The causes that can provoke dermatoses are extremely numerous. They can originate from external or internal sources. External causes can be: traumas, stings, dust, thermal factors (heat, cold, especially associated with humidity, dryness, and wind), radiations (sunlight, X-rays, radium), chemical factors (medicinal, organic substances of animal and vegetable origin that come into contact with the skin), animal parasites (mites, insects), and plant parasites (pathogenic fungi, various microbes, all part of the external causes that produce dermatoses.
Factors that, although coming from the external environment, act internally include foods, medications, and toxins, microbes that cause general infections with cutaneous symptoms, or focal infections. Along with microbes, intestinal worms can also be noted. Morpho-functional disorders of the organs and systems also play an important role, as well as dry, seborrheic, or hyperhidrotic skin, as well as alkaline skin predispose to some dermatoses.
Gastrointestinal and hepatic disorders, endocrine disorders (especially ovarian and less thyroid, adrenal), blood and vascular disorders can also cause dermatoses. Morpho-functional disorders of the nervous system and the nature of the fundamental processes of the central nervous system, excitement, inhibition, mobility, which together allow the identification of a mode of higher nervous activity, have a particularly important role in the appearance and evolution of many dermatoses. A series of nutritional and metabolic disorders cause or aggravate some dermatoses. Diabetes favors the development of infections, gangrene, cutaneous mycoses; metabolic disorders during gastrointestinal and hepatic diseases, hormonal disorders. Here, deficiencies in vitamins, inadequate nutrition, which can cause skin disorders, should also be included.
Heredity and individual predisposition play an important role. It cannot be ignored that the same cause, acting equally on different people, may cause dermatoses to appear in some of them, while others remain immune, and the skin lesions that occur, although caused by the same cause, often have different aspects. On the other hand, it is known that the same skin lesion can be caused by different causes. There are families in which there are congenital predispositions, constitutional, unmodified by other influences, since the way of life, nutrition, and work are the same. Once the disease appears, it tends to reproduce in the family.
Sometimes, especially when it comes to external factors (heat, cold, chemicals), the connection between cause and effect becomes evident. Other times, for example, when it comes to internal metabolic factors, they are more difficult to identify, and their role is harder to assess.
Often, etiological factors are multiple, and it is difficult to specify which of them are provocative and which are predisposing. In these cases, it is necessary to determine the dominant etiological cause.
Dermatoses caused by insects: Pediculosis is caused by lice, parasites that are part of the class of insects. There are three varieties of lice, according to their shape and size, according to the type of lesions they cause, and according to their localization. Thus, head lice, body lice, and those localized in hairy regions can be found.
Among other insects causing skin eruptions are fleas, bedbugs, or woodlice, mosquitoes.
Bees and wasps produce at the site of the sting a marked pain, followed by redness and swelling of the region. When the stings are numerous, the pain is more intense, the swelling more pronounced, all being accompanied by serious general phenomena, fever, dyspnea, asthenia, and sometimes even death.
Caterpillars also cause pruritic skin eruptions on humans, erythematous and vesicular, which can generalize. The lesions are mostly linear, due to the path traveled by the insect, which deposits its irritating venom from its subcutaneous glands through its hairs.
Scabies or scabies is a dermatosis caused by the parasite called the scabies mite. In general, the infection starts from the female, who deposits her eggs in the thickness of the horny layer. For this purpose, it pierces the epidermis with its beak and enters it, where it gradually digs a gallery, from which it cannot get out, eventually dying at the end of this trench, not before laying eggs, which in a few days turn into larvae. These emerge through small openings and spread on the surface of the skin, where after a few more days, they turn into nymphs. During all this time, nymphs, males, and females spread all over the body, pierce the skin to feed, and give rise to a series of other lesions.
Ticks are larger mites up to 4mm in length, which attack all animals and humans who live more in forests. Through the bites of larvae or adults, these parasites cause a series of pruritic lesions in humans, which can lead to complications. Because when the parasite bites, it remains embedded in the skin, it is not advisable to pull it out violently, as it can give rise to cutaneous suppurations.
Spiders can also cause inflammatory and painful lesions through their bites, especially nocturnal ones, after an incubation of 24 hours, in the middle of which inflammatory blisters appear with a reddish-purple exudate, which then leave behind ulcers that heal by scar formation.
Dermatoses produced by bacteria: Leprosy is a chronic, generalized infectious disease caused by the Hansen's bacillus. It is mainly localized on the skin, peripheral nervous system, but also affects the lymphatic system and various organs. The evolution is long, chronic, with outbreaks and remissions, often fatal, death occurring through visceral lesions or intercurrent infections. Leprosy is a contagious transmissible condition.
Dermatoses caused by physical agents: Normal skin, by its structure, is capable of withstanding external physical and chemical stimuli up to a certain intensity. After these stimuli become too intense, the body reacts differently, depending on the nature of the stimulus. Reactions to external physical and chemical agents are generally limited to the action site of that agent.
Mechanical agents acting with low intensity produce lesions that only affect the epidermis and heal without scarring. Such lesions are erosions, excoriations, exulcerations consecutive to scratching caused by pruritic diseases. When the respective traumatic agent acts more intensely, the lesions affect the dermis and hypodermis, giving the appearance of wounds, bruises, hematomas.
Intermittent, repeated pressure for a long time produces inflammation, skin pigmentation, and as a process of physiological adaptation, hyperkeratosis occurs, which can be of two types: Callus (yellowish or brownish hyperkeratotic lesion, more extensive in surface, discreetly prominent, whose edges merge imperceptibly with the normal epidermis) and Clavus (corn) - a round, well-defined hyperkeratotic lesion, with a diameter ranging from 5-10mm, painful. Corn is prominent but also sinks into the underlying dermis, irritating the cutaneous nerves and causing spontaneous pain and especially under pressure. The hyperkeratotic epidermis is often translucent and very hard, having the consistency of a nail. Permanent pressure can cause ischemic necrosis (bedsore that occurs in immobilized patients).
Dermatoses caused by chemical agents: There are substances that, in certain concentrations, constantly produce skin inflammations or necrosis. Alongside these toxic substances, there are others to which the body reacts only after a previous sensitizing contact. Chemical agents that are toxic only to the skin of individuals sensitized by repeated contacts are called allergens. The skin of these individuals reacts to contact with small doses of allergen, with inflammation typical of eczema. This is the mechanism of many professional eczemas.
Initially, at the site of contact of the chemical substance with sensitized skin, an irritation dermatitis characterized by erythema, edema, and blisters occurs, then later, as sensitivity increases, an erythematous-vesicular eczematous eruption occurs, which exceeds the contact surface. The chemical substance can penetrate the body through the respiratory, cutaneous, intravenous, or intramuscular route. The cutaneous manifestations that arise in this way are called toxidermias or toxicodermias, incorrect terms, as they are not toxic processes, but intolerant. Their clinical type is generally unrelated to the chemical substance in question.
However, some drugs produce quite characteristic rashes. Antipyrine causes various rashes, the most common of which is bullous erythema, characterized by erythematous spots located on the skin, oral, and genital mucosa. Iodine and especially iodides produce a wide variety of skin rashes, which take on almost all aspects of skin reactions. Bromides frequently cause acneiform lesions, which appear as small papules-pustules and often turn into furuncles surrounded by redness. Gold salts produce, besides the characteristic erythroderma, lichenoid and pigmented eruptions. Arsenic gives rise to a series of skin accidents. Sulfonamides produce, among other skin accidents, a nodular erythema.
Psoriasis is a chronic skin condition, with a long-term evolution, characterized by the appearance of red (erythematous), prominent, well-defined plaques, covered with thick scales, pearly-white, easily detachable.
Psoriasis generally affects the extensor areas of the body (elbows, knees, loins, hair insertion area on the scalp), or nails, but psoriasis can affect any other areas of the body. Also, psoriasis can be accompanied by joint involvement - psoriatic arthritis or psoriatic arthritis.
Psoriasis occurs in 1.5 to 3% of the population of a certain region, and recently there has been an increase in the frequency of this disease.