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Science Behind the Use of Sunscreen

Summer is not over yet. In fact, the way the weather has been acting up, we may end up with many more days of sunshine. May be we will get an early winter. But as long as the sun is shining, it continues to emit the harmful ultraviolet (UVR) rays. So, do not be in a hurry to put away your sunscreen lotion.

Chemical sunscreens were discovered in 1926. By 1928, the first commercial sunscreen, containing benzyl salicylate and benzyl cinnamate was marketed in the United States. Subsequent sunscreen evolution was primarily directed toward ultraviolet B (UVB) protection to lessen development of sunburn from overexposure to the sun.

Since 1960, the sunscreens contain para-amino-benzoic acid (PABA). It wasn’t until 1980, that sun protection factor (SPF) 15 became available in the market. PABA has several disadvantages and it has been replaced by PABA esters. These absorb well in the UVB range, are easier to formulate in nonalcoholic vehicles, and are less staining and less allergenic. Researchers continue to develop better sunscreens. Some scientists have determined that the viscous “red sweat” of the hippopotamus is an excellent, broad spectrum sunscreen. May be next time you see me, I will smell like a hippo.

Sunscreen should be efficient, water resistant and safe. It should spread easily, maximize skin adherence, should be non-stinging, non-staining, and inexpensive. Most popular sunscreens are available in creams and lotions (emulsions). Both are oil-in-water or water-in-oil preparations, although lotions spread more easily. Some sunscreens are oil based and greasy, some are in gel form but they tend to sting and irritate the skin. Sunscreens in the form of a stick are wax based but are difficult to apply in larger areas. Aerosols are wasteful with spray lost to the air. Increasingly, sunscreens are being incorporated into cosmetics, including lipsticks, and moisturizers.

The ability of a sunscreen to protect the skin from UVR-induced erythema is measured by the SPF. Erythema is defined as redness of the skin caused by dilatation and congestion of the capillaries, often a sign of inflammation or infection. In this case, the redness is from sunburn.

SPF 15 blocks 93 per cent of UVB. Some argue that SPF 15 is sufficient and that higher labeling claims are misleading and costly for consumers. But some studies have shown that higher SPF (SPF 30) sunscreens conferred better clinical and microscopic tissue benefits.

Most people who use sunscreens apply it at much lower concentrations than the 2 mg/cm2 at which they are tested. The resultant SPF is considerably reduced, typically to about 20 to 50 per cent of the labeled SPF for chemical sunscreens. It is important to remember that under-application, uneven application and delayed application of sunscreens result in unnecessary sun exposure and skin damage.

What the sunscreen does is to lessen the development of sunburn from overexposure to the sun by absorbing UVB sunrays. Recurrent sunburn causes permanent damage to the skin and causes skin cancers like squamous cell cancer (SCC), basal cell cancer (BCC) and melanoma. But the use of sunscreen alone will not reduce the incidence of skin cancer, especially BCC and melanoma. You should avoid sunburn by other means wearing appropriate clothings, wide-brimmed hat and appropriate sunglasses and avoid sun exposure between 11 a.m. and 3 p.m.

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How do I know if I have H1N1 flu virus?

Most patients with H1N1 flu virus present with acute respiratory illness. The main presenting symptoms are cough or fever. With this you may have sore throat, headache, eye pain or muscle ache. Just like a human seasonal flu. H1N1 flu virus is a strain of the influenza virus that usually affects pigs but which may also make people sick.

In a review of cases published in the Canadian Medical Association Journal (CMAJ) of August 4, cough was reported in 90 per cent of cases and fever in 60 per cent of cases. The other common symptoms like headache was present in 83 per cent and 76 per cent had nasal congestion and sore throat.

As we know by now, the outbreak of this virus began in Mexico in March 2009. It has only been six months and over 100 countries have reported thousands of confirmed cases and many hundreds have died from this illness. The illness is spreading like a regular seasonal flu. Except this is happening in summer months. The World Health Organization has declared this to be a pandemic flu. That means the disease is prevalent throughout an entire country, continent or the whole world.

During a regular season flu, 4000 Canadians die each year. H1N1 virus flu is expected to cause thousands of deaths if it spreads like a wild fire. Some research on the Internet reveals that the influenza pandemic of 1918-1919 killed more people than the Great War, known today as World War I (WWI), at somewhere between 20 and 40 million people. It has been cited as the most devastating epidemic in recorded world history.

Every person is susceptible to this virus. People with low immunity and chronic disease are more susceptible. As a group, children are two to three times more likely than adults to be infected by any flu virus each year. It is also interesting to note that children carry more live viruses in their respiratory secretions than adults do and for twice as long. When children catch the flu they readily pass it over to their families and communities — perhaps because they aren’t always careful about covering their noses and mouths when coughing or sneezing.

Pregnant women are no more likely to get the flu, but are prone to greater risk than general population for developing complications from it. Pregnant women are four times more likely than the general population to need hospital treatment for H1N1 swine flu. The risk is higher in the second half of the pregnancy.

How do I protect myself against H1N1 flu virus? The Public Health Agency advises Canadians to:
-Wash hands thoroughly with soap and warm water or use hand sanitizer
-Cough and sneeze in your arm or sleeve
-Keep doing what you normally do, but stay home if sick
-Check www.fightflu.ca for more information
-Check www.voyage.gc.ca for travel notices and advisories
-Talk to a health professional if you experience severe flu-like symptoms

H1N1 virus flu is treatable. There two prescription antiviral drugs, oseltamivir (Tamiflu) and zanamivir (Relenza) that are effective in treating the flu virus. Public Health Agency of Canada (PHAC) recommends that antivirals be used to treat H1N1 flu virus when the illness is moderate to severe and the patient is at a great risk for complications.

PHAC also says that it is unlikely the seasonal flu shot will provide protection against H1N1 flu virus. A new pandemic vaccine will be available to all Canadians who need and want to receive it.

NEW: November 3, 2009:
Ten Reasons Why I Had H1N1 Vaccine

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Shingles is an Ugly and Painful Condition

Recently, a relative sent me a picture of his face, full of blisters, on the right side, below the lower eyelid. The blisters went all the way to his upper lip. He said it was very painful and he had lost sensation in the right side of the face and upper lip. He was feeling lousy and had no appetite. He could not drink anything hot or too cold because of the loss of sensation. There was constant headache.

This is a classic case of herpes zoster, commonly known as shingles. Now, do not confuse this with the shingles on the roof of your house or a short hair cut on a pretty lady. Shingles does not look pretty and unlike your shingles on the roof it does not provide any protection.

Shingles is caused by varicella zoster virus (VZV). This is the same virus which causes chickenpox. The first indications that chickenpox and shingles were caused by the same virus were noticed at the beginning of the 20th century.

This is what happens. The virus causes chicken pox which generally occurs in children. Once the child gets over the illness the virus does not disappear from the body. Virus can settle down in one of the nerve cell bodies and lay dormant for many years.

When your resistance is low and this can be due to any reason, the virus may break out of the nerve cell and travel down the nerve causing viral infection of the skin in the area supplied by that nerve. This can happen decades after the chicken pox infection. Exactly how the virus remains latent in the body, and subsequently re-activates is not understood.

Early symptoms of shingles are non-specific like headache, fever and malaise. Then there is burning pain, itching and tingling followed by painful rash and blisters in the area supplied by the affected nerve. The pain and rash most commonly occurs on the torso, but can appear on the face, eyes or other parts of the body. If the nerve to the eye is involved then a person may suffer loss of vision.

The rash and blisters heal within two to four weeks but some sufferers experience residual nerve pain for months or years. This condition is known as post-herpetic neuralgia. About 20 per cent of patients with shingles suffer from this.

If the diagnosis of shingles is made early then it helps to start anti-viral medications within 72 hours of the appearance of the rash. This reduces the severity and duration of the illness. The anti-viral medications should be used for seven to ten days. The blisters crust over within seven to ten days, and usually the crusts fall off and the skin heals. But sometimes after severe blistering, scarring and discolored skin remains.

Although a person of any age can suffer from shingles, aging population and individuals with poor immunity (AIDS, renal failure, stress) are more prone to shingles if they have had chickenpox in their younger days.

Is it contagious? Yes, to a point. Until the rash has developed crusts, a person is extremely contagious. During the blister phase, direct contact with the rash can spread the virus to a person who has no immunity to the virus. This newly-infected individual may then develop chickenpox, but will not immediately develop shingles.

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Blood Clots in the Legs can be Dangerous

Dear Dr. B: Few days ago I returned from a European holiday with pain and swelling of my right leg. My doctor did some tests and said I have deep vein thrombosis. Now I am on blood thinners. Can you please explain what deep vein thrombosis is?

Answer: Blood clots in the leg veins are not an uncommon problem. A blood clot in a superficial vein is known as superficial thrombophlebitis. This condition is usually not serious or life threatening.

A blood clot in a deep vein of a leg is known as deep vein thrombosis (DVT). This is a serious condition as the clot may dislodge, travel through the blood stream and plug a vessel in the lung (pulmonary embolism). Pulmonary embolism (PE) can be fatal.

The calf muscles act as a second pump (first pump being your heart). The contraction of the calf muscles and the valves in the deep veins help push the blood from the lower extremity towards the heart.

DVT occurs when the blood moves through deep veins in the legs more slowly than normal or when there is some condition that makes blood more likely to clot. Two common examples are: when you are bedridden (after surgery, injury or chronic illness) or when you sit still for a long time (such as during a long plane flight or a long road trip). Under these conditions the blood moves more slowly and stagnation promotes clotting.

Obesity, cancer and smoking cigarettes also increase the risk of DVT.

Blood thinners (anticoagulants) like heparin and warfarin are used to treat DVT and prevent pulmonary embolism. The blood thinners do not dissolve the clot. They stop the clot from getting bigger, prevent the clot from breaking off and reduce the chances of having another blood clot.

The most common and sometimes very serious side effect of anticoagulant therapy is bleeding. Blood tests will check how well the medicine is working. If you bruise or bleed easily while on blood thinners then talk to your doctor and get a blood test done.

The risk of having recurrent DVT depends on the risk factors as outlined earlier. Generally speaking, if you have had DVT once then this does increase the risk of another DVT.

Clinically or radiologically there is no test to confirm if the clot is completely dissolved. The body takes its own time to dissolve the clot or the clot may get organized and form scar tissue, permanently blocking the vein or damaging the valves. Warfarin does not dissolve the clot. Normally, no tests are done to check if the clot is still present as the tests can be inconclusive or confusing.

When travelling, stay hydrated so your blood does not become thick. It is important to stay mobile. If sitting in your vehicle or in a plane during long journeys, exercise your ankle every few minutes so the calf muscles can push the blood toward your heart. This will prevent stagnation of blood in your calf.

Enjoy the summer and be safe. Don’t forget, you need lots of fluids, sunscreen and DEET.

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