What Is SPF - Different Types Of Protective Sunscreens

Sunscreen 101 

Remember back when sunscreen options were non-existent, and everyone just reached for a bottle of Coppertone? Those days are definitely over as new products and formulations are constantly introduced to the market. But which one do you recommend? Are all sunscreens equal? We will break down the facts to help you discuss different sunscreen options. 

First, Some Sunscreen Basics

What is SPF?

SPF stands for sun protection factor, and is a numerical value assigned to a sunscreen product based upon its ability to prevent sunburn. The SPF on the label indicates how well the product protects the skin from the sun’s damaging rays. It is important to note that the testing to determine a product’s SPF is done using only UVB and not UVA. Therefore, SPF really only reflects the level of UVB (burning) protection and not UVA (aging) protection.

Is higher or lower SPF better?

In regards to SPF, a higher number confers better sun protection over a lower number. SPF 30 blocks approximately 97% of the sun’s UVB; a higher number would block more and a lower number would block less.

SPF is commonly misinterpreted to correlate with duration of effect, and there are formulas people have used to calculate that length of time. However, this is not correct and such calculations could lead to under application of sunscreen and inadequate sun protection. A higher SPF does not provide longer protection than a lower SPF.

Who needs it?

The American Academy of Dermatology currently recommends that everyone wear sunscreen with a minimum SPF 30 any time the individual is outside.^[2] This includes overcast days and quick trips to the grocery store. Those with fairer complexions can opt for higher SPF if they want more protection.

Chemical vs. Physical Suvnscreen Ingredients

These are the two main categories of sunscreen, and they determine what active ingredients in the sunscreen protect the skin from harmful UV rays.

A physical sunscreen uses minerals such as zinc oxide and titanium dioxide to create a physical barrier on the skin and deflect ultraviolet (UV) rays from the sun.^[1]

A chemical sunscreen uses chemicals (like the name suggests) to absorb UV rays, which damage the chemical bonds of the active ingredient instead of the underlying human tissue. This process causes the sunscreen itself to break down over time. The most common active ingredients for chemical sunscreens include oxybenzone, octinoxate, avobenzone, octisalate, octocrylene, and homosalate.^[1]

Physical sunscreen

This is the original type you picture when you think of a lifeguard with a big, white glob of sunscreen on his or her nose.

Pros:

• Provides broad-spectrum coverage (protects against UVA and UVB)
• Considered safe for all skin types
• Non-comedogenic

Cons:

• Very often is visible, leaving white residue on the skin
• Can get rubbed off easily
• Requires frequent reapplication

Chemical sunscreen

These are newly developed types of sunscreen and currently include most sunscreens on the market today.

Pros:

• Easier to rub in and invisible on skin
• Can be worn under or mixed with makeup

Cons:

• May irritate sensitive skin types
• Can sting if it gets in the eyes
• Can be comedogenic
• Requires frequent reapplication 

Water Resistance

Water resistance of sunscreen refers to how long a sunscreen remains effective while in water during testing:

• Water Resistant sunscreen = 40 minutes in water
• Very Water Resistant sunscreen = 80 minutes in water.

These sunscreens require reapplication every 40 or 80 minutes, respectively, unless the skin remains dry. Sunscreens that use either physical or chemical based sunscreen ingredients can be rated as water resistant or very water resistant.

Forms of Sunscreen

There are so many different choices for sunscreen applications beyond the classic lotion. According to the American Academy of Dermatology (AAD), the most common sunscreen products being used in the United States today are lotions/creams, gels, sticks, and sprays.^[2]

Lotion/Cream^[2]

This is the tried-and-true form of sunscreen that’s been around the longest. These can easily be found in stores and chances are, most people have a bottle of this somewhere in their home.

Pros:

• Cheaper and readily available
• Considered the best for dry skin and face
• Easy to quantify and keep track of where it has been applied
• More choices in brands and ingredients
• Most researched and most evidence

Cons:

• Can take a long time to rub in
• Not great for application on hard to reach places (ex. back)
• May leave an undesirable residue on the skin
• Can be messy 

Gel^[2]

Gel sunscreens are a relatively new concept growing in popularity. These are water-based formulations less likely to leave the typical “sunscreen” feel on the skin, and may be preferable for people with oily skin.^[3] 

Pros:

• Doesn’t leave greasy residue on skin
• Easier to rub in
• Good for oily or acne-prone skin
• May be easier to apply on hairy regions such as the scalp or male chest

Cons:

• Less water/sweat resistant
• Can cause stinging (in eyes and on skin)
• More expensive than cream/lotion
• Less research on application characteristics

Stick^[2]

Stick sunscreens can be extremely convenient for quick mess-free application and offer an effective way of protecting vulnerable lip skin.^[4]

Pros:^[3]

• Convenient application
• Easy-to-use around the eyes
• Relatively mess-free
• Can come as lip balm

Cons:

• Not good for application on body
• More expensive than cream/lotion
• Hard to quantify how much is applied

Spray^[2]

Current trends show rates of spray sunscreen purchases are on the rise, and it is projected that spray formulations will overtake lotions/creams as the most popular form of sunscreen in the near future.^[5]

Pros:

• Easy and fast application
• Doesn’t require assistance to apply to back and other hard to reach areas
• Can be less greasy than lotions
• Can be applied to scalp
• Readily available

Cons:

• More expensive than lotion
• Hard to quantify how much is applied
• Harder to gauge which areas have been covered
• Can easily be inhaled or sprayed into eyes and mouth
• May be flammable
• May lose a significant amount of product during application, especially in windy areas 

Application

Multiple studies have shown that regardless of the form of sunscreen used, people routinely do not apply sufficient amounts to provide the full stated SPF and sun protection.^[6,7] This is especially true of children self-applying their sunscreen.^[8] 

Quantity

The current recommendations state that 2 mg/cm² of sunscreen is necessary for adequate sun protection.^[7] This amount is difficult for most people to conceptualize, so the AAD translates that amount to about 1 oz (enough to fill a shot glass) for most full-grown adults.^[2] If only applying to the face and neck, 1/3 of a teaspoon should be enough (calculation: 5% of body surface area x 1 oz. = 0.05 oz. = 0.3 tsp). Of note, there isn’t a consensus of how to best estimate the amount of sunscreen you are applying with sprays, gels, and sticks.

Double application is best

Regardless of the type of sunscreen being used, a good technique for attempting adequate coverage is to apply it in two coats. One study showed a second coat of sunscreen led to an 11% increase in coverage over a single coat (80% to 91%) and brought the applied thickness closer to the 2 mg/cm² goal.^[9] 

Reapplication

The AAD recommends reapplying sunscreen every 2 hours and immediately after swimming or sweating.^[2]

Rub it in

Despite the temptation to be “hands free” when using spray-on sunscreen, it is important to fully rub it in, as one would with any other form of sunscreen. This decreases the chances of missed areas of coverage.^[10]

The FDA Weighs In

In February 2019, the FDA announced revised rules that could impact sunscreens and their allowed ingredients. Here is a summary of the updated regulations.

Ingredient safety:^[11]

• Zinc oxide and titanium dioxide are the only active ingredients considered generally recognized as safe and effective (GRASE).
• PABA and trolamine salicylate are considered NOT GRASE and should be avoided.
• All other active ingredients (such as those in chemical sunscreens) have insufficient evidence to prove they are GRASE and more data is necessary.

Forms of sunscreen:^[11]

• Acceptable forms of sunscreen include “sprays, oils, lotions, creams, gels, butters, pastes, ointments and sticks.”
• At this time, powder forms of sunscreen do not have enough evidence to be considered GRASE.
• Wipes, towelettes, body washes, and shampoos are other newly proposed forms of sunscreen but currently have the least evidence.

Broad-spectrum protection:^[11]

• New regulation will require that all sunscreen containing SPF 15 or higher include broad-spectrum (UVA and UVB) protection.

Labelling:^[11]

• There will be stricter guidelines requiring more transparent and easier to understand labelling.
• This includes clearer listing of active ingredients as well as transparency in products that have not been proven to reduce skin cancer risk.

Insect repellents:^[11]

• All products that combine sunscreen with an insect repellent are NOT considered GRASE and should be avoided. 

Practical Tips

1. If ingredients are confirmed to be generally recognized as safe and effective (GRASE) are important, recommend physical sunscreens containing zinc oxide and/or titanium dioxide.
2. The best sunscreen is the one you are going to use so lotions/creams, sticks, sprays, and gels can all be efficacious.
3. Sunscreen must always be fully rubbed in to allow it to absorb and two applications back-to-back can best ensure the entire body is covered.
4. No need to wait 20-30 minutes after application before sun exposure; both chemical and physical sunscreens are effective immediately.