Sunscreen: Your First Line Of Defense

Sunscreen is without a doubt most dermatologists’ favourite product to use and talk about.

Before you start getting fancy with washes, toners and serums, a good sunscreen should be your first line of defense.

Sunscreen not only protects against skin cancer development, but also has a role in preventing pigmentation, our photodermatoses and of course ageing.

Seems simple enough, but I’m sure you’ve been stuck standing in front on a full sunscreen aisle asking;

How do I choose a sunscreen?

  1. Chemical or mineral?

  2. How much do I need to use?

  3. Is once a day enough?

Choosing a sunscreen:

The sun emits 3 types of ultraviolet (UV) radiation; A, B and C. While C doesn’t penetrate the earths atmosphere A and B are problem enough.

UVA rays account for 95% of rays and can penetrate through clouds and even glass. They are longer rays and penetrate the deeper layers of your skin (dermis) contributing to premature ageing and wrinkles (photoageing).

UVB rays are typically shorter and typically only reach the outer layers of your skin (epidermis). These rays contribute to redness and delayed tanning response we see after being in the sun. This response signals DNA damage and an increased risk of developing skin cancer.

You therefore need a sunscreen with both UVA and UVB protection.

Studies have shown that SPF30 if applied correctly absorbs 96.7% of UVB and SPF 50 90%.

This means your sunscreen should be at least SPF 30, with marginal benefit obtained by increasing your SPF value provided you are applying it sufficiently.

UVA protection will be marked as “UVA-PF+” or they may state broad-spectrum on the container meaning both UVA and UVB.

Chemical or mineral?

Chemical sunscreens are water or oil soluble and work through chemical filters which absorb UV rays diverting the energy away from the cells. These formulations are often thinner and spread across the skin more easily.

Physical sunscreens are insoluble molecules often of zinc or titanium oxide. They work by diverting the suns rays away from the skin. They are great for children, pregnant women, and those with sensitive skin. They however may be a bit more difficult to rub in and leave a white cast on the skin.

How do I ensure I am getting adequate protection?

Sunscreen should be worn every day irrespective of the weather outdoors or if you plan to be indoors all day.

The appropriate amount is key. You need to be using 2mg/cm2 which translates to a R5 coin or ½ teaspoon on your face and 2 golf ball size amounts for the body (1 above the waist and 1 below, front and back each need 2).

Sunscreen Should be reapplied every 2 hours when actively in the sun and after swimming. Every 4 hours should be sufficient on an average day.

Ultimately the best sunscreen is one falling within these parameters in the formulation that you like to use and that you can afford in large amounts. There is nothing worse than splurging out on a sunscreen and then feeling as though you need to use it sparingly.

Remember that you can also enhance your sun protection by avoiding the sun during peak hours (10:00-14:00), seeking shade or making use of sun protective clothing.

Compiled by: Dr. Lauren Knight


MBChB (UCT) | Msc | FCDERM | MMed (Derm)

Dr. Lauren Knight specializes in medical, surgical, and cosmetic dermatology across all ages. She enjoys working with her patients to not only treat and hopefully cure their conditions where possible, but also to lessen the burden the condition may be placing on them.