You know that you need to wear sunscreen to protect yourself from the sun, but there are two questions standing between you and optimum sun protection:
- How do I choose the appropriate sunscreen?
- How do I apply it correctly?
This article is intended to clarify some of the terms you may encounter on sunscreen bottles, so that you can feel more confident in your selection. In addition, you will also learn how to professionally apply it to achieve maximum coverage.
What is SPF?
SPF stands for sun protection factor. The number is derived by dividing the amount of time necessary to produce skin redness (a mild sunburn) on sunscreen-covered skin by the amount of time necessary to produce that same sunburn on an area of skin not covered by sunscreen. In other words, if unprotected skin burns in 20 minutes, then a sunscreen with SPF 10 would delay the burn until 200 minutes had passed, providing 20x the protection. This is why it is important to reapply sunscreen (more on that later) as it does not prevent sun damage but merely delays its occurrence.
Is SPF 30 better than SPF 15?
The answer is “slightly, but not drastically so”. Here’s why: A product with SPF 15 allows 1/15th (6%) of the sun’s rays to penetrate your skin, meaning that 94% of the sun’s rays are blocked. That’s pretty close to 100%! By comparison, a product with SPF 30 allows 1/30th (3%) of the sun’s rays to penetrate your skin, meaning that 97% of the sun’s rays are blocked. So although a greater percentage of the sun’s rays are blocked by higher SPFs, the amount is not doubled, as the numerical values would imply. Some people feel safer using higher SPFs (and 97% is slightly higher than 94%), and there is certainly no problem with that approach. Whatever you decide on, you should always make sure that you sunscreen has an SPF of at least 15!
What types of rays does my sunscreen block?
The two types of radiation from the sun that we are concerned about are UVA and UVB. For a long time, it was thought that UVB alone produced sun damage. Today, we know that both UVA and UVB have substantial long-term effects on the skin! Often, sunscreens will allude to the type of UV radiation coverage they provide. Some phrases you may encounter are:
- Short wavelength blocker: UVB rays have shorter wavelengths than UVA rays. These sunscreens therefore target UVB rays. Ingredient with this capability = oxybenzene.
- Long wavelength blocker: UVA rays have longer wavelengths than UVB rays. These sunscreens therefore target UVA rays. Ingredients with this capability – avobenzone (aka Parsol 1789), ecamsule (aka Mexoryl SX), titanium oxide, and zinc oxide.
- Broad spectrum blocker: These sunscreens provide protection against both UVA and UVB rays. They combine the example ingredients mentioned above, along with some that were not mentioned. You should look for a sunscreen with broad coverage, as both UVA and UVB rays can lead to sunburns, photodamage, and skin cancer.
How do physical blockers differ from chemical blockers?
Chemical blockers act by absorbing UV rays so that they do not reach your skin. Examples include: para-aminobenzoic acid (PABA*) esters, cinnamates (octocrylene is in this class), salicylates, benzophones, and ecamsule. As mentioned above, these chemical blockers differ in what range of UV rays they absorb.
Physical blockers do exactly what their name implies: they physically block the sun’s rays, scattering the dangerous radiation away from your skin. Instead of referring to these agents as sunscreen, we should refer to them as sunblock. Physical blockers include titanium dioxide and zinc oxide. They are effective in blocking both UVA and UVB rays. These agents are generally thicker than chemical sunscreens.
*Note: PABA is an ingredient previously utilized in sunscreen preparations. Unfortunately, it produced allergic reactions in many people and is rarely found in newer sunscreens. PABA esters are derivatives producing less allergic reactions.
What is the best method for sunscreen delivery?
This depends on your skin type. People with dry skin may benefit from a cream. Those with oily skin may prefer a gel or a liquid. People with normal and combination skin may find that a lotion works best. Aside from skin type, ease of application may also influence your decision. Sprays are preferred by many people because of their convenient nature. On the other hand, sticks may be preferred when applying sunscreen to the lips and around the eyes.
What is substantivity?
Substantivity is a term used to describe how effective sunscreens are while you are sweating or participating in water activities. Sunscreens which best cover these activities are labeled “water resistant”, “waterproof”, or “sport”. Do note, however, that even these products need to be reapplied after 45 minutes of continuous activity.
How to apply sunscreen:
If you want to guarantee proper sun protection, follow these steps:
- Apply sunscreen approximately 30 minutes before stepping outdoors so that it can be adequately absorbed.
- Apply enough sunscreen! The recommended amount is one ounce, which is roughly equivalent to one shot glass. Chances are, this is more than you are used to applying, so it may take some getting used to.
- Apply thoroughly. Don’t miss key areas like the ears, nose, underarms, behind your knees, feet, and lips (a protective lipbalm or stick is useful for this purpose).
- Reapply frequently. Remember that sunscreens only protect you for a limited time. If you want to continue this protection, you need to re-apply on a regular basis! Because how frequently you reapply varies with what you are doing in the sun, it is generally recommended that you do so every 2-3 hours and after you swim or sweat.
If you are applying and reapplying appropriately, one 8-oz bottle of sunblock should only last you two weeks in the middle of the summer!