Why a dermatologist with sensitive skin uses only mineral sunscreen, which chemical filters cause stinging, and what SPF and PA actually mean.
Hello. This is Dr. Lee Yumin of MeSOnBom Clinic.
Summer has arrived in earnest, and the midday sun is sharp.
As temperatures rise and outdoor activity increases, sunscreen is the first essential for skin health.
Its importance is now widely understood, and many people apply it diligently every day.
But asked whether the sunscreen they are using actually suits their skin type, quite a few hesitate.
Choosing the right one among the many products available is harder than it looks.
I have sensitive skin myself, with atopy, asthma and rhinitis, so I apply strict criteria when choosing.
To put my conclusion first: I use only mineral (physical) sunscreen.
Let me explain from a medical standpoint why I avoid chemical filters, and how to check the right figures for you.
Sunscreens divide broadly into mineral, chemical and hybrid types by their filtering principle and ingredients.
To find the product that suits your skin, it helps to understand the mechanisms exactly.
The main ingredients are minerals such as titanium dioxide and zinc oxide.
They form a fine protective film on the surface that physically reflects and scatters UV light, like a mirror.
Advantages: because there is no chemical reaction, protection begins the moment it is applied. Absorption into the skin is low, so irritation is minimal and it is safe.
Disadvantages: the white cast, where the skin looks pale. The texture is also somewhat dense and drying, so it spreads less easily and is less popular.
Chemical sunscreens consist of compounds such as octinoxate, avobenzone, octocrylene and oxybenzone.
Rather than reflecting UV light at the surface, they absorb it into the skin and convert it into heat through a chemical reaction, releasing it outward.
Advantages: no white cast at all, and they spread softly and smoothly like a lotion, making them good under makeup.
Disadvantages: because a chemical reaction is required, protection only becomes active about 30 minutes after application. More importantly, these compounds can be a main cause of skin allergy.
Many people say their eyes sting and water all day, leaving them red, whenever they apply sunscreen.
The cause of that stinging, redness, itching and burning is specific chemical filters.
The ingredients that most often cause allergy are these.
Oxybenzone (benzophenone-3): a representative cause of eye stinging and skin irritation, with concerns about cell toxicity — to be avoided by anyone with sensitive skin.
Avobenzone: blocks UVA well but is unstable in light, and as it breaks down it readily causes irritation and stinging.
Octinoxate: spreads well but can cause contact dermatitis or allergy.
So those with allergic tendencies like mine, or who have had severe stinging from sunscreen, should check the ingredient list and avoid chemical filters.
I recommend mineral sunscreen readily to the following.
Those who have recently had laser or peel treatment (the skin barrier is weakened and vulnerable to chemical irritation)
Children and infants (this is why products made for children are mostly mineral)
Those who drive often or need to go outdoors immediately (protection begins on application)
Photographing the skin with a diagnostic device before and after applying sunscreen, the area covered with mineral filter appears completely black on the UV image — UV light fully blocked.
Seeing it visually brings home how strongly sunscreen protects the skin.
If you need to buy something quickly while travelling, choosing one marked Mineral Sunscreen or Kids is safe.
Knowing clearly what the numbers mean helps you avoid excessive chemical exposure day to day.
UVB burns the skin surface and reddens cells, and is closely linked to skin cancer.
The SPF figure indicates, in theory, how much longer you can stay in the sun than with nothing applied.
SPF 30: blocks about 97%
SPF 50: blocks about 98%
SPF 100: blocks about 99%
The increase in protection as the number rises is smaller than people assume.
For everyday life, SPF 30 or above gives sufficient protection.
UVA penetrates deep into the skin, causing melasma and freckles and destroying collagen to produce photo-ageing.
For those who want to protect clear skin and prevent ageing, this figure matters more than SPF.
PA+ (low) / PA++ (moderate) / PA+++ (high) / PA++++ (very high)
For everyday life in a city, choosing PA+++ or above is the medical standard for keeping skin smooth.
Medically, reapplying every two to three hours is far more effective than applying a high-factor product once.
Outdoors, sunscreen is easily removed by sweat and oil.
Reapplying repeatedly outdoors with unwashed hands can be inconvenient.
In that case, blocking the sunlight physically with a hat, parasol, sunglasses and long sleeves is the most reliable and safest protection I can recommend.
This summer, please consider your skin type and the ingredients carefully and protect your skin with the right sun care. Thank you.
Our medical team will advise you based on your skin condition.
