused most on the ingredient oxybenzone and whether it is a hormone disruptor. One study showed uterine growth in rats. But if you look at that study, they fed the rats a huge amount of this chemical over the course of four days. To duplicate that amount in humans would take applying sunscreen all over the entire body every day for 70 years. It was not an accurate model for what a human would be exposed to.

We know that oxybenzone is absorbed into the body to some degree, and is excreted in urine and breast milk. We don’t know the implications of its use in women who are pregnant or breastfeeding, because that type of clinical study can’t be performed on this group. So, out of an abundance of caution, I suggest they use a zinc- or titanium-based sunscreen.

Other claims about sunscreen ingredients have been floating around on the internet but are not backed up by hard science. For example, you may have read that sunscreen containing vitamin A, or retinyl palmitate, can cause skin cancer, but there’s no data to support that. People who use those sunscreens, or any sunscreens, can still develop skin cancer, and the most likely cause is skin damage from sun exposure in earlier years. And protecting yourself now could prevent skin cancers in the future.

About skin allergy or sensitivity caused by sunscreen

When you think about allergy or sensitivity to a sunscreen, don’t assume it’s because of the active ingredient. A true allergy to the active ingredients is quite rare. It’s far more common to experience sensitivity to the inactive ingredients in sunscreens. There are emulsifiers, preservatives, fragrances, plant extracts, antioxidants and other ingredients that can cause contact dermatitis, including “natural” ingredients. Some products have many inactive ingredients, and it can be difficult to identify which one is causing the trouble. An allergic reaction typically takes three to five days to develop. I often counsel my patients who have a sunscreen sensitivity to use the inorganic sunscreens — those that contain zinc oxide and/or titanium dioxide, and with as few other ingredients as possible.