<p>But summer has its share of unpleasant discoveries, too — as dermatologists know all too well. For this is also the season of the mystery rash. <br /><br />In truth, many of these rashes are not at all mysterious. Very often, dermatologists find, they result from a photosensitivity reaction, a combination of the sun’s UVA radiation and exposure to a drug, perfume or some other substance.<br /><br />Many commonly-used drugs can cause such a reaction, including antibiotics like the tetracycline’s (doxycycline is one), ciprofloxacin and the sulfa drugs; the diuretic hydrochlorothiazide azide, and over-the-counter anti-inflammatory drugs, like ibuprofen and naproxen.<br /><br />People with the photosensitive reactions “may have been on the drag for a long time, so they don’t put two-and-two together,” said Dr Deborah, senior vice president of the Skin Cancer Foundation, in the US.<br /><br />The list of substances that can trigger a photosensitive reaction is very long and includes, ironically, sunscreens that contain benzophenones, the retinoids used to treat acne, and sun-induced wrinkles, and fragrances like musk and coumarin.<br /><br />The guilty substances change with the times, as compounds go in and out of fashion. But the problem never vanishes. New irritants frequently appear in products, keeping dermatologists on their toes and consumers mystified.<br /><br />Most photosensitivity reactions result from exposure to UVA radiation, the so-called tanning rays that have been linked to premature aging of the skin and to melanoma.<br />UVA radiation can pass through window glass, so a reaction can occur following a car ride or sitting indoors near a window, further mystifying affected individuals. And though the sun is the most common source of UVA radiation, it is not the only source. This type of radiation is found in tanning booths and, in small amounts, fluorescent bulbs.<br /><br />Photosensitivity — “a broad umbrella,” Dr Sarnoff said — refers to two types of reactions. One, the kind that can happen to any-one, is called phototoxic, the effects of which resemble a very bad sunburn. It can occur the first time a person is exposed to a trigger.<br /><br /> The culprit, like many of the substances mentioned above, may be ingested or applied topically. It gets into the skin, where it is activated by UVA rays. Within a day, the sun-exposed skin turns very red.<br /><br />While in theory anyone exposed to sufficient amounts of a phototoxic drug should react to UVA exposure, one’s susceptibility can be influenced by such factors as the amount of drug present in the skin, the colour and thickness of the skin, and environmental conditions like humidity, temperature and wind.<br /><br />The second type of photosensitivity reaction, called photo allergic dermatitis, is much less common, affecting 1 to 2 per cent of the population. It is what doctors call a delayed hypersensitivity reaction that more often results from application of topical substances, like perfumes, that can induce allergic reactions.<br /><br />In a 20-year study of 69 people with documented photo allergic dermatitis, doctors at New York University School of Medicine found that antibiotics and ingredients in sunscreens each caused 23 per cent of the reactions. <br /><br />Unlike phototoxic reactions, which require a rather strong exposure to the offending substance, a photo allergic response can result from relatively small amounts of the allergen.<br /><br />A photo allergic reaction doesn’t show up until two or three days later, so sufferers may not link it to sun exposure. The irritation can spread to areas of the body that were not exposed to the sun. The rash may be itchy at first, then, like poison ivy, turn into watery blisters.<br /><br />Determining the cause of a reaction is likely to start with an inventory of the substances you are exposed to that are common culprits. Were you on an antibiotic, or do you take a thiazide diuretic or a nonsteroidal anti-inflammatory drug? Have you recently begun using a new scent or sunscreen? Might you have been working with a particular plant? A photo patch test, similar to that used by allergists to test for allergic sensitivities, can confirm sensitivity.<br /><br />The best way to deal with a photo-sensitivity reaction is to sidestep it. If at all possible, avoid exposure to the substance that caused it. If a medication was responsible, ask your doctor if you can switch to an alternative. If it resulted from a drug that you must take, you will have to avoid UVA exposure.<br /></p>
<p>But summer has its share of unpleasant discoveries, too — as dermatologists know all too well. For this is also the season of the mystery rash. <br /><br />In truth, many of these rashes are not at all mysterious. Very often, dermatologists find, they result from a photosensitivity reaction, a combination of the sun’s UVA radiation and exposure to a drug, perfume or some other substance.<br /><br />Many commonly-used drugs can cause such a reaction, including antibiotics like the tetracycline’s (doxycycline is one), ciprofloxacin and the sulfa drugs; the diuretic hydrochlorothiazide azide, and over-the-counter anti-inflammatory drugs, like ibuprofen and naproxen.<br /><br />People with the photosensitive reactions “may have been on the drag for a long time, so they don’t put two-and-two together,” said Dr Deborah, senior vice president of the Skin Cancer Foundation, in the US.<br /><br />The list of substances that can trigger a photosensitive reaction is very long and includes, ironically, sunscreens that contain benzophenones, the retinoids used to treat acne, and sun-induced wrinkles, and fragrances like musk and coumarin.<br /><br />The guilty substances change with the times, as compounds go in and out of fashion. But the problem never vanishes. New irritants frequently appear in products, keeping dermatologists on their toes and consumers mystified.<br /><br />Most photosensitivity reactions result from exposure to UVA radiation, the so-called tanning rays that have been linked to premature aging of the skin and to melanoma.<br />UVA radiation can pass through window glass, so a reaction can occur following a car ride or sitting indoors near a window, further mystifying affected individuals. And though the sun is the most common source of UVA radiation, it is not the only source. This type of radiation is found in tanning booths and, in small amounts, fluorescent bulbs.<br /><br />Photosensitivity — “a broad umbrella,” Dr Sarnoff said — refers to two types of reactions. One, the kind that can happen to any-one, is called phototoxic, the effects of which resemble a very bad sunburn. It can occur the first time a person is exposed to a trigger.<br /><br /> The culprit, like many of the substances mentioned above, may be ingested or applied topically. It gets into the skin, where it is activated by UVA rays. Within a day, the sun-exposed skin turns very red.<br /><br />While in theory anyone exposed to sufficient amounts of a phototoxic drug should react to UVA exposure, one’s susceptibility can be influenced by such factors as the amount of drug present in the skin, the colour and thickness of the skin, and environmental conditions like humidity, temperature and wind.<br /><br />The second type of photosensitivity reaction, called photo allergic dermatitis, is much less common, affecting 1 to 2 per cent of the population. It is what doctors call a delayed hypersensitivity reaction that more often results from application of topical substances, like perfumes, that can induce allergic reactions.<br /><br />In a 20-year study of 69 people with documented photo allergic dermatitis, doctors at New York University School of Medicine found that antibiotics and ingredients in sunscreens each caused 23 per cent of the reactions. <br /><br />Unlike phototoxic reactions, which require a rather strong exposure to the offending substance, a photo allergic response can result from relatively small amounts of the allergen.<br /><br />A photo allergic reaction doesn’t show up until two or three days later, so sufferers may not link it to sun exposure. The irritation can spread to areas of the body that were not exposed to the sun. The rash may be itchy at first, then, like poison ivy, turn into watery blisters.<br /><br />Determining the cause of a reaction is likely to start with an inventory of the substances you are exposed to that are common culprits. Were you on an antibiotic, or do you take a thiazide diuretic or a nonsteroidal anti-inflammatory drug? Have you recently begun using a new scent or sunscreen? Might you have been working with a particular plant? A photo patch test, similar to that used by allergists to test for allergic sensitivities, can confirm sensitivity.<br /><br />The best way to deal with a photo-sensitivity reaction is to sidestep it. If at all possible, avoid exposure to the substance that caused it. If a medication was responsible, ask your doctor if you can switch to an alternative. If it resulted from a drug that you must take, you will have to avoid UVA exposure.<br /></p>
