What is a Sunscreen?
Sunscreen is a topical (to apply on the skin) product that protects the skin against harmful effects of the sun.
How Can the Sun be Dangerous?
The sun, besides emitting visible sunlight, also emits non-visible ultraviolet (UV) rays.
UV-B rays may cause sunburns and skin cancer (through a damage of DNA in the skin cells). New studies suggest that UV-A rays may also cause skin cancer (1). UV-A exposure may result in photo-aging: skin wrinkling, age spots (hyper-pigmentation), freckling, visible capillaries, and lost of skin elasticity (through the breakdown of connective tissue in the skin) (2).
Eye disorders include: corneal growths, cataract, and iris melanoma (2).
Skin sensitivity with an unusually strong reaction to the sun is known as photosensitivity. Severe sunburn may appear in some individuals with systemic lupus erythematosus, dermatomyositis, psoriasis, several hours after contact with some fragrances or vegetables (3), or after taking tetracycline, anti-rheumatic ibuprofen, diuretic furosemide, and so on (4).
Does Suntan Protects Against Skin Cancer?
Suntan does not protect against skin cancer, and not completely even against sunburn (4).
How Does Sunscreen Work?
Substances in sunscreen either absorb or reflect UV rays, thus preventing them from reaching the skin.
The following substances are FDA (American Federal Drug Administration) approved as active sunscreen ingredients (4):
- UVB filters (absorbers): p-aminobenzoic acid (PABA), octinoxate, ensulizole acid, padimate O, trolamine salicylate
- UVA filters (absorbers): avobenzone, ecamsule (Mexoryl SX)
- UVA + UVB absorbers: oxybenzone, dyoxybenzone
- UVA + UVB reflectors: titanium dioxide and zinc oxide
Antioxidants in sunscreen neutralize free radicals triggered by UV rays. Vitamin C (improves skin healing) and E (somewhat protects against DNA damage) are also often added.
Preservatives and scents may be present or not.
Base substance in the sunscreen may be water, alcohol, oil or powder.
Is Sunscreen Proven as Effective Against Cancer?
This is hard to confirm by an experiment. Some studies have suggested that sunscreen protects against actinic (solar) keratoses and squamous cell carcinoma (4). No sunscreen can be considered 100 % protective against skin cancer, though. Other sun-protective measures, as avoiding sun, wearing protecting clothes and UV-protecting sunglasses should be considered.
Types of Sunscreens
Broad-spectrum sunscreens (most of them available today) protect against both UVB and UVA rays, but they still do not provide 100% protection.
Physical and Chemical Sunscreens
Physical sunscreens, containing zinc oxide or titanium oxide, reflect UV rays. Chemical sunscreens contain substances, like PABA or oxybenzone, that absorb UV rays. Many sunscreens are combined physical + chemical sunscreens.
Organic, Natural and Biodegradable Sunscreens
Producers of “organic” or “natural” sunscreens claim that their products do not contain any ‘chemicals’, what usually means they do not contain oxybenzone and other UV absorbers (known as chemical sunscreens), but they do contain zinc oxide, iron oxide, titanium oxide, silica or talcum that reflect UV rays (known as physical sunscreens). It is true that zinc oxide or titanium oxide do not commonly cause side effects. But there may be other organic substances in an ‘organic’ sunscreen that may irritate your skin, so find out by yourself what is appropriate for you.
“Biodegradable” sunscreensare becoming popular, since it was discovered that non-degradable sunscreens may destroy algae on coral reefs.
Water Resistant Sunscreens
“Water resistant” sunscreens should retain its SPF after 40 minutes of immersion in water, and “very water resistant” after 80 minutes (4). Claims about water resistance are usually found on “sport” sunscreens. They are thick and not convenient for everyday use. No sunscreen is “waterproof”, since every sunscreen is washed off the skin after some time.
Sunscreens for Oily, Dry or Sensitive Skin
For oily skin, oil-free (water-based or powdered) sunscreens are convenient.
For dry skin, sunscreen with a moisturizer, or oily sunscreen may be appropriate; alcohol-based ones should be avoided.
For sensitive skin, alcohol-free, fragrances-free (non scented) and purely physical sunscreens (containing only zinc oxide or titanium oxide as an active ingredient) are appropriate. Any of these sunscreens may still irritate your skin, so you have to find appropriate one yourself.
Some Misleading Terms
No “sunblock” sunscreen can completely block UV rays, no “all day” sunscreen protects skin for 24 hours, no “waterproof” sunscreen is completely waterproof after several hours after applying, rare “natural” or “organic” sunscreens contain only natural or organic components, and no sunscreen is completely “safe”.
Forms of Sunscreen
Lotions and sprays are not messy, so they are convenient for the scalp with scarce hair or hairy skin.
Creams and gels do not flow, so they are convenient for the face.
Sticks are thick, and thus convenient for the eyelids or lips (lip-screen).
Powders are convenient for oily skin.
A sunscreen with moisturizer is convenient for dry skin.
Sun Protecting Factor (SPF)
The sun protecting factor (SPF) tells what part of UVB rays will break through the sunscreen (currently there is no measure for UVA rays). SPF 3 will allow 1/3 of UVB-rays to penetrate through the sunscreen, SPF 15 will allow 1/15 of UVB-rays (~7 %), SPF 30 1/30 (~3%), and SPF 50 1/50 (2%). There is no sunscreen that can 100% protect the skin against the harmful effects of UV-rays.
Current FDA approved SPF range is from 2 to 30+ (5), but SPF designated 50+ can be found on the market.
The use of sunscreens with the sun protecting factor (SPF) at least 15 is now recommended.
Is Last Year Sunscreen Still OK?
Most of sunscreens have their shelf life of at least 2 years. Check the expiration date.
Who Should Use a Sunscreen?
Anyone after 6 months of age, exposed to intense sun, even if only for 10 minutes, should use a sunscreen. Children, outdoor workers, drivers and all who are repeatedly exposed to the ‘normal’ sun for long periods, should also use sunscreens. Read about skin cancer prevention.
Who Should Not Use a Sunscreen?
Sunscreens should not be used:
- In infants before 6 months of age
- By persons with an allergic reaction to particular sunscreen
- In intense sunburn with blisters
- In oozing skin infections
- On skin areas near open wounds
How to Apply a Sunscreen?
Sunscreen should be applied 30 minutes before sun exposure, and then every two ours, or immediately after swimming or heavy sweating. It should be applied generously and evenly, and rubbed well into the skin. All parts of the sun-exposed skin should be covered, including ears, the skin behind ears, and the scalp with scarce hair.
Use a lip-screen for lips. Skin cancer often develops on the lip.
Applying sunscreen on the eyelids and around the eye is not recommended since it may irritate the skin. Use big sunglasses with 100% UV filter instead.
If different ointments are applied on the skin, medicated ointment should be applied first, then moisturizer, and then sunscreen. Moisturizer can dilute the sunscreen thus reducing its SPF, so products that are moisturizers and sunscreens at the same time are recommended.
How to Use Sunscreens in Young Children?
Infants before 6 months of age should be protected from a sun exposure as much as possible, and sunscreens should not be used. Do not use baby oils before going out, since they may make skin vulnerable to sunburn.
Do Sunscreens have Side Effects?
You may be sensitive to some sunscreens. A day before sun exposure put some sunscreen on the inner side of the wrist. If a redness appears, it means you are sensitive or allergic to that particular sunscreen product and you should avoid it. You may have a skin patch test to determine to a which exact substance you are sensitive.
So far, there is no proof that any sunscreen would cause cancer (1).
Alcohol based sunscreens my have a drying effect.
To the date there is no agreement, if sunscreens prevent vitamin D production in the skin. In any case, persons with vitamin D deficiency should not avoid sunscreens, since vitamin D can be obtained by food, but sunscreens often can not be substituted with another protection (4).
Does a Safe Sunscreen Exists?
No sunscreen can 100% protect you against a sunburn or cancer. There is also no sunscreen that can be considered as safe in the sense it will not cause any side effect or allergic reaction.
What About Home Remedies?
Various herbal components are advertised as sunscreens. In most cases, sun protective factor of these substances is not known, so it is not reliable to use them alone as sunscreens.
So, Which Sunscreen to Use?
Characteristics of good sunscreen:
- SPF at least 15
- Broad-spectrum (UVA + UVB protection)
- Not irritating your skin (check ingredients, use intuition)
- Feels comfortable (use appropriate form of sunscreen, read above)
- UV-A and skin cancer (healthlink.mcw.edu)
- Damaging effect of UV rays on the skin (umm.edu)
- Photosensitivity – causes and related conditions (dermnetnz.org)
- No side effects of sunscreens were confirmed so far (skincancer.org)
- FDA approved SPF range is 2-30+ (fda.gov)