Medically reviewed by Minimalist Health Specialist -  Written by Sritama Dutta (Medical Science)  on 12th Oct 2020

Want to know more about Sunscreens? Let's Play Twenty Questions

know more about Sunscreens

Sunlight is the primary source of vitamin D for our body's needs. However, staying out under the sun for long hours can have various detrimental effects on the skin's health.  


Overexposure to the sun can cause sunburns, dark spots and solar urticaria. The ozone layer acts as a natural barrier against the harmful Ultraviolet rays of the sun. Still, global warming and pollution have caused severe depletion of the ozone layer. This, in turn, has caused more UV radiations to reach us by passing through it. Long term exposure to these UV rays has shown to cause damage to our immune system, cause premature aging of the skin, and can even trigger skin cancer.

But staying out of the sun cannot be a healthy option. It may have its risks, but sunlight also has plenty of benefits to our body. It is responsible for our psychological well-being.  

So, how should you protect yourself from the sun rays and also enjoy basking under the sun?  

The simple answer is Sunscreen. It shields your skin from the harmful effects of the sun but lets it absorb its beneficial effects.

However, many questions linger in our minds about sunscreens, its ingredients, benefits, and how it works. We have done explicative research to answer all the concerns you may have about sunscreens.  

Here are twenty well-researched and data-backed answers to twenty frequently asked questions about sunscreen:

1. What does SPF mean?

Sun Protection Factor (abbreviated as SPF) is the measure that determines how much solar energy or sun radiation is required to cause damage to the skin when the skin is protected by wearing sunscreen compared to unprotected skin.

The number beside SPF can help you to determine how much time you can spend under the sun while wearing sufficient sunscreen. This needs a pretty simple formula:

Time your skin takes to develop a burn × SPF number = Maximum time of safe sun exposure.

It is seen that unprotected skin takes about 10 minutes to develop a sunburn.
So, if you are using sunscreen with SPF 30, it means you can be out in the sun without any damage for (10×30=) 300 minutes. 

2. What does "Broad Spectrum" sunscreen mean? 

The Ultraviolet rays in the sunlight are of different types that vary in their wavelengths. They are UVA and UVB rays that penetrate the earth's atmosphere and can be harmful to you.

UVA and UVB together make a deadly combination that can cause premature skin aging and sunburns and even induce skin cancer.

Another type of ray known as UVC rays are also present, but as they have the shortest wavelength among the three, it gets absorbed by the ozone layer and has no effect on our skin.

As per the FDA (Food and Drug Association), any sunscreen labeled as "Broad Spectrum" indicates that it is effective against UVA and UVB and protects your skin from all the damaging ultraviolet rays.   

3. What are the different types of sunscreen? 

Sunscreens are usually of two types, and they differ in their mechanism of action on the skin:

  • Mineral or Inorganic Sunscreen  
  • Chemical or Organic Sunscreen. 

The mineral sunscreen blocks the UV rays from reaching your skin by building a protective barrier on the surface of the skin. The chemical sunscreens absorb into your skin instead of forming a barrier and chemically converting the UV rays into heat.  

4. Is SPF 30 or SPF 50 better?

Studies have shown that SPF 30 prevents 97% of UV rays from reaching your skin, whereas SPF 50 prevents 98% of UV rays from affecting your skin. The 1% difference might seem negligible, but once you realize that it means about 50% of harmful UV rays can reach your skin when using a lower SPF, it builds up a huge discrepancy.

Also, using SPF 50 means that you can spend almost 3 hours longer under the sun without reapplication of sunscreen than SPF 30. 

5. What do sunscreens contain? 

The ingredients differ in the two types of sunscreen available in the market.

The mineral sunscreen is composed of zinc oxide and or titanium dioxide.

The chemical sunscreens are usually made by combining two to six active organic compounds like: 

  • Oxybenzone 
  • Avobenzone 
  • Octisalate 
  • Octocrylene 
  • Homosalate and,
  • Octinoxate

6. Are there any harmful ingredients in Sunscreen? 

According to the FDA, certain chemicals are graded as "Generally Recognised as Safe and Effective" (abbreviated as GRASE). These ingredients are Titanium Dioxide and Zinc Oxide that are used in mineral sunscreen.

However, certain chemicals can be potentially damaging to our environment rather than our body. These are: 

  • Oxybenzone: It is often used in broad-spectrum sunscreens. Certain studies have shown that it can cause bleaching and poisoning of coral reefs. Research done in 2017 found that oxybenzone can cause allergic reactions on the skin. It has also been claimed that oxybenzone is a potential endocrine-disruptor but lacks much evidence.  
  • Avobenzone: This has similar risks as associated with oxybenzone. It also penetrates the skin and increases free radicals in dermal layers, increasing skin cancer risk. It can also cause photoallergies.  
  • Homosalate: It is a ubiquitous ingredient used in chemical sunscreens. Though it's limited at a 10% concentration in sunscreen formulas, homosalate can penetrate your skin and accumulate in the dermal layers, which further causes endocrine disruption.
  • Octinoxate: This is another commonly used UV filter that can systemically absorb into our body and act as an endocrine disruptor. It is also listed as a harmful ingredient that causes coral bleaching. 

7. What is the difference between UV-A and UV-B? 

Among the electromagnetic radiations that can penetrate the ozone layer and reach the earth, UVA and UVB rays are two of the most harmful ones. UVA has the longest wavelength, while UVB has a somewhat lesser wavelength. About 95% of the sunlight reaching us are UVA rays, and the remaining 5% is UVB.

UVA rays affect the underlying skin cells below the epidermis. Its short-term effects include tanning and sunburns and can also cause premature aging, wrinkles, and even skin cancer if exposed to it for a long duration.

UVB rays affect the superficial skin layer. Its short-term effects include sunburns and blistering and aging and inducing carcinogenic effects on a long exposure.  

8. How does Sunscreen work?

The Mineral Sunscreen forms a film over the superficial layer of skin and reflects the sunlight, not allowing it to affect the skin.

The chemical sunscreen absorbs the harmful rays and converts them into heat by a chemical reaction and prevents the rays from seeping into the skin.  

9. What are the benefits of wearing Sunscreen? 

  • Wearing sunscreen protects you from the harmful rays of the sun like UVA and UVB rays.
  • It allows you to enjoy the benefits of natural sunlight but prevents premature aging, sunburns, and tanning. 
  • Reduces the risk of developing skin cancer.
  • Prevents drying of skin by retaining the moisture inside your skin layer.  

10. What are the risks of using sunscreen?

  • Applying cream-based sunscreen can give your skin a greasy appearance. Using a spray-sunscreen can be a good alternative.  
  • Chemical sunscreens that get absorbed in the skin layer can irritate the skin and aggravate breakout and acne. If you have acne-prone skin, using a non-comedogenic mineral sunscreen is a better choice.  
  • Sunscreen can interfere with the production of Vitamin D in our body. As it blocks maximum sun rays and the harmful radiations, it reduces the generation of Vitamin D in our body, causing a severe deficiency in the long term. If you have to go out in the sun a lot, then it's best to take Vitamin D supplements.
  • The ingredients of sunscreen can also cause allergic reactions. It's wise to have a patch test before you apply the sunscreen.

11. When should you wear Sunscreen? 

For the sunscreen to be effective at its maximum, it is recommended by dermatologists to apply sunscreen about 30 minutes before you step out in the sun. The ingredients will take some time to penetrate your dermal layers and show its action against blocking the harmful sun rays.  

12. How much sunscreen cream/lotion should you apply? 

The required amount of sunscreen that should be applied to cover all of your skin is about 1 ounce for an adult. The recommended thickness that must be used on the skin should be 2 mg/cm2. 

13. How often should sunscreen be applied? 

The ingredients of sunscreen break down gradually under direct exposure of Sun. It is a safe practice to reapply sunscreen lotion every two to three hours when you have plans to spend the day outdoors.  

14. Should sunscreen be used even on cloudy days or when staying indoors? 

Even when the sun is not out, or you are planning to stay indoors all day, sunscreen is equally important. Sun rays will beam down through the windows, and even on cloudy days, about 80% of UV rays seep through the atmosphere. It is recommended that the daily application of sunscreen is the best practice. It significantly lowers the risk of skin cancer and premature aging.  

15. Is the sunscreen combined in makeup sufficient for your skin? 

If you prefer to use makeup products with SPF protection, it is good, but certainly not enough for your skin.

The amount of sunscreen in your foundation is about 7 times lesser than your skin's required amount. So, it is recommended to layer your skin with Sunscreen of minimum SPF 30 before applying makeup.

16. How is Sunblock different from Sunscreen? 

Chemical Sunscreens, when rubbed on the skin, penetrate the dermal layers and absorb the harmful sun rays.

However, sunblocks are usually the physical sunscreens that contain titanium dioxide or zinc oxide or both.

It forms a film over the skin that blocks or reflects away the sun rays. It does not have to be rubbed but just slathered. Sunblocks leave a white cast on your skin, but sunscreen gets absorbed completely.  

17. Does Sunscreen lose strength over time? 

All sunscreens regulated by the Food and Drug Administration (FDA) have a shelf-life of three years. Whenever you use sunscreen or pick a new one from the store, make sure to look at the expiration date marked on the level.

Sunscreens stay in good condition if stored in a cool, dark place with little humidity. Exposure of the product to excessive heat or direct sunlight can reduce its efficacy.  

18. Is water-resistant Sunscreen necessary? 

If you plan on dipping into the water, water-resistant sunscreens are the best option for a beach day. However, sweating can also cause the sunscreen to wash off eventually. A water resistant sunscreen binds better to your skin layer and does not wash off fast.  

19. Is sunscreen safe for babies? 

Baby skin is more delicate than an adult's skin. So it is better to avoid using sunscreen on your baby younger than 6 months. To keep them safe from the sun, cover them up with light-colored clothes and try keeping them under shade. However, you can safely apply sunscreen on infants older than 6 months. 

20. What type of sunscreen should you use? 

Sunscreen is a product that you need to use in your everyday regime. So, it would help if you chose a broad-spectrum and water-resistant sunscreen with a minimum SPF 30. However, choosing according to your skin type is also necessary.  

Liquid error (sections/pf-ac5ac7c0 line 78): product form must be given a product


Sunscreen is undoubtedly an essential component of your daily skincare regime.
We are hopeful this 101 on Sunscreen article has been of help and has addressed all your concerns about using sunscreen.