Home Chemistry Sunburns- Can you screen them?

Sunburns- Can you screen them?

Last updated on November 10th, 2020 at 03:23 pm

During summers what’s the most common thing everyone is more worried about apart from heat and sweat? Sunburns isn’t it? If you are a kid, your mother must be constantly reminding you to apply sunscreen lotions before you leave home. If you are a girl, you never forget to cover your face with a stroll. And if you are a guy, well I believe you hardly give about sunburns. Well, I am just kidding, just stating some preconceived notions.

I am sure, every one of you must have some sort of sunscreen creams or lotions for the summers in your cosmetics collections. These days many makeup cosmetics are available in the market claiming to provide sun protection and the ladies might consider this to a blessing in disguise of beauty. Well, it’s true up to some extent but when have ads shown the complete truth. In this article, I will be talking about sunburn, how it caused, and how effective sunscreens and cosmetics are towards it.

What is Sunburn?

It is a form of radiation burn caused by overexposure to UV radiation usually from the sun or any other source. The common symptoms of sunburn are reddish, hot, and mild pain on the skin along with general fatigue and mild dizziness. Excessive overexposure to ultraviolet radiation may lead to chances of skin tumors and life-threatening skin cancer.

Let’s have a look into the types of UV radiation we receive and their actions. There are 3 major categories the UV radiations from the sun can be divided, namely UVA, UVB, UVC.

In terms of wavelength, their wavelengths vary as UVA (315-400 nm) > UVB (280-315 nm) > UVC (100-280 nm). However, in terms of the energy they vary has UVC >> UVB > UBA.

UVC – These are high energy UV radiations emitted by the sun, but, nothing to worry about it, as almost all the UVCs are blocked by our ozone layer.

UVB – These are moderate energy UV rays and play a major role in causing sunburns. The UVB only penetrates the upper layer of the skin, i.e. the epidermis. It helps in the manufacture of Vitamin D in our body. But long exposure to UVB is a more potent cause of at least some skin cancers.

UVA – These are low energy UV rays. They can cause aging of skin cells and can also damage their DNA. These penetrate deeper into the layers of our skin up to the dermis and increase the risk of skin cancer.

Factors effecting Sunburns-

There are various factors associated with sunburns out of which the two major ones are-

Type of Skin- You will be surprised to know that our skin type is an important factor that determines the ease of getting a sunburn. According to the Fitzpatrick’s Skin Phototypes, our skin can be classified into 6 different types based on the response to UV radiations.

The UV Index- In simple terms the UV index indicates the risk of getting a sunburn at a given time and location. It depends on the time of the day, season, cloud cover, altitude, etc.

The UV Index is measured on a scale of 1 to 11, where 1-2 being low and 11 means extremely high. Usually, the UV index is comparatively higher during 10:00 am to 4:00 pm. One of the interesting ways to check how much UV radiation you are receiving is known as the shadow test. If the sun casts a long shadow of your body means you are receiving less UV and if it cast very small or no shadow means the sun is directly above you and you are receiving a high amount of UV.

What is Sunscreen?

Sunscreen is a lotion, gel, spray, or other topical product that absorbs or reflects the sun’s UV radiations. It basically slows down or better say prevent the effect of UV radiation on our skin. Today, there are types of sunscreen available in the market.

Sunscreen Products

Physical or Mineral Sunscreen- These sunscreens contain active minerals like titanium dioxide or zinc oxide. These appear a bit chalky and opaque, are difficult to remove but causes less irritation on the skin. Physical sunscreen protects your skin by simply reflecting the UV rays from the sun falling onto the skin. One of the major of these is their layer of protection gets easily damaged with sweat or water.

Chemical Sunscreen- As the name suggests these contain chemicals like avobenzone, octinoxate, and oxybenzone. These get absorbed into the skin and the protection is not damaged easily by water or sweat. But it can cause irritation at times on some types of skin. Chemical sunscreen protects by absorbing the energy from the UV rays from the sun and emitting it back as infrared rays.

Sunscreen: What is SPF?

SPF stands for “Sun Protection Factor”.

For chemical sunscreen, it is the ration of the time required to get a sunburn with sunscreen applied to that of the time required to get a sunburn on bare skin. For example, if you get a sunburn in 10 mins and you apply a sunscreen product with SPF 30, then you’ll get a sunburn in 300 mins. (provided your skin doesn’t get in contact with water, sweat, or you don’t wipe your skin).

SPF = (Time of sunburn with sunscreen) / (Time of sunburn without sunscreen)

For physical sunscreen, it is defined as the inverse of the percentage of UV rays absorbed by the sunscreen applied skin. For example, if a sunscreen of SPF 50 is applied then it absorbs 2% of the UV rays (100/50).

SPF = 1 / (percentage of UV rays absorbed by the sunscreen applied skin)

Sunscreen with SPF 10

How much protection do Make-up cosmetics with SPF provide?

So, even make-up cosmetics are now available with sunscreen protection as high as SPF 30. Great, isn’t it? Well not so great in terms of protection, let me tell you why.

On average, you need 1.23 grams of sunscreen lotion with SPF 30 to cover your completely and evenly and the pump of foundation contains approximately 0.11 grams of foundation. So, if you do the math, you need around 11 pumps of foundation with SPF 30 to get the same protection as a sunscreen lotion with SPF 30.

Now you can imagine how will your face look after applying 11 pumps of foundation or you can try it once. I’ll leave that to you. I haven’t tried it because I don’t want to make a ghost out of my face.

So, in my advice, it is better to rely on sunscreen products with SPF 30 or higher for protection from UV rays. Also, it is advised by most skin specialists to use chemical sunscreen if you are into swimming or sweating work such as sports or outdoor sales. Most importantly, while choosing a sunscreen product make sure it absorbs in your skin quickly, is oil-free, has a broad spectrum of protection (i.e. protects from both UVA and UVB rays), and is non-comedogenic (i.e. doesn’t clog the pores of your skin).

Do let us know, which sunscreen do you use in the comments.


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Abhijeet is a 4th-year Undergraduate Student at IIT Kharagpur. His major inclination is towards exploring the science behind the things of our day-to-day life.

Abhijeet Mahatohttp://scilynk.in
Abhijeet is a 4th-year Undergraduate Student at IIT Kharagpur. His major inclination is towards exploring the science behind the things of our day-to-day life.


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