- The minimum erythema dose, MED, which determines the time it takes for erythema to appear during sun exposure, is 15 minutes.
- The SPF index only applies to protection against UVB radiation.
- SPF protection should be matched to your skin phototype.
- There are two types of sunscreens - chemical and mineral. They can be combined in one cosmetic formula.
- Apply sunscreen at a rate of 2 mg/cm2 of skin.
- The use of sunscreen creams does not block the synthesis of vitamin D in the body.
During the holidays, we dream of a beautiful tan. Effectively bronzed skin actually looks good, but the way to achieve it may have dangerous consequences for your health. UV radiation is no joke . In addition to a nice tan, it can give us erythema, sunburn, discoloration and other symptoms of photoaging , and in the worst scenarios - cancer . How to expose your skin to the sun wisely? Safe sunbathing will be guaranteed by appropriate SPF protection .
What is SPF really?
SPF , from the English Sun Protection Factor , is an indicator of the degree of skin protection against sun rays, determining how many times longer the skin is protected against UVB compared to unprotected skin before erythema occurs . Usually, in the case of unprotected skin, erythema appears after about 15 minutes of exposure to the sun (minimum erythema dose, MED) [1] .
The higher the SPF factor, the safer the skin stays. For example, SPF 30 increases the length of epidermis protection by 30 times, so it will extend to 450 minutes (30 x 15 minutes, in theory). Of course, this does not mean exposing your body to the sun for such a long time. No sunscreen guarantees 100% protection against UV rays. Also keep in mind that during the day the cosmetic simply rubs off and is washed away with sweat . Therefore, it requires reapplication .
Although the SPF index only applies to protection against UVB radiation , according to the recommendations of the European Commission, the degree of protection of sunscreen cosmetics against UVA should be at least 1/3 of the protection against UVB [2] . Some manufacturers indicate the level of protection against UVA rays with IPD, PPD or PA factors with pluses (the more pluses, the higher the protection).
SPF protection should be matched to the skin phototype, which depends on the amount of melanin contained in the tissue. There are 6 types, but in our climate zone the first 4 predominate:
- phototype I – fair complexion, often with freckles, blond or red hair. The skin is extremely sensitive to the sun, if left unprotected it burns very quickly and tans with difficulty. In her case, SPF 50 and 50+ are recommended.
- phototype II – light complexion, usually without freckles, blond or dark blond hair. Such skin is also sensitive to the sun and burns quite quickly, but it tans gently. Creams with SPF 50 are recommended to protect it.
- phototype III – light brown complexion, rather without freckles, dark blond or light brown hair. Burns are less common and you tan quite easily. SPF 20 and 30 are recommended.
- phototype IV – dark complexion, no freckles, light or dark brown hair. It tans easily and rarely burns. Protection with an SPF of at least 15 is recommended.
Types of sunscreens
Sunscreens are a unique support in daily skin care. Yes, every day, because we should protect the epidermis 365 days a year, not only in summer. What filters are in sun creams? There are two types (they can be combined in one formula, intensifying SPF protection):
- physical (or mineral) filters – reflect and scatter UVA and UVB radiation . They act only on the surface of the epidermis, leaving a protective layer on it, and do not penetrate deep into the skin. They are photostable and do not cause irritations or allergies . Therefore, they are especially recommended for protecting sensitive, reactive and children's skin. Their flaw? They are more difficult to spread and may whiten the skin . They can also clog pores. The most commonly used mineral filters are titanium dioxide (INCI: Titanium Dioxide ) and zinc oxide (INCI: Zinc Oxide ) .
- chemical (organic) filters – they have a low molecular weight and penetrate deep into the skin . effectively absorb UVA and UVB rays . Creams containing them have a light consistency and do not leave any white marks . Disadvantage of chemical filters such as salicylates or benzophenones? Because they penetrate the skin and can have a stronger effect on it, they have an increased allergic potential [3] .
Natural filters, which are found, among others, in fats and plant extracts, have become very popular in recent years. For example, raspberry seed oil, shea butter, macadamia oil or extracts of green tea, milk thistle, aloe or red clover have sun protection properties. Many of them are a source of antioxidants. However, they should not constitute a stand-alone sun protection. They can only support physical and chemical filters.
Golden rules of tanning - SPF protection is not everything
Follow these rules if you care about healthy skin before you put a blanket on the grass or beach:
- Apply sunscreen thoroughly to all parts of the body , without exception. Also on the skin of the ears, eyelids and lips;
- try not to expose your body to the sun for a long time during its peak activity hours, i.e. between 11 a.m. and 3 p.m.;
- do not depilate just before you plan to sunbathe . Removing hair before exposure to the sun may increase the risk of irritation, photoallergy and even discoloration. It is best to depilate a few days before sunbathing, if possible;
- watch out for photosensitizing ingredients and substances, e.g. St. John's wort extract, parsley, purple coneflower, horsetail, calendula, celery, selected medications, as well as photosensitizing substances such as some essential oils (mainly citrus), AHA and BHA acids, retinol or retinoic acid;
- In addition to SPF protection, also follow a diet and care full of antioxidants that will protect the skin against excess free radicals. They support protection against the effects of the sun. These include vitamins A, C and E, flavonoids present in many vegetables and fruits, melatonin and catechins contained, for example, in green tea leaves [4] ;
- don't forget about sunglasses and a hat - they will protect your eyesight and hair against the negative effects of UV rays.
How to apply sunscreen to the skin?
Sunscreen should be applied in a really thick layer. As a guide, in the amount of 2 mg/cm 2 of skin . This means, on average, about 2 ml of cream at a time for the face and neck, and 30 ml for the body. Unfortunately, in practice we apply too little of the preparation, on average 0.5-1.0 mg/cm 2 , which is more than half as much [5] . It's time to change that!
Also remember to reapply the sunscreen , which should be done every 2 hours, and every time after going out of the water or sweating excessively and drying with a towel.
Remember this so that sunbathing in the summer is completely safe
Information that will help you sunbathe wisely. You don't have to give up the sun, but use it in moderation. Remember about SPF protection and the following tips.
1. The higher the SPF factor, the safer it is
We usually apply too thin a layer of sunscreen on the skin. Therefore, it is worth choosing cosmetics with a high SPF factor. A higher sun protection value means greater safety. SPF 50 filters radiation by 98%, and SFP 15 - only by 93%.
2. SPF protection blocks the synthesis of vitamin D? MYTH!
The sun's rays provide, apart from a beautiful tan, several benefits. They help the body synthesize vitamin D, which is responsible, among other things, for the proper functioning of the calcium and phosphorus metabolism, and therefore indirectly for the health of bones and teeth. Yes, you can supplement it, but the sun has the greatest impact on its production - it only needs 15 minutes. But importantly, using sunscreen will not stop vitamin D synthesis - sunscreens never completely block UV rays .
3. Natural filters – yes, but only in combination with mineral and/or chemical ones
In the era of fashion for natural ingredients, some people treat increasingly popular natural filters, such as raspberry seed oil or carrot extract, as substitutes for mineral and chemical filters. Unfortunately, they expose themselves to the harmful effects of sunlight. Natural filters do not have the same degree of sun protection as mineral and chemical filters, and they are not as photostable . However, they can be an excellent support for protection against UV radiation, being a treasure trove of antioxidants.
4. SPF protection is never 100% safe
Sunscreens never block 100% of UV radiation . SPF 50 filters 98% of them, and the remaining 2% is enough to damage the skin structure during long-term exposure to the sun. At the same time, in addition to SPF protection, remember to wear appropriate clothing and accessories such as sunglasses, a hat, staying in the shade, reapplying sunscreen and limiting sunbathing during peak sun activity (11 a.m.-3 p.m.).
5. Replace your sunscreen every year
Sunscreen creams have a specific shelf life - usually 6 or 12 months . Additionally, over time they lose their protective properties . They are often stored incorrectly. What does it mean? Use them during one season and replace them every year .
6. Never add up SPF factors - it doesn't work like that
Combining different cosmetics containing sun filters does not add up their protection. SPF 20 plus SPF 30 DOES NOT GIVE SPF 50! The actual value of such care will be the highest index of cosmetics used. For example, you apply a foundation with SPF 15 and a cream with SPF 30 to your face, the level of protection is the same as the product with the highest SPF , i.e. in this example SPF 30.
7. Don't forget your sunglasses and hat
We've been rolling it out for a while now, but it's just as important as protecting yourself with sunscreen. A hat will protect you against possible heat stroke and protect part of your hair and scalp against UV rays, glasses protect your eyes against UV rays.
8. SPF filters are safe for health, but they are not neutral for the environment
Some sunscreens, both chemical and mineral, may negatively impact the environment of aquatic organisms [6] . Therefore, choose them consciously.
9. UV radiation also penetrates through glass
Yes, glass does not filter UVA radiation.
And one more thing - even if you use the highest sun protection, you will still get a tan. You will achieve a beautiful brown skin tone knowing that you are doing it in a safe way, slightly over time.
[1] Cosmetic chemistry, selected issues, edited by A. Sionkowska, Wydawnictwo Naukowe UMK, p.260
[2] Uzdrowska K, Górska-Ponikowska M. Sunscreen cosmetics as basic protection against photoaging. Aesth Cosmetol Med. 2022;11(6):225-230. https://doi.org./10.52336/acm.2022.029
[3] Cosmetic chemistry, selected issues, edited by A. Sionkowska, Wydawnictwo Naukowe UMK, pp. 250-261
[4] Uzdrowska K, Górska-Ponikowska M. Sunscreen cosmetics as basic protection against photoaging. Aesth Cosmetol Med. 2022;11(6):225-230. https://doi.org./10.52336/acm.2022.029
[5] Cosmetic chemistry, selected issues, edited by A. Sionkowska, Wydawnictwo Naukowe UMK, p.260
[6] Nial JW, A review of environmental contamination and potential health impacts on aquatic life from the active chemicals in sunscreen formulations, 2022, Australian Journal of Chemistry 75(4) 241-248 https://doi.org/10.1071/CH21236
