Allergic reaction to food
1) anamnesis, that is to say which food, in the judgment of the patient,
provoked the allergic crisis
2) carry out the skin tests related to the involved food
3) In vitro test
4) Exclusion diet?
The history is fundamental to know if the adverse reaction is immediate or
delayed, that is IgE mediated or if it is a delayed type of immune reaction. In
this case it is good to keep the patient in a diary where he can note the
ingested foods. In the first months of life an allergy towards milk and egg
proteins is possible. In allergic subjects, cross-reactivity towards pollens of
some families and various plant foods is often found. In such cases the contact
with these foods causes an allergic oral syndrome with irritation phenomena on
the lips and the oral cavity, and again with vomiting and diarrhea and colic. In
birch and hazelnut pollinosis, hypersensitivity to apple, pear, apricot, walnut,
cherry, banana, hazelnut, fennel and carrot is frequently found.
It is the skin test with the food involved, that is to say, a drop of the allergic substance is placed on the fly surface of the forearm and is released with a special lancet, without causing blood to escape. The most widely used method is currently that of puncture (prick test) consisting in the application of a drop of allergenic extract on the skin (usually of the forearm) and then sting, through the drop, the superficial layers with a sterile tip of the one millimeter in length. For foodstuffs, a fresh product can be tested using the "prick by prick" technique, by first infusing the lancet into the food to be tested and then proceeding with the usual prick test technique. IN VITRO it is possible to dose the total IgE that in adults must exceed 200 KU / l for positivity and specific IgE, ie towards respiratory or food allergens, depending on whether an allergic reaction to allergens in food is suspected. . In vitro tests The most frequently used laboratory tests in allergy diagnostics are PRIST and RAST. Blood concentration of total IgE (PRIST) varies from 10 to 200 kU / l in non-atopic adult subjects. It should be emphasized that a comparison of normal values does not exclude the diagnosis of allergy. In addition, total IgE increases in other pathological conditions (such as intestinal parasitosis) and physiological conditions (such as in smokers). Today, therefore, it is believed that the determination of total IgE has little clinical significance in allergopathies, while the search for specific IgE (RAST) is much more useful. This last test is used only in particular situations such as in the case of taking antihistamines from the patient or skin lesions in the arms that prevent the execution of the skin prick test. The specific IgE dosage is also used as further study in the case of negative skin tests in the presence of an allergy suggestive clinical history or in the case of a poor correlation between the clinical history and the cutaneous positivity, especially in view of any specific immunotherapy .
Finally it can be used in cases where further
confirmation of skin tests is useful (hymenoptera venom.) Finally, a third
diagnostic level is represented by the elimination and provocation tests which
consist in removing and subsequently exposing the subject to a specific allergen
In respiratory and respiratory tract such as respiratory function, the study of
respiratory function by means of spirometry is particularly important,
especially the measurement of bronchial reactivity, ie the tendency of the
bronchi to close in response to the most various stimuli (from bronchial
infections to inhalation of irritants or allergens.) The availability of
portable breathing gauges with a cost of a few thousand lira (peak flow meters,
PEF assessment) also allows for a home patient control, useful for diagnosis and
even for a more accurate therapy To avoid the provocation tests that, in any
case, must be carried out in the environment p rotetto. They are the gold
standard for diagnosing allergies or food intolerances.
The Patch Test is used in the diagnosis of allergic contact dermatitis and
sometimes can help in the diagnosis of allergies to drugs and atopic dermatitis.
The patch test is generally performed for a preordained series of 40 substances
(haptens), those most commonly responsible for allergic contact dermatitis, to
be applied on the back skin with patches. In addition to the haptens of the
standard series it is possible to test many other substances that are chosen
based on the clinical history and eventual work exposure (household series,
cosmetics, eyelids, dentists, metalworkers, hairdressers, etc.). The patch test
results appear after 24-48 hours and often even longer than two days. If after
72 hours a reddened, oedematous and pruritic lesion has formed, possibly with
small vesicles, the result is positive. The patch test does not apply during the
summer as excessive sweating would impair the holding of the patches and the
reliability of the results. Further contraindications are the presence of skin
lesions in the test area and the therapies in place with antihistamines and
especially cortisone. Desensitization. It is a technique of which prof.
Patriarch is one of the main advocates and consists in the desensitization of
allergenic substances through the use of allergen-level doses, for example for
milk it can be started by administering a drop for two / day (eg milk) and
reaching 108 days at 150 ml.
Anaphylaxis: begins with itching of the hands, arms and widespread erythema, hypotension, up to shock. It is important to intervene immediately. Eg after injection of local anesthetic, 2% of subjects may present anaphylaxis. Exercise dyspnoea may appear as a result of the ingestion of an allergic food, which may result in respiratory ambasciation, for example after a meal with consumption of crusty, strawberries, peanuts, etc. The allergic march is an evolving clinical picture that is observed in the atopic child and begins with eczema, proceeds with allergic rhinitis and continues with asthma if not intervened properly, with care and prevention. Prevention When a diagnosis of an allergic disease has been made, it is necessary to: a) Eliminate the patient's exposure to the responsible substance and / or by specific therapy. The elimination of the responsible agent is fully achievable only in a limited number of cases and for some allergens (drugs, food, animal forfore, etc.). In reactive drug syndromes an essential provision consists in the immediate suspension of the responsible medications and in their substitution with alternative drugs. In allergic syndromes from food or food additives, it will be necessary to carefully exclude from the diet all products in which traces, even minimal, of the substances responsible can be found. In inhaled respiratory allergies, elimination of patient exposure to responsible allergens is not always possible. In the pollinosis the stay can be recommended during the period of the clinical symptomatology, in marine places, where the maximum benefit is obtained in the hours in which the wind blows from the sea, channeling air without pollens. These patients should avoid, in the same periods, long trips by car or train with the windows open and the ventilation of the interior during the hottest hours, when pollen concentration in the atmosphere is highest. Furthermore, within certain limits, the installation of air conditioners, which are able to reduce the concentration of pollen in the filtered air, can be advantageous. In respiratory allergies caused by dust mites or other environmental allergens, the patient should be advised to improve the hygienic conditions of the home by frequently ventilating the rooms, carefully removing dust from floors and furniture and eliminating various dust receptacles (carpet, curtains, shelves and books) especially from the bedroom. Particular attention should be paid to mattresses and pillows, which should be replaced with anti-allergic products or, better, covered with anti-mite pillowcases. Blankets and sheets should be frequently exposed to air and sunlight and carefully beaten; the bedroom must be kept cool and dry (the warm-humid climate favors the growth of the Mites). We also recommend the removal of domestic animals (cats, dogs, etc.), especially in cases of subjects with ascertained hypersensitivity to forfore, epithelium or other animal derivatives, but also for the high allergenic power of the same, so it can easily come to create a new awareness, and for the ease with which environmental allergens can be carried by animals, resulting in greater exposure of patients. Mites. They are present in house dust, as was suggested for the first time in 1921. However, the relationship between house dust and house dust allergy was only definitively established in the period from 1962 to 1969 thanks to the studies of Voorhorst, Spieksma-Boezeman MY and Spieksman F.Th.M. Mites are among the oldest living things on earth; they can live and grow in different environments such as plants, flowers, animals, man, the earth, on lakes and salt water, in homes and in organic waste, in mattresses, in books, etc.
Mites are small arthropods belonging to different species. Species that are particularly related to asthma are collectively called "house dust mites", as they have their permanent habitat in the home environment. The mites are part of the phylum of the arthropods because they have an exoskeleton and have the appendices divided into articles. They have small dimensions, about 0.5 mm and their most conspicuous characteristic and a reduction in the segmentation of the body, fundamental property of the other arthropods. They are distinguished from insects because adults have eight legs instead of six. Their dimensions are about 200-300 microns, that is about 1/4 of a millimeter, so they can not be seen with the naked eye, but only with a strong magnifying glass or, better, under a microscope. The male is slightly smaller than the female. The hard chitinous and translucent skin allowing the internal organs and hemolymph to impart an overall white-creamy appearance to the body, with some isolated pale yellow patches. The sclerotic areas, such as the legs and head of fully developed adults, are decidedly more pigmented with a reddish-brown color that stands out on the rest of the body. The most surprising and aesthetically pleasing aspect of the skin and the presence of a sculpted design that resembles that of fingerprints. The dust mite is devoid of a real head; the front part of the body or gnatosoma acts as a buccal apparatus, as well as having gripping and sensory functions. The eyes are absent and although there are no obvious light receptors, dust mites are extremely photophobic and become very animated looking for dark recesses when they are exposed to light. Mites are separated by gender; sexual dimorphism is often accentuated and even if there are some exceptions, reproduction and sexual intercourse. The sexual organs can have very complex structures, especially in the males, in which there is always the presence of an organ called the penis, of different form in the different species. The penis in the simplest case has the shape of a small cylinder protected during rest by a membranous sheath. The information that can be deduced from the monitoring and from the pollen calendars is a useful tool to implement the treatment of pollinosis in the most rational way, being able to know when it should be started or stopped and when it should be appropriately enhanced in relation to the degree of exposure to pollens. . Very often the use of therapeutic measures of various kinds is still inevitable, which can be summarized as follows: - anti-inflammatory background therapy with chromones and cortisones, mainly for local use, antileukotrienics; - therapy with antihistamines and nasal and bronchodilator decongestants, - specific desensitizing immunotherapy (vaccine).
Antihistamines are the drugs widely used for symptomatic therapy of rhinitis and
conjunctivitis. Compared to old products, which gave drowsiness, dry mucous
membranes, dizziness, tachycardia, those of the new generation have very few
side effects. Recently also antihistamines for local use have been introduced in
the current use, which together with the rapidity of action are good efficacy.
Since antihistamines generally do not improve nasal obstruction, vasoconstrictor
decongestants can be used in association, reducing mucosal congestion. The
latter often have side effects, so their use is indicated for short periods,
above all to promote night rest. Another drug, disodiocromoglycate, has proved
to be effective above all in preventing the symptoms of allergic rhinitis. In pollinosis, it should be administered a few days before the beginning of
pollination, based on the information on the pollen calendar. Cortisones are
very active in the control of symptoms, especially in inhalation (the most
recent can be used with only one daily administration).
As for asthma, it is necessary both the prevention of bronchial spasm crises and their treatment when they are established. The therapeutic measures are based on the elimination and however on the reduction of the effect of the triggering factors, on the control of the rhinitis with an early and complete nasal therapy and on the use of both symptomatic drugs to resolve the bronchial obstruction, and anti-inflammatory drugs for the therapy basically. They are divided into
a) beta 2 stimulating bronchodilators, which release the bronchial
muscles, improving the airway patency, essential drugs in the treatment of the
asthmatic crisis, administered preferably by inhalation through pressurized cans
or inhalable powders. The most important undesirable effects are tremor and
tachycardia. b) theophylline,
c) disodiocromoglicato and nedocromile: anti-inflammatory able to inhibit
immediate and delayed bronco-obstruction induced by allergens, stress and
exposure to cold air, preventing the degranulation of mast cells. The protective
efficacy is reached after a few weeks of therapy and, in pollinosis, such
preparations are indicated for preventive purposes with pre-seasonal use, as
indicated in the rhinitis.
d) corticosteroids: the most effective anti-inflammatory agents in the
treatment of asthma.
e) antileucotrienics, montelukast
The fundamental principle for their use and to use them for a sufficient period, at an appropriate dosage and for the most effective route of administration to guarantee the desired result. In the acute asthmatic attack, intensive short-term treatment with high doses should be implemented, preferably by injection or oral. This therapy should be continued until remission of the asthmatic crisis, with total or partial reversion of the various parameters of respiratory function. Once the acute phase has been overcome, when the dosage reduction of corticosteroids is started generally, these drugs must be administered regularly by inhalation, in sufficiently high doses, and their use must then be prolonged for a long time, even for many months. Their use by inhalation is effective and safe. Side effects, especially in the mouth (thrush), are minimal and can be avoided with simple rinses after each administration. Recently, antileucotrienics have been introduced into therapy, with significant anti-inflammatory activity. They are taken once or twice a day by mouth.
Specific immunotherapy or specific hyposensitization (commonly known as "vaccine") consists of the subcutaneous (or nasal, sublingual or oral) administration of a specific allergen extract, in increasing doses (with possible continuation in constant doses) in order to achieve a reduction in the patient's sensitivity to a certain allergen. The elective indication of vaccination therapy is represented by allergic respiratory diseases by inhalation allergens (allergic rhinitis and / or bronchial asthma), supported by immune reactions mediated by particular antibodies (IgE). The diagnosis must be documented by skin allergy tests and / or laboratory for the demonstration of specific IgE and there must be a close correlation between these data and the clinical history of the allergic subject, which must be of considerable intensity and duration. Another indication to immunotherapy and consisting of hypersensitivity syndromes to hymenoptera poisons (bees, wasps and hornets), in individuals who have experienced generalized reactions to such punctures and in which there is a positivity of skin and / or laboratory tests for these allergens. The latter type of vaccination therapy must be practiced according to particular patterns. In special cases, immunotherapy can be practiced in respiratory allergies caused by mycetes and by animal forphrops or derivatives (grooms, breeders, etc.), in which it is difficult to avoid further exposure of the patient to these allergens.
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