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Cover Up - Hot tips on sun safety

Cover Up - Hot tips on sun safety

Adeline Tay

While there have been many reports on the benefits of sun exposure and the harmful effects from too much of it, little has been discussed about the skin's allergy to the sun. We tell you how not to get sore under the sun.

Skin can sometimes react abnormally to the sun. This results in a rash, exaggerated sunburn, painful swelling, hives or even blistering. Such a photosensitive reaction can occur in less than half an hour, or it can take up to 48 to 72 hours after exposure to manifest.

What brings it on
20000322-square.jpg (12013 bytes)Sunlight contains both ordinary visible light and shorter invisible light rays known as ultraviolet radiation (UV). This is in turn divided into UVB (shorter wavelength rays that burn and tan) and UVA (longer wavelength rays that tan). Patients can be sensitive to one kind of sunlight, that is, only to UVB or UVA or visible light, or to a wider range of radiation. The most common photosensitivity is to UVA.

While sunlight on its own can aggravate the skin, the ingestion of certain medications or contact with certain chemicals can also bring about sensitivity to the sun.

Drugs are another cause of photosensitivity. Those that are known to cause sun sensitivity include acne medications such as tretinoin (Retin-A), diuretics such as hydrochlorothiazide (Hydrodiuril), tranquilisers such as chlorpromazine (Thorazine), oral antibiotics such as tetracyclines, sulfa drugs, hypoglycemics such as chlorpropamide (Diabinese), non-steroidal anti-inflammatories such as Naproxen, and antihistamines.

Chemicals, fragrances or plant materials in contact with the skin can also produce photosensitive reactions. Known examples are coal tars in some medicated soaps and shampoos, bergamot oil in certain perfumes, toilet soaps, lemons and limes.

Patients may not associate their skin problem with sunlight. It is not always the sun that is responsible; very sensitive individuals can even be affected by fluorescent lamps indoors.

Sometimes, the cause is unknown, as in the case of a polymorphic light eruption. This reaction is more common in Europe and the United States, often developing on the first sunny outing or during a winter holiday to a sunny destination.

The most serious case of photosensitivity is chronic actinic sensitivity. "When this happens, patients need to be admitted to the hospital and put in darkness," says Dr Colin Kwok, a dermatologist with the National Skin Centre. "It normally occurs in the elderly but is not a common disorder," he adds. About five percent of the patients seen at the Centre for skin problems have been diagnosed with this disorder.

The good news is, relatively few people here ever become photosensitive. This could be due to the hardening of skin caused by the abundant sunshine here, explains Dr Kwok. The risk is higher for those who only have intermittent exposure to the sun, those who have light-coloured skin and those who tend to burn instead of tan.

Tests for photosensitivity
Phototests or photopatch tests can confirm photosensitivity. In a phototest, artificial light from various different sources is shone on small areas of the skin to see whether the rash can be reproduced, or if sunburn occurs more easily than expected.

Photopatch tests are used to check if sun sensitivity is brought about by contact with certain items. Adhesive patches containing known photosensitising materials are applied to the upper back, removed after two days, and light is shone on the area. The reaction is observed two days later.

Protecting your skin
There are simple ways of protecting your skin. For starters, known photosensitisers should be avoided
  • Avoid sun exposure. As the sun's rays strike the earth more directly and increase UV penetration during the middle part of the day, outdoor activities between the peak hours of 10.00am and 4.00pm should be minimised.
Reflective surfaces, such as sand and concrete, reflect UV rays and can nearly double the amount that gets to the skin. In fact, a person's UV exposure is significant even when sitting under an umbrella at the beach. An overcast sky does not reduce UV substantially and provides only minimal photoprotection. Protect yourself in the car and house too, as the longer UVA wavelength can pass through window glass.

  • Cover up. When sun exposure is unavoidable, wear shirts with a high collar and long sleeves, trousers or a long skirt, socks and shoes. Clothes should be of tightly woven fabric to reduce the penetration of UV radiation to the skin. The thickness of the clothing is more important than the colour. Make use of umbrellas and hats as well.
  • Use sunscreens. Sunscreens protect by scattering or absorbing UV light. Sunblocks reflect UV, visible and infrared rays, and achieve high sun protection factors (SPF) when used with chemical absorbers.
Chemical sunscreens, on the other hand, are wavelength selective with a specific absorption spectrum. They can block out more than 99 percent of UVB and 90% of UVA if applied correctly.

For effective protection, use a sunscreen with an SPF of at least 15. Apply the sunscreen liberally first thing in the morning to all uncovered skin. Protect your lips with dark coloured lipstick or a UV-absorbing lipsalve. If you are outdoors, do reapply your sunscreen frequently even if the label claims it is sweat proof.

Unfortunately, photosensitive patients often find it difficult to find a sunscreen they can tolerate. Sometimes this is because of generally sensitive skin; other times this is due to an allergic reaction to one of its components, which may be a fragrance, a preservative or a sunscreen chemical.

If changing the brand doesn't solve the problem, ask your dermatologist for advice. He may organise patch tests. Be careful to test a new product on a small area for a day or two before applying it widely.

  • Other measures. For the most severely light-sensitive patients, normal activities may be severely curtailed. Some find night work and sleep during the day while others put up with the rash. Nearly always, medications in the form of ointments or tablets can help to a variable extent.
Even if a person is not photosensitive, it is wise to be careful about sun exposure. By taking appropriate precautions and using common sense, individuals can achieve photoprotection.

  1. Turkington, Carol A. & Dover, Jeffrey, S., M.D. (1998), Skin Deep. Facts on File, Inc. New York, USA.
  2. Dr Tham Siew Nee, Dr Tay Yong Kwang & Dr Khoo Shih Wee, Lawrence (1995), Study on the epidemiology of photodermatosis seen at the National Skin Centre, www.nsc.gov.sg
  3. MacKie, Rona M. (1992), Healthy Skin: The Facts. Oxford University Press. USA.
  4. Photosensitivity, www.dermnet.org.nz

Date reviewed: 11 May 2005

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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