Why Is Sunscreen Important And How To Choose One

a woman squeezing sunscreen from the bottle

Sunscreen is all the rage these days. But why is sunscreen important? Why do we need to protect ourselves from the sun?

But first, let’s understand exactly what it is that we need protection from.

UV Spectrum– and why is sunscreen important?

Part of electromagnetic spectrum of sun

The figure depicts a part of the electromagnetic spectrum. For the context of sun protection, we will focus on UV radiation only.  It comprises three different wavelength ranges, from longest to shortest being UVA, UVB and UVC.

UVA radiation comprises the major chunk of the UV spectrum (almost 95%) and can easily penetrate windowpanes. It is largely responsible for loss of skin elasticity leading to premature skin aging or photoaging. 

UVB radiation is the major cause of sunburns and skin cancers. It directly damages the DNA strand and the effects we see are immediate, for example erythema or reddening of the skin. Clouds and windows filter these rays.

UVC radiation is nearly entirely absorbed by the ozone layer of the earth’s atmosphere and hence doesn’t reach the surface, whereas the other two, UVA and UVB do.

Back to the question, why is sunscreen important? Short answer is to protect ourselves from the harmful UVA and UVB radiation and its effects down the line.

An easy way to remember is A for Aging and B for Burns.

Why is sunscreen important has two major aspects: UVA and UVB protection and we’ll take it up one by one.

What is an SPF value of the sunscreen?

In simple words, the protection against UVB radiation is measured by a product’s SPF value.

Contrary to popular belief, SPF doesn’t correlate with the time of sun exposure. You might have heard that a person can stay 15 times longer in the sun without burning while wearing sunscreen with an SPF 15. This is not true.

SPF correlates to the amount of sun exposure. It will take X amount of solar radiation to get burned after wearing SPF of X value. SPF is the ratio of Minimal erythemal dose (MED) of protected skin to MED of unprotected skin. MED is the amount of UV radiation that will produce a sunburn or reddening of the skin.

SPF=MED of protected skin/MED of unprotected skin

So, for the skin protected with SPF 50, it will take 50 times more solar radiation to cause a sunburn than it takes to burn unprotected skin.

According to the US Food and Drug Administration (FDA), the amount of solar energy is not just the time of exposure but the intensity of the sunlight too. For example, sun exposure for 1 hour at 9 in the morning may be equivalent to just 15 minutes of sun at 1 in the afternoon. The sunlight is more intense around midday than early morning or late evening; on clear days than cloudy ones; at lower altitudes than higher ones. Therefore, use adequate SPF and protective clothing including wide-brimmed hats, sunglasses etc.

A good rule of thumb for photoprotection is to stay indoors when the sunlight is most intense, ideally, 10 am to 3 pm.

How to choose an appropriate SPF value of sunscreen?

A higher SPF value corresponds to its effectiveness. This statement is true but to some extent. Let’s see how!

An SPF 30 is more effective than an SPF 15. Similarly, an SPF 50 is more effective than SPF 30. An SPF 15 can block 94% UVB radiation while SPF 30, 50 and 100 blocks 97%, 98% and 99% UVB radiation, respectively. However, some companies do charge a higher dollar amount for SPF over 50 but double the SPF value doesn’t double up your sun protection.

I recommend at least SPF 30 or more and to reapply every two hours or after sweating/swimming.

Word of caution: Please consult your physician before applying sunscreen on infants less than 6 months old. This is recommended by the FDA due to the lack of infant metabolism development.

Sun Protection Grade of UVA

Some of you might have also seen a PA rating on your sunscreen products. These ratings correspond to the UVA Photoprotection Factor (UVAPF) and is measured by the Persistent Pigment Darkening (PPD). These photoprotection grades are in accordance with the Japanese Cosmetic Industry Association (JCIA) guidelines. PPD response is measured to know how long it takes your skin to tan after UVA exposure.

UVB isn’t the only harmful component of the UV spectrum, however, traditionally, sunscreens were used to protect against UVB radiation only. But UVA also has a multitude of chronic effects, many of which are only visible after several years. 

As of 2011, FDA included the term “broad-spectrum” to include protection from UVA radiation. Any product that passes the critical threshold of ≥370 nm can be labeled as “broad-spectrum” and it means that the product protects against both UVB and UVA radiation. In the US, this critical wavelength test is the only basis of assessing UVA protection ability of a formulation.

The term “broad-spectrum” sunscreen means that the product prevents you from both UVA and UVB radiation.

Scientifically said, UVA photoprotection factor is the lowest UVA dose that produces a PPD response observed between 2­–24 hours after the end of UVA exposure. The protection grade ranges from some protection to extremely high UVA protection.

UVA photoprotection level

UVAPF valueProtection gradeUVA photoprotection level
2 to less than 4PA+Some protection
4 to less than 8PA++Moderate protection
8 to less than 16PA+++High protection
16 or morePA++++Extremely high protection

A PA+ rating will mean it takes approximately 2–4 times longer for the skin to get tanned compared to 8–16 times longer protection conferred by a PA+++ rating.

UVA Photoprotection (UVAPF)= MPPD of protected skin/MPPD of unprotected skin where MPPD refers to Minimal persistent pigment darkening.

Ideally choose a sunscreen with at least PA+++ or labeled as broad spectrum.

Why is sunscreen important? Let’s recap, shall we?

Sun protection is a no-brainer. It will help prevent skin cancers and premature aging. Seek shade when the sun is at its most intense. Use protective clothing and adequate protective filters a.k.a sunscreen to protect yourself from the sun rays to the best of your ability. Pick at least broad-spectrum SPF 30 sunscreen or the one with a high PA rating. Reapply after 2–3 hours and more frequently after sweating or swimming.

Well now you know why is sunscreen important and how to protect yourself! Click here to know more about the most common sunscreen mistakes and how to correct them! Also share this article with your friends and family!


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