The first doctor to question the itching was Hippocrates: symptom or disease autonomous in its own right? After more than two thousand years, and 'concluded that the itching, one of the most' annoying attributable to many skin diseases but also internistiche and neurological, is a subjective symptom. Despite this', but it should be 'recognized and that no' yet reached its exhaustive and comprehensive framework nosography. Even its definition suffers from a certain dose of generic ':"unpleasant sensation that provokes the desire to scratch". Little or nothing more 'than it already' in the seventeenth was stated by Haffenrefer so that 'it described" tristis Sensat, wishes scalpendi excitans".
Many have focused on analysis of these simple words, and more 'and parties' emphasized that the reference to the discomfort caused by itching can' take on different meanings depending on the individuals, and that not all patients suffering from itching have always wanted to scratch. Regarding the significance of itching, and 'different feel uncomfortable when taking a positive physiological significance because' through the consequent scratching determines the removal of the trigger potentially harmful, but has a connotation entirely pathological when, for example, is associated with systemic disease, a disorder pschiatrici or use of specific drugs. Without ignoring that, generally, we appeal to indistantamente term itching is if there are skin lesions that warrant (excoriation, lichenificazioni, keratosis), both in their absence (sine field). In a situation like 'little defined, see what information that some refer to as itching and biochemical mechanisms, cellular and neuroanatomici common to most forms' notes and more' spread. We start by saying that the experience of a feeling of itching can 'hit everyone, regardless of age' and sex, but can 'be lived only on the skin and what' due to its particular structure neuroanatomica of this body. The intensity 'can vary from mild to very severe forms, with difficulty sleeping, irritability' problems in normal daily life. Regarding the duration, can 'occur in acute or chronic, localized to very specific areas such as the scalp, the ano-genital area, the arts, etc.. or generalized. More 'studies show a close relationship between psychiatric disorders and itching, both as causes that lead to stress that it is determined in the manner most' prolonged and severe. In 1936 Huet classifies' the causes of itching in three categories, still valid. predisposing causes, including genetic factors and allergies, in addition poisoning endogenous and exogenous. . environmental factors such as temperature, humidity ', the wind and emotions. . physical, chemical, infections, infestations and more. Although lacking an animal model, knowledge increased itchy are, in particular as a result of studies conducted to understand the mechanisms of pain, and today we know much more 'on possible triggers exogenous agents (mechanical, electrical, thermal and chemical) and diseases that can join (inflammation, hypersensitivity ', degenerative forms, neoplasms, psychosis, etc.).. Today we know that many internal and neoplastic diseases may be associated with itching and dry skin (asteatosi, xerosi, atopy) so 'as the excessive use of bathrooms and too hot can cause this unpleasant nuisance, especially in people over' elderly. In these cases to determine the itching would mneccanismi neccanici or osmotici. Basics of Neurophysiology itching exclude specific receptors, while the points which are manifested by nerve endings free intra-epidermal and those close to derma-epidermal junction. The impulse is tramette in the central centripesica lap later. Studies carried out by the technique of PET also showed activation of a pre-motor and inferior parietal lobe, and synaptic connection to the motor brain that probably lead to scratching. Until recently it was thought that itching was a mild form of pain and you pass through the same nerve endings. A deposit for this theory was the finding that a local anesthetic that cutting the sensitive nerve pruriginosa abolish both perceptions. And subsequently 'made clear that the mode' differ and while scratching the itching induced, the pain causes a reaction of flight. Also: morphine removes the pain but can cause itching, and heat over 41 ° suppress the itch but not the pain, and finally, removing the skin layer and the more' surface of the skin removes the itch but not the pain . There is no single chemical mediator of itching, and certainly histamine alone is not 'can explain all forms. e 'pero' interesting to know that this amine, present within many of mastcellule metachromatic granules, when applied in epidermide or alivello basal membrane determines itching, and if it is granted more 'in depth' in the dermis, and 'Case pain and angioedema. Some experiments confirmed that serotonin, in this cute little, if injected into the dermis can 'cause itching and pain. Other mediators, alone or in combination, are regarded as potential trigger factors itching: proteinases, prostaglandins, neuropeptide, bile salts and cytokines. In outbreaks of inflammation are usually many antibodies endopeptidasi (papain, trypsin, chymotrypsin, kallikrein, plasmin) can trigger itching without mediation by istamina. Among the prostaglandin PGE2, a vasodilator in this injury as a healing, per se 'does not cause itching, but lowers the threshold and enhances the itching caused by istamina. After sun exposure, and it 'The incidence involved in training and itching and responds in part to the antiistaminici. The Substance P, neuropeptide proinflammatory formed by 11 amino acids, produced in the dorsal ganglia and then transported to the outskirts via fiber nocicettive Ae C encourages the issue by istamina by granules of mastcellule and thereby induce itching, which can 'be experimentally inhibited by a previous administration of antiistaminici orally. In the cute Substance P can 'also cause erythema, swelling and inflammation neurogenica through the release of histamine, IL-1, lysosomal enzymes and prostaglandins, but is easily degraded and inactivated in the dermis. The Capsaicin, a substance contained in chilli, applied locally Abass levels of substance P contained in the nerve endings reducing the itching. Among the cytokines, the interluchina 2 administered orally or intravenously cause itching. The same is known for bile acids, especially being an obstructive jaundice, but recent studies have shown that over these molecules also opioids such as b-endorphins, the encefaline met-leu-and encefaline assume an important role trigger in itching, acting locally and systemic way. A few words on the Melzak Wall and the scratching is a reflex arc sinaptico outside the control of the cerebral cortex, which would cause a circuit inhibition of itching to spinal or central level. Even lowering the temperature to 29.7 degrees and substances such as menthol reduce the intensity 'of itching with a central inhibitory effect. In conclusion, and not 'bold to say that the itch is one of the challenges more' challenging for any doctor. I know the dermatologists, but the frustration of failure therapeutic escape internists, pediatricians, psychiatrists and, very often, doctors base. Frequently s'intraprendono diagnostic pathways gradually more 'complicated, almost led to exclusion, but this process slow and not very rewarding and' almost impossible to relinquish. Why 'at the end of history, according to the specialists, only a correct diagnosis can' afford an accurate and effective treatment.