Infection caused by a dermatophyte fungus is called lichen. Microscopic organisms live on the skin, namely in the hair follicles. The fungus responsible for ringworm is found in the soil, which is why cats and large cattle are most often infected. Controversy persists environment up to two years even garden tools, shoes, carpet paths.
Children who try everything with their hands, and sometimes with their teeth, are exposed to infection due to weak immune system. The disease is transmitted to humans through domestic animals or from an infected environment. Athlete's foot and groin most often spread in public locker rooms and swimming pools.
Lichen appears as a small lesion with scaly skin in the center. Gradually, it grows, causing hair loss. The lesions are not always round, and the hair does not always fall out completely. Baldness can be accompanied by redness and inflammation. Hair can grow even during the presence of an infection on the body, so the disappearance of bald spots does not indicate a cure.
More accurate methods are required for diagnosis. Dermatologists often study pathological changes in the skin under the Wood's lamp to choose a further direction of examinations or to confirm their own guesses.
fluorescent lamp
The Wood's lamp is a diagnostic tool in which the affected skin, under the influence of black light, causes a certain glow. Black light is waves invisible to the naked eye. ultraviolet spectrum that glow purple in the dark.
The traditional Woods lamp was equipped with a mercury coating for 320-450 nm radiation and was invented in 1903 by physicist Robert Wood. Modern black light sources are developed on the basis of fluorescent, mercury, light emitting lamps, diodes or incandescent lamps. It is the dark blue coating on the tube that filters out most of the visible light waves.
Luminescent diagnostics
To diagnose skin problems under the Wood's lamp, you need to follow a few steps:
- Wash the skin, remove make-up, moisturizers and other cosmetics, as it can cause a false positive result.
- Turn on the lamp to warm up for a minute.
- Turn off the lights in the office and curtain the windows to create darkness.
- When the vision adapts to the darkness, direct the light of the lamp to the skin at a distance of 10-30 cm.
The fluorescent color allows you to detect pigmented or depigmented spots.
Normal healthy skin glows light blue color, thickened areas appear white, oily areas appear yellow, and dehydrated skin turns purple.
To distinguish lichen contagious from other skin lesions, a Wood's lamp is used. The test result is positive if the pigmentation becomes more pronounced during the test.
Glow Features
Fluorescent black becomes visible when collagen or porphyrins absorb it and emit it in the visible spectrum. Threads, hair, preparation, and soap residue on the skin may also fluoresce.
What color does lichen glow under ultraviolet light for various skin pathologies:
- Increased pigmentation (melasma, post-inflammatory pigmentation). The lesions have clear boundaries under the light of the lamp due to an increase in the level of melanin in the cells.
- Loss of pigmentation (vitiligo, tuberous sclerosis, hypomelanosis) should be detected in fair-skinned people. The lesions will glow bright blue (sometimes yellowish green) due to the accumulation of biopterins. Areas with reduced blood flow do not change under light.
- Pityriasis versicolor is a mildly scaly persistent rash on the front of the chest and back caused by fungi. Under the light, the lamps glow orange or yellow. Pityriasis versicolor breaks pigmentation under the action of the fungus, and its spots become more pronounced under ultraviolet light.
- In folliculitis caused by the yeast Malassezia, the hair follicles emit a bluish-white light.
- Glow with ringworm depends on the type of fungal infection: with microsporia it is blue-green (M canis, M. audouinii, M distortum), and with trichophytosis it is pale blue. Fungal infections caused by other organisms do not fluoresce
- Erythrasma, caused by corynebacteria, is accompanied by a pigmented rash in skin folds that turn coral pink.
- Lichen planus is diagnosed by the appearance of whitish-yellow spots.
- Pink and herpes zoster are examined with a Wood's lamp for differential diagnosis only. The herpes virus is confirmed by the detection of DNA by polymerase chain reaction in the fluid that is taken from the blisters of the rash. Inflammatory processes are highlighted in white, which can also indicate an immune response to viruses or bacteria.
Wood's lamp directs diagnostics in the right direction. The most contagious type of fungus that causes lichen is microsporum. To confirm infection, bakposev is carried out in the laboratory, requiring at least 10-14 days. Therefore, a fluorescent lamp with a Wood filter acts as a method of express diagnostics.
Fresh lesions of ringworm on the hair may not be detected with a lamp, because the signs of damage are minor. The dermatologist recommends that hair be removed from the suspected site of infection in order to examine the roots. Even after the death of the fungus, the hair continues to glow.
Diagnostic Rules
Wood's lamp helps to identify foci of lichen on smooth skin, hair, nails, eyebrows. The dermatologist uses a protective mask or goggles to protect the eyes from the direct radiation of the lamp. The patient will be asked to close their eyes. The procedure lasts an average of 1-2 minutes, does not require additional actions on the part of the patient. Sometimes a microscope is used to examine the condition of the skin in detail.
It must be remembered that a fluorescent examination only supplements the basic diagnosis, allows you to suspect a certain disease.
So a glowing white focus means inflammation, vitiligo, candidiasis, systemic lupus erythematosus. Therefore, differential diagnosis requires taking a scraping and analyzing the material under a microscope.
The experienced eye of a dermatologist is able to identify the shade of a particular pathology. At home, the Wood's lamp can refute or confirm the need to see a doctor when a rash appears on the body or head.
UV treatment
If fungal infections can be diagnosed ultraviolet lamps, then other skin lesions are amenable to physiotherapy of the same name. The herpes virus that causes shingles is sensitive to ultraviolet light. Therefore, dermatologists use physiotherapy procedures that contribute to the gradual disappearance of spots. Pink lichen can be cured on its own, even in a solarium, if it does not respond to therapy and is prone to relapse.
Most people, when asked "What is luminescence?" remember fluorescent gas discharge lamps. Indeed, this is one of the most famous applications of a bright (literally) physical phenomenon, namely photoluminescence (excitation by light). The glass tubes contain mercury vapor excited by an electric discharge and emitting in the ultraviolet region. Coated on the walls of the tube - a phosphor - converts ultraviolet radiation into radiation visible to the human eye. Depending on the type of phosphor, the color of the glow can be different - this makes it possible to produce lamps not only of "cold" and "warm" light, but also different colors- red, blue, etc. Appeared in recent times energy-saving lamps, superior to incandescent lamps in the visible light, are the same fluorescent lamps, only greatly reduced due to the miniaturization of electronics. Another type of luminescence is cathodoluminescence. It is this principle that underlies cathode ray tubes: the phosphor covering the screen glows under the action of an electron beam. X-ray luminescence, for example, is used when performing fluorography - a screen covered with a phosphor glows under the action of x-rays.
According to the definition given in Physical Encyclopedia, luminescence radiation, which is an excess over the thermal radiation of the body and continues for a time significantly exceeding the period of light oscillations. The first part of the definition separates luminescence from thermal equilibrium radiation and shows that this concept is applicable only to a set of atoms (molecules) that are in a state close to equilibrium. With a strong deviation from the equilibrium state, it makes no sense to talk about thermal radiation or luminescence. In the visible region of the spectrum, thermal radiation becomes noticeable only at a body temperature of thousands of degrees, while it can luminesce in this region at any temperature, which is why luminescence is often called cold glow. The second part of the definition (a sign of duration) was introduced by S.I. Vavilov to separate luminescence from various kinds scattering, reflection, parametric transformation of light, bremsstrahlung and Cherenkov-Vavilov radiation. In contrast to light scattering, during luminescence, intermediate processes occur between absorption and emission, the duration of which is longer than the period of the light wave. As a result, during luminescence, the correlation between the phases of the oscillations of the absorbed and emitted light is lost.
Fast and slow
After the termination of excitation, the luminescence decays. If this happens quickly, then the process is referred to as fluorescence (from the name of the mineral fluorite, in which this phenomenon was discovered), and if the glow continues long time- then to phosphorescence. Fluorescence under the action of light (visible and UV) can often be observed in everyday life - marker dyes, road sign coatings and workwear fabrics glow. It is fluorescence that is responsible for the fact that freshly washed White shirt seems to be bright sunshine"whiter than white". And this effect is not psychological. Just washing powders contain special substances, optical brighteners, which, under the influence of ultraviolet radiation, emit visible light (usually in the blue-violet region). This explains the fact that white clothes glow under the action of UV lamps in discos. Slowly decaying luminescence (phosphorescence) is also very common in everyday life - remember the clock faces and hands of other instruments (as well as the screens of old oscilloscopes).
And others
In addition to the above-mentioned varieties, there are radioluminescence - under the action of penetrating radiation (used in scintillation counters), chemiluminescence under the action of chemical reactions (including bioluminescence), candoluminescence (under mechanical influences), lioluminescence (during the dissolution of crystals), electroluminescence (under the action of electric field), etc. Some of them are quite familiar to readers. For example, the glow of white phosphorus is the result of chemiluminescence: oxidized under the action of atmospheric oxygen, phosphorus vapor glows. Oxidation also explains the glow of plastic "flashlights" - chemical light sources, only they use not phosphorus and oxygen, but an organic dye and hydrogen peroxide.
There are no secret labels.
Luminescence under the influence of ultraviolet is actively used to verify the authenticity of various documents, forms and banknotes. Now almost every cashier has a machine with a UV lamp at hand to check banknotes. This method has been used since the beginning of the 20th century, Robert Wood, the famous American physicist, experimented with it at the end of the First World War. Here is how Wood himself describes it in the book of his biographer William Seabrook “Robert Wood. The Modern Magician of the Physics Laboratory":
... They [the Bureau of the Chief Censor of the British Navy] proudly told me that they had invented paper on which it was impossible to make an "invisible" secret record. It was sold in all post offices, and letters written on it could not be subjected to any tests. This paper became very popular as the letters were not censored. It was regular stationery, printed with frequent parallel lines in pink, green, and blue. Red paint was diluted in water, green in alcohol, and blue in gasoline. The paper looked grey. Since almost any liquid in which are dissolved invisible ink, belongs to one of these three classes, one of the colored lines will dissolve in the colorless liquid flowing from the pen, and traces of the inscription will appear. I remembered that Chinese white turns out as black as coal in ultraviolet photographs, and I said: “Suppose I wrote on it with a thin stick with Chinese white - then none of the lines will dissolve, and yet the inscription can be will be read if you photograph the paper.
Marks made with invisible ink that glows in ultraviolet light are very often used to determine the authenticity of various documents. Yes, and the paper itself, as a rule, contains fibers that glow in the ultraviolet.
“Oh no,” they replied, “you can even write on it with a toothpick or a glass rod without any paint. The colored lines are made slightly soft or sticky so they will smudge and become dark gray letters. Here's a glass rod for you - try it yourself! (…)
I said, “Okay. Still I will try. Bring me a rubber stamp and some Vaseline." They brought me a large, smooth, clean stamp of military censorship. I rubbed Vaseline on it, then wiped it hard with a handkerchief until it no longer left marks on the paper. Then I pressed it firmly against the "spy-proof" paper, preventing it from slipping to the side.
"Can you find an inscription here?" I asked.
They tested the paper in reflected and polarized light and said, "There's nothing here."
"Then let's light it up with ultraviolet rays." We took her into the booth and put her in front of my black window. On the paper, in bright blue letters, as if a stamp smeared with ink had been applied to it, the words glowed: "There are no secret inscriptions."
Since ancient times, mankind has tried to invent invisible or, as they are also called, sympathetic ink, which are not visible to the eye under normal conditions, but begin to appear after exposure to any chemical elements, heating, ultraviolet rays. They were used to send secret messages, to keep important information, secret correspondence.
In ancient times, these were commonly available substances that could be found in every home. For example, great success secret writing was used, carried out with the help of milk, lemon juice, rice water, wax, apple and onion juice, swede juice. Later, options for making sympathetic ink using aspirin tablets appeared, blue vitriol, iodine, washing powder.
Modern UV inks
Science does not stand still, so in our time you will no longer surprise anyone with invisible industrial ink. Compounds that glow under ultraviolet lamps are very popular. There are even pens with UV ink on sale, which can be found in spy stores.
An alternative to such a pen can be invisible anti-counterfeiting paints and pigments. They are powdered substances that can be used to mark banknotes, securities, clothes. In daylight, the powder is completely indistinguishable, but in ultraviolet light, every grain or powder becomes noticeable.
How to make invisible fluorescent ink at home
A good fluorescent ink can be a regular laundry detergent containing optical brighteners. Having diluted the powder with a small amount of water, you can begin to write a secret message. The dried solution will not leave prints on paper, but it will be perfectly visible in the light of an ultraviolet lamp.
Also can be purchased separately. As a rule, they are used to give whiteness with a bluish tint to clothes, fabrics, paper intended for printer printing. The powder can also be used to create sympathetic ink. These inks show up on all types of paper.
Another way to make invisible ink is to use aspirin tablets and alcohol. In a small amount of alcohol, 2-3 aspirin tablets should be dissolved. If a precipitate remains during the dissolution, then the liquid should be filtered. After that, you can start secret writing. Such ink does not glow on all types of paper, this method is not applicable if you write on printer paper.
You can also use the following preparations to prepare ink, which you can try to purchase at a pharmacy:
- curcumin;
- quinine sulfate;
- tripoflamin.
Fluorescein sodium salt can also be used, but its native color may stand out on white paper after application, so this ink is not considered invisible.
Few people know, but a grandiose light show is constantly happening around us, which, unfortunately, we do not see. The fact is that many arthropods (insects, spiders, etc.) have one interesting feature: They glow under ultraviolet light.
Fireflies and other animals endowed with the ability of bioluminescence glow due to chemical reaction flowing in special organs of luminescence. Many people have seen this phenomenon. But scorpions, some spiders and a number of related organisms are able to produce a blue-green glow using the phenomenon of fluorescence.
Crab spider fluorescence exoskeleton molecules ( outer shell) these animals absorb invisible to our eyes ultraviolet light(320-400 nm), after which they re-emit ultraviolet already in the bluish light visible to us.
It turns out that many arthropods glow under ultraviolet light. Photographer Nicky Bey (his photographs are used in the pro article along with mine) took a series of wonderful pictures of arthropod bioluminescence, with which I illustrated this text.
Why do arthropods glow in ultraviolet light?
In short, for many of the fluorescent animals, we don't know why. There is a lot of literature about the illumination of various arthropods, the main idea of which can be reduced to: “Wow! It's glowing!!!"
Kivsyaki also fluoresce in UV light True, for scorpions, the mechanism of this glow has been studied in more detail.
In scorpions, the so-called cuticular fluorescence is observed. It involves two compounds found in the epicuticle of the scorpion: beta-carboline and 4-methyl, 7-hydroxycoumarin. Coumarin, by the way, is used in perfumes or as a cinnamon flavor.
The fluorescence of scorpions is a very beautiful phenomenon. There are a couple of hypotheses regarding the purpose of scorpion fluorescence. Most insects can see ultraviolet light, so their world looks very different from ours.
Spider Heteropoda sp. human and insect eyes According to some experiments, scorpions can use the ability to absorb ultraviolet light to find shelter. During the experiment, the scorpions were put on tiny glasses, because of which the animals could not see with their eyes. But as soon as the UV light was turned on, the animals quickly found suitable shelters. Apparently, orientation occurred due to signals received from surface covers that absorbed ultraviolet (published in the journal Animal Behavior).
Maybe ultraviolet helps scorpions navigate According to another version, the glow of scorpions in the ultraviolet is a relic of the early Devonian period, when giant scorpions and centipedes inhabited the earth. The substances accumulated in the integument, capable of absorbing ultraviolet and emitting blue light, could protect ancient arthropods from sunburn. At least in young plant seedlings, it is coumarin that acts as a sunscreen.