Exposure to sunlight can have both beneficial and harmful effect on the human body. The sun emits rays of electromagnetic energy which has both good and bad effects on human skin. Depending upon the length and frequency of exposure, the intensity of the sunlight and the sensitivity of the individual concerned the rays has different effects.
The wavelengths of solar electromagnetic waves are extremely small and are measured in nanometres. The solar spectrum extends from rays of approximately, wavelength 285 to 100000 nm, within which range visible light occupies a band from 390 to 760 nm. Solar rays of wavelength 390 to 285 nm occupy part of the ultraviolet region of the electromagnetic spectrum, while rays of wavelength from 760 to 100000 nm are those of infra-red radiation.
The most obvious effect of exposure to the rays of the sun is first of all erythema(reddening) of the skin, followed by the formation of tan. The intensity of erythema (reddening) produced on the skin following exposure to sunlight depends on the amount of UV energy absorbed by the skin.
Radiation within the band of wavelength 285 to 420 nm is ultra-violet light (UVL) of the kind which results in sunburn and tanning of the skin, and is divided into two types, according to its effect on the skin:
- Ultraviolet light B (UVB), of wavelength 285 to 320 nm, causes sunburn, and prolonged tanning of the skin due to sunburn.
- Ultraviolet light A (UVA), of wavelength 320 to 420 nm, imparts a direct, though relatively short-lived tan to the skin. It can cause premature ageing of the skin.
- Erythema usually starts to develop after a latent period of 2-3 hours and reaches its maximum intensity within 10 to 24 hours after exposure.
Beneficial Effect Of Sunlight
Moderate exposure of the human body to sun rays results, psychologically and physiologically, in a general sense of fitness, peace of mind and general well-being. Also, it has certain definite beneficial effects on human health. It stimulates blood circulation, increases the formation of haemoglobin and may also promote a reduction in blood pressure. Furthermore, it plays a vital part in the prevention and treatment of rickets by the production of vitamin D, which enhances the absorption of calcium from the intestine.
It has been used in the treatment of certain types of tuberculosis, such as the tuberculosis of glands and bones, and the treatment of certain skin diseases such as psoriasis. It is also believed to exert a beneficial influence on the autonomous nervous system and to reduce the susceptibility of individual to various infections. Finally, by producing melanin (a broad term for natural pigments found in most organisms) and causing thickening of the skin, it plays an essential role in the formation of the body’s natural protective mechanism against sunburn.
Adverse Effect Of Sunlight
The tanning ability of an individual is genetically predetermined and depends on his capacity to produce melanin pigment within the melanocytes(melanin forming cells). There are three types of tanning responses:
- Immediate tanning;
- Delayed tanning;
- True tanning, also referred to as melanogenesis.
1) Immediate tanning – It is stimulated by energy between 300 nm and 660 nm and its maximum efficacy lies between 340 nm and 360 nm. It entails the immediate darkening of unoxidized melanin granules present in the epidermal layer of the skin, near its surface. It reaches a maximum about one hour after exposure to radiation and begins to fade within 2-3 hours after exposure.
2) Delayed tanning- It involves the oxidation of melanin granules present in the basal cell layer of the epidermis and their migration towards the surface of the skin. It may start as early as one hour after exposure, reaches a peak after some ten hours and then fades rapidly after 100 to 200 hours following exposure.
3) True tanning- It starts about two days after exposure and reaches a maximum of about two to three weeks later.
The short-term effect, as far as the skin is concerned, is temporary damage of the epidermis, manifesting itself is the known symptoms of sunburn. These may range in severity from slight erythema to painful burns and blistering accompanied in more severe cases, when large amounts of the skin have been affected, by shivering, fever, and nausea.
The symptoms of the sunburns are the direct result of damage or destruction of cells in the prickle cell layer of the skin, possibly through denaturing of its protein constituents. Histamine-like substance releases by the damaged cells are responsible for the dilation of blood vessels and erythema. They also cause swelling of the skin (oedema) and stimulate the basal cells of the skin to proliferation.
Four degrees of sunburn:
- Minimal Perceptive Erythema – a slight, but discernible red or pink colouration of the skin, produced with 20 minutes of continuous exposure to sunlight.
- Vivid Erythema– a bright red colouration of the skin, not accompanied by any pain, produced with 50 minutes of continuous exposure to sunlight.
- Painful Burn– characterized by both vivid erythema and pain ranging from mild to intense, produce with 100 minutes of continuous exposure to sunlight.
- Blistering Burn– characterized by an extremely high level of pain accompanied by vivid erythema and possibly systematic symptoms with blistering and peeling, produced with 200 minutes of continuous exposure to sunlight.
Sunburn does not leave any scars. A slight burn protected from further exposure to sunlight will disappear within 24- 36 hours. More severe burns will generally heal within 4-8 days. As the inflammation subsides it will be followed by peeling of the skin.
Effects due to Chronic Exposure
Chronic exposure to intense sunlight, to which sailors, farmers, and construction workers are entails more serious hazards such as, for example, the development of skin cancer. It may also produce degenerative changes in the connective tissue if the corium, and the result is the so-called premature ageing of the skin. This is evidenced by the thickening of the skin, the loss of natural elasticity and the appearance of wrinkles, all resulting from the loss of the skin’s water-binding capacity.
How To Protect The Skin From The Harmful Effect Of Sunlight?
The skin may be protected by the harmful effect of sunlight by the application of a suitable sunscreen preparation which is effective in reducing, by absorption, the levels of UVA and UVB reaching the skin. Sunscreen preparations are sold in a number of different forms, which include lotions, gels, creams, and oils. These products contain a UV light filter and are assigned a sun protection factor (SPF) corresponding to the degree of protection it confers upon the skin following a normal application. The more sensitive the skin is to sunlight, the higher must be the value of the SPF of the product used for protection of the skin.
Clothing is the most basic form of protection against the sun. Colors like white, yellow, beige and other light shades keep the body cool because they reflect most of the sun’s rays back into the atmosphere. Dark fabrics, on the other hand, tend to absorb these rays and trap their heat and feel even hotter. Wear clothes that keep the skin covered. Long pants and long sleeved shirts cover the skin and avoid tanning. Cotton is the most commonly used fabric during summer as it is lightweight and breathable.
Tan Removing Agents
Some substance used on a regular basis help to remove or reduce tanning. These substances are generally present in the kitchen stuff that we need daily. Some of them are:
Lemon is often used to remove scars on the face. But, it can also be used to reduce tan without making the skin dry. Lemon contains vitamin C which is a great tan removal agent. The citric acid present in lemon helps not only to remove tan but also helps in the removal of acne and dark spots. The acid present in the lemon juice act as skin lightening agents. Rub a slice of lemon on the tanned region and leave it for a few minutes then wipe it off. Doing this you will definitely get positive results. You can also use the mixture of lemon and curd or lemon juice and cucumber for detaining.
Turmeric contains anti-aging and skin lightening properties that protect the skin against harmful UV rays of the sun. Make a thin paste of turmeric powder with milk and apply it on the affected area. Leave it to dry and rinse off with water.
3. Gram Flour-
Gram flour (besan powder) is very useful in treating tan. It also removes dead cells and gives a healthy, glowing skin. Simple gram flour paste made with either water or rose water proves to be quite effective in removing tan. Besan mixed with curd and pinch of turmeric is also very effective. You just need to apply the paste and wait for it to dry. After drying rinse your face with water.
It is one of the best remedies to remove tan. Apply curd for few minutes and massage gently. Wash it off after 5 minutes. If your skin is dry make a blend of honey and curd. Curd used with tomato is also very effective. Mash the tomato and add some amount of curd in it and mix the blend well. Apply on the affected areas and wash it off with water after 20 minutes.
Raw potato juice is the best natural remedy for tanned skin. It acts as a natural bleaching agent and counters the effect of tanning. Grate a potato and squeeze out the juice and apply on the affected areas. Rinse it off after 10 minutes.
If you are one of those who don’t believe in artificial products then given below are some techniques to make home-made sunscreen
- Mix milk and honey in equal quantity properly. Apply it with the help of cotton swab. Wash with cold water after 20 min.
- Mix equal quantity of sesame oil with aloe vera gel. Stir the mixture properly and store it in a container. Applying it before going out in the sun will act as a sunscreen.
- Take a small amount of coconut oil and mix it with two tablespoons green tea powder. Heat the mixture for 10 minutes in a double boiler ( do not heat directly as it contains coconut oil). Stir the mixture properly. followed by mixing it with 2 vitamin E capsules in the filtrate. Add 2 tablespoon of aloe vera gel and mix it properly until it forms a smooth cream-like structure. Apply before sunbathing will act as suntan lotion.
- Mix 1 tablespoon of coconut oil, 1 tablespoon of shea butter and a small amount of beeswax. Heat it in a double boiler until it melts. Add 1 tablespoon of zinc oxide powder and 1 tablespoon of aloe vera gel. Stir the blend properly until it mixes properly. Store in an airtight container. It will surely act as a sun blocker giving protection to your skin against sun rays.
- Mix 3 tablespoon of aloe vera gel with 1-2 tablespoon of cucumber gel and half tablespoon of coconut oil. Mix the blend properly and add 1 tablespoon of zinc oxide powder. Stir the blend properly and store in an airtight container. Apply it before going out in the sun will definitely give you positive results.
Above explained sunscreens are all can be prepared with the ingredients available at home on a daily basis. However, there are various products available in the market and in which a large number of sun screening agents are used. Let’s brief about the various chemicals which act as sun screening agents and their various advantages and disadvantages.
Chemicals Used In Various Artificial Sunscreen
The astronomical variety of Sunscreen available in the market has different chemicals and sun screening agents which have both good and bad effect on the skin. The sun screening agents present contains titanium dioxide (TiO2), kaolin, talc, zinc oxide (ZnO), calcium carbonate, and magnesium oxide. There are also some newer chemical compounds, such as bemotrizinol, avobenzone, bisoctizole, benzophenone-3 (BZ-3, oxybenzone), and octocrylene, these are broad-spectrum agents and are effective against a broad range of the solar spectrum. Classification of sun screening agent is shown in the figure below. Commercial preparations available in the market include a combination of these agents to cover a wide range of UV rays.
Ideally, sunscreen agents should be safe, chemically inert, nonirritating, nontoxic, photostable, and able to provide complete protection to the skin against damage that solar radiation does. But as it is believed ideal things do not exist and to the same sunscreens sometimes have side effects.
Sunscreen agents should be formulated in a cosmetically acceptable form and ingredients should remain on the upper layers of the skin even after sweating and swimming. Sunscreens should not only protect the skin from the sun but also minimize the cumulative health hazards from sun damage caused over time.
Hazards Of Sunscreening Agents On Skin
Although considered safe, sun screening agents are not free from adverse effects. Sensitivity, though rare, can occur in the form of photoallergic reactions, including contact dermatitis. Vitamin A, which is a widely used compound in cosmetics and sunscreens (as an antioxidant against the aging effects of UV radiation), is considered to increase the rate of the development of skin tumors and lesions. Exacerbation(the process of making) of acne and rosacea(enlargement of blood vessels) can also occur with the use of sunscreen agents that contain physical blockers, such as ZnO and TiO2, that are greasy and have large particle sizes, thereby blocking skin pores.
Precautions To Be Taken While Using Sunscreen
Sunscreen products are available with and without a doctor’s prescription. If rash or irritation develops, stop using the sunscreen and check with your doctor. In addition to using sunscreen agents, it is advisable to minimize exposure to the sun from 10 a.m. to 2 p.m. (11 a.m. to 3 p.m. daylight savings time) when the sun is at its strongest. Take extra precautions also on cloudy or overcast days and around reflective surfaces such as concrete, sand, snow, or water, since these surfaces can reflect the sun’s damaging rays. Wear protective clothing including a hat, long-sleeved shirt, and long pants. Sunglasses should be worn to avoid sun damage to the eyes (cataract formation). Avoid sunlamps and tanning parlors because they include a procedure in which light is used that damage the skin and eyes as it has the same effect as direct sunlight. The following are skin types (complexions) and the appropriate sunscreen agent that should be used:
- Very fair; always burns easily; rarely tans—Use SPF 20 to 30.
- Fair; always burns easily; tans minimally—Use SPF 12 to 20.
- Light; burns moderately; tans gradually (light brown)—Use SPF 8 to 12.
- Medium; burns minimally; always tans well (moderate brown)—Use SPF 4 to 8.
- Dark; rarely burns; tans profusely (dark brown)—Use SPF 2 to 4.
Factors To Be Considered Before Using Sunscreen
Sunscreen agents we use are for external use only. These products usually come with patient directions. Careful reading is advised before using any product. In choosing any sunscreen product, the following points should be considered for better effectiveness.
- Age—Do not use sunscreen agents on infants younger than 6 months of age. For children 6 months of age and older, use a lotion form of sunscreen with broad-spectrum and SPF of 15 or higher. Avoid using alcohol-based sunscreen products for this age group.
- Site of application—For ear and nose, use a physical sunscreen agent. For the lips, use a gel-based lip sunscreen or lip balm
- Skin condition—If your skin is dry, use a cream or lotion form of sunscreen agent. If your skin is oily, use an alcohol or gel-based sunscreen. Avoid using alcohol-based sunscreens on eczematous or inflamed skin.
Sunscreen For Asian Skin
Asian skin, which is darker in color, rarely burns and is more prone to rapid tanning. Asian skin is comparatively smoother, with a slight yellowish tinge and is more prone to pigmentation. Presence of protein melanin in the skin of Asians differentiates it from the skin of Caucasians. It has been observed that melanin equally filters all wavelengths of light, thereby receiving five times less UV radiation. This protein provides photoprotection to a certain extent, minimizing phototoxicity and making the skin less vulnerable to acute and chronic phototoxic effects.
Nevertheless, this population shows the effects of photodamage in terms of pigmentation, wrinkling, and sunburn. The formation of freckles in the Asian population is encountered much less frequently. However, overexposure to sunlight can cause photodamaging effects, including skin cancers. Hence, it is advisable for Asians to use sunscreen agents regularly as a preventive measure just as it is in other parts of the world. However, since Asian skin is more prone to hypersensitivity reactions, cosmetic products should be used with care.
Hence, the use of sun screening agents is beneficial in minimizing the occurrence of skin cancers in people with fair skin. However, the same effect on Asian skin is debatable, as this skin type is considered to be resistant to skin cancers. Sunscreen use is advisable in young adults to prevent and minimize other photodamaging effects. Natural homemade remedies, on the other side, can be used without any adverse effect but their shelf life is limited to a very small extent ( not more than 2-3 weeks). As we see that sunbathing has a very adverse and toxic effect it is important to use sunscreen, either natural, homemade or the products which are present in the market.