"I applied sunscreen every day, but dark spots appeared" Turns out there was an issue with 'basic skincare'

Applying too much basic skincare products such as lotion and toner before sunscreen can reduce the effectiveness of the sunscreen. Dr. Seo Dong-hye of Beautiful Nation Dermatology said, "Sunscreen needs to penetrate the skin, but applying too many basic skincare products before sunscreen can diminish its performance," and added, "There is also a higher chance of unknowingly wiping it off, so it's better to lightly apply just one lotion and then put on sunscreen."

Particularly, extra caution should be exercised when using organic UV filters. There are mainly two types of sunscreens: ▲chemical filters called organic UV filters and ▲physical filters called inorganic UV filters. Organic UV filters contain chemical ingredients such as para-aminobenzoic acid, ethylhexyl methoxycinnamate, avobenzone, and oxybenzone, which are absorbed into the skin and react with UV rays instead of the skin, converting and releasing them as infrared rays with low energy that are harmless to the human body. Inorganic UV filters, such as zinc oxide and titanium dioxide, form a barrier on the skin with inorganic chemicals, reflecting and scattering UV rays. When organic UV filters are mixed with other skincare products on the skin, the blocking ingredients may be diluted or undergo chemical reactions with other components.

If you have applied a lot of basic skincare products, it is better to wait until the applied products are fully absorbed into the skin before applying more. Director Seo Dong-hye said, "It's okay to apply sunscreen and makeup, but in this case, the effectiveness of inorganic UV filters in sunscreens may be slightly reduced," and added, "Since the ingredients in UV protection products block different wavelengths of ultraviolet light, layering UV protection products, such as applying a cushion with UV blocking effects over sunscreen, can enhance UV protection without irritating the skin."

In addition to applying sunscreen on a thin base layer, it is important to apply a thick layer of products with appropriate SPF and PA ratings 15 to 30 minutes before outdoor activities to enhance protection. Since sweat and other factors can remove the sunscreen during outdoor activities, it is advisable to reapply every two hours.

If all these efforts still do not provide significant UV protection, you should check the product's 'expiration date.' Sunscreens also have expiration dates. Before opening, they usually last 2 to 3 years; after opening, about 1 year. As the expiration date approaches, the ingredients in the sunscreen may decompose or deteriorate, gradually losing their protective effect. Even if the formulation separates, the UV protection may decrease. Sometimes, it can cause skin troubles such as acne, so it is advisable not to use sunscreens past their expiration date. Inorganic UV filters generally have a longer shelf life than organic UV filters. Zinc oxide and titanium dioxide contained in inorganic sunscreens are stable ingredients and do not change even when exposed to light. The ingredients in organic sunscreens are relatively more vulnerable to oxidation.

Meanwhile, SPF indicates the level of protection against ultraviolet B rays, and the PA index indicates the level of protection against ultraviolet A rays. Ultraviolet B can cause sunburn, while ultraviolet A can lead to photoaging and skin cancer. The number following SPF represents how much it reduces the amount of UV rays reaching the skin. SPF 30 absorbs about 96.67% of UVB rays, and SPF 60 about 98.33%. Instead of a number, a plus sign '+' is attached after PA. The more '+' signs, the higher the UV protection level. People who do not go outdoors often should choose products with around SPF 10 and PA+. For light outdoor activities, SPF 10-30 and PA++ products are sufficient. For long outdoor activities such as hiking, it is recommended to use SPF 30-50 and PA++++ products.

Pigmentation symptoms such as melasma and freckles are difficult to treat once they occur, so prevention is most important. Director Seo Dong-hye said, "Applying sunscreen properly is important, but sunscreen cannot block 100% of ultraviolet rays," and "If dark spots or melasma still develop despite proper application, efforts to reduce exposure to sunlight itself should be the premise." Since UV rays are strongest about two to three hours before and after noon, it is best to avoid going out during this time as much as possible. If you must go out, you can block UV rays with umbrellas, hats, and other protective gear.