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Drug Allergies
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The term drug allergy is often misused and some people do not take specific drugs because they fear allergy. Sometimes such drugs can be crucial for health (antibiotics) and unjustified avoidance thereof can have serious consequences for the patient. Anybody can experience some unwanted reactions to drugs caused by drug overdosing, drug side-effects or interaction of different drugs. The other group of reaction to drugs includes real reactions triggered by hypersensitivity. Such reactions do not depend on the stated features and are manifested only in hypersensitive individuals and can be the consequence of e.g. drug intolerance, idiosyncrasy and drug immunological reaction (drug allergy). From the above mentioned it is obvious that only a fraction of reactions manifested upon consumption of a drug can be attributable to a drug allergy. Hypersensitive reactions are significantly less frequent that the reactions belonging to the first group and happen only in 6-10% of all unwanted reactions to drugs. The risk of a true drug allergy is 1-3%. Allergic reactions to drugs are immunological reactions that are manifested only in a small segment of people that have previously taken a specific drug.
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What drugs most frequently trigger allergic reactions?
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Any drug can cause allergic reactions. The manner of application, duration of treatment and frequency of drug application all contribute to development of hypersensitivity to drugs. Drug sensitivization occurs more frequently after skin or mucous membrane drug application than after oral drug application. Anaphylactic reaction is more frequent after injection of a drug (penicillin). Long-term application of high dosages and frequent application of the same drug can also increase the danger of allergic reactions to the drug. Drug allergies are less frequent in nursing infants and small children than in adults. Interestingly enough, skin drug allergies are much more frequent in women, and individuals allergic to one specific drug are 15 times more likely to develop an allergy to some other drug.
Drugs most frequently causing allergic reactions are: aspirin and similar drugs proscribed against pains or high temperature (the so-called non-steroidal anti-inflammatory drugs - NSAID), antibiotics (penicillins, cephalosporins, carbapenems), sulfonamides, antituberculous drugs, nitrofurantoin, anticonvulsants, anesthetics, etc.)
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How to identify drug allergy
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Skin symptoms are most frequent. Urticaria and/or angioedema can occur shortly after consumption of a drug. This manifestations usually diminish upon termination of a drug therapy. Frequent manifestations are rashes, tiny morbiliform rash (similar to measles) or maculopapular (bigger, blotchy, above the skin level). Rashes are usually symmetric and tend to blend and do not appear on the palms and soles. In children, such changes can be misdiagnosed with typical children virus diseases (chickenpox and measles). In some patients, drug allergy is manifested only after sun exposure and such a symptom is called photoallergic effect. In some casee, reaction occurs after skin application of the drug and is referred to as contact allergic dermatitis.
Beside skin, drug allergy can affect other organic systems: respiratory (rhinitis or asthma symptoms, cough, pulmonary infiltrates with eosinophilia), digestive (symptoms of gastritis, enteritis, hepatitis), urinary (interstitial nephritis, glomerulonephritis), nervous (epileptic spasms, neuritis) and circulatory (eosinophilia, thrombocytopenia, hemolytic anemia). Reactions to drugs can be manifested by simultaneous symptoms of several organic systems (serum disease and hypersensitivity syndrome). The most serious reactions to drugs are anaphylactic and anaphylactoid shock.
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How to diagnose drug allergy
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During a diagnostic procedure for each patient suspected of having allergic reaction to drugs, it is necessary to identify the exact name of the drug, the time when the first symptoms have appeared, types of the drug, repeated consumption of the same drug or drugs of the same group, sensitivization to other drugs, family medical history, etc. Detailed anamnestic data are sometimes sufficient to reach an exact diagnosis for a specific drug allergy. Additional tests are also useful even though they are not abundant nor reliable. Specific IgE antibodies can be identified only for a small number of drugs. Sometimes skin tests are applied, but they are not standardized enough and are potentially harmful. The most important tests for diagnosing existence or absence of a drug allergy are provocative (challenge) tests administered in specialized institutions under strict supervision and in controlled conditions upon receiving approval of the patients or parents. This test consist of administering gradually increasing dosage of a specific drug up to the therapeutic dosage. Beside diagnostics, this method can be used therapeutically in view of drug hyposensitization (aspirin), as in case of asthma and rhinitis.
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How to react in case of drug allergy
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Therapy depends on the type of an allergic reaction to a specific drug. Each patient who has experienced systemic (general) reaction must be taken to the hospital or at least monitored during the next 12-24 hours. It is crucial to stop taking the drug and prohibit consumption of the drugs belonging to the same group. If the allergy is manifested by a skin rash and mild urticaria, it is sufficient to take antihistamine tablets. Every more serious allergy reaction to a drug demands a medical checkup and monitoring. The patient is regarded to be allergic to that drug until that allergy is excluded by a more objective testing.
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Vaccine allergies
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Beside active components (the ones one is vaccinated for), vaccines also contain potentially harmful, allergic components. Some of these additives are used for vaccine maintenance (preservatives) and some represent unavoidable pollutants (antibiotics and proteins of the biologic system in which the immunogen was produced). Therefore, if vaccination is followed by unwanted reactions, these are caused by hypersensitivity to any of the stated components. Allergic reactions to the active component of vaccination (immunogen) are extremely rare. The most frequent are local reactions upon vaccination (swelling and redness) and a rise of temperature. Allergic reactions are most frequently triggered by non-active components, antibiotic added to the biologic system in which immunogen was produced (neomycin, streptomycin) or proteins of chicken embryos used for producing certain virus vaccines.
It is a known fact that individuals that have experienced anaphylactic reaction to eggs can develop allergic reactions to vaccines against chickenpox, measles and mumps. In Croatia, there is a vaccine containing solely mumps virus produced on the chicken embryo and vaccination by this vaccine is not contraindicated even in allergic patients. Children with serious forms of atopic dermatitis should also be vaccinated against stated diseases. In some children that have experienced systematic (general) allergic reaction following vaccination with this vaccine (urticaria, asthma, anaphylactic shock), it has been proved that the allergy has been triggered by an emulsion frequently used as a stabilizer.
Side-effects during vaccination against diphtheria, tetanus and pertussis, the so-called DTP vaccines, (encephalopathy, collapse, convulsion, hyperpyrexia) are not caused by allergic reactions but are connected to the component against pertussis. Beside progressive neurological disease, there is no absolute prohibition of this vaccine. In such a case, the so-called acellular vaccine is used for pertussis. In exceptionally rare cases (1: million), after DTP vaccination certain allergic reaction of the early type (anaphylactic shock, urticaria) and serum disease can occur. More frequent are allergic reactions to tetanus and diphtheria toxoid especially if the vaccine is old or inappropriately maintained. The frequency of reactions increases with the number of revaccinations and the level of previously achieved level of antibodies. Thus, it is important to know when was the last time the patient was vaccinated against tetanus.
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How schools handle food allergy?
A survey of nurses in elementary and middle schools in the U.S. found that food allergy action plans for students with food allergies are used inconsistently.
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