Drug allergies can cause a variety of symptoms and even life-threatening conditions. In drug allergies, individuals show true allergic reactions to drug ingredients. Itchy skin rashes with wheals usually appear within minutes to a few hours. Sometimes there are other symptoms such as swelling, restlessness and itching in the mouth. Occasionally, a dangerous state of shock develops. Alternatively, a skin rash with nodules can form after a delay, i.e. after six hours at the earliest. Other forms are rare.
Diagnosing drug allergies is difficult. The symptoms can be very different and similar to those of other drug intolerances. Tests often provide unreliable results. Unpleasant phenomena in connection with medication are usually not allergies anyway, but undesirable effects - i.e. side effects or interactions.
If a drug allergy has been diagnosed with certainty, those affected should omit the drug in question. In some cases, it can be replaced by others or temporarily continue to be used with precautionary measures. Medication can help with allergy symptoms.
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| symptoms of drug allergy |
Causes, risk factors and frequency
In principle, anyone can develop allergies and any medication can trigger an allergic reaction. But it only affects some people and affects only some medications. Experts only have a rudimentary understanding of why this is so. Accordingly, they assume that the people affected have an unfavorable hereditary predisposition. Before the allergy occurs, the immune system becomes sensitized. But not every sensitization is followed by an allergy.
Risk factors for developing a drug allergy are:
- Old age: Most new cases occur in middle to old adulthood.
- Female gender: Females are affected more often than males.
- Family predisposition: Anyone who has close relatives with drug allergies is at a higher risk themselves.
- Stress and disorders of the immune system: Infections, cancer, weakness of the immune system and similar diseases increase the risk if medication is used at the same time as usual.
- Disorders of the degrading organs: The liver and kidneys process and excrete the vast majority of active pharmaceutical ingredients and their degradation products. If the function of these organs is disturbed, the substances remain in the body longer. This obviously increases the risk of allergies.
Intolerances are known for many drugs. Surveys show, however, that some drugs lead to allergies and intolerances/pseudo-allergies more often than others. These include, for example, these drug groups and their active ingredients or additives:
- Antibiotics (e.g. penicillins, cephalosporins, sulfonamides, nitrofurantoin)
- Medications for epilepsy (e.g. carbamazepine, mesuximide, phenytoin)
- Painkillers/rheumatism (e.g. acetylsalicylic acid (ASA), ibuprofen)
- Blood pressure lowering agents such as ACE inhibitors (e.g. Captopril)
- Local anesthetics (local anesthetics)
- X-ray contrast media
- Anesthetics
- Drugs for cancer chemotherapy
The type of application influences how often allergic reactions occur and how severe the symptoms become. On average, the frequency and severity are higher when drugs enter the body directly, i.e. by infusion or injection. The risk of strong reactions with infusions via the vein is particularly high. There is a low risk of allergic reactions when taking tablets, drops and the like by mouth. On the other hand, side effects and interactions are common here. Agents that get to the skin locally most commonly cause sensitization and often contact allergies, but these are localized. Irregular use with breaks is more likely to result in allergic reactions than regular use. It is also disadvantageous if patients have to significantly increase the dose of a drug or if they have to use many drugs at the same time.
It is difficult to pinpoint the frequency of drug allergies. Statistics often only list drug intolerances overall, because tests to differentiate the forms often give unsatisfactory results. Even the figures for intolerance differ significantly. According to information from four international medical professional organizations, more than 7% of the population are affected by intolerances. Allergies and intolerances/pseudo-allergies are said to affect one in 100 people. According to other experts, one in four people (25%) will suffer from drug tolerance at some point in their lives. The frequency of drug allergies is said to be 4 to 5%. In our hospitals, two to three out of 100 patients with skin changes react to medication. A fifth of these develop life-threatening symptoms.
Symptoms
Does your skin become red and bumpy fairly soon after using a certain medication?
Do you also get other symptoms such as burning and itching around the eyes or swelling in parts of the face?
Do you often get a rash that resembles measles and has pustules days after using a remedy?
Both the early rash with wheals and the late rash with pustules are typical allergy symptoms. But it is hardly possible to draw conclusions about a drug allergy from such signs. Drugs can cause many very similar and sometimes very different symptoms in different ways, so-called drug intolerance (see below). In the vast majority of cases, when people complain about unpleasant symptoms in connection with medication, it is a question of side effects or interactions with other drugs.
Those affected should have any real or suspected drug intolerance clarified. This applies to children and adults. Meaningful advice and assessment of the risks can only take place when the triggers are known and, if possible, their mode of action.
Shapes and signs
According to the way in which allergies develop in the immune system, experts distinguish between several types. Drug allergies can be type I allergies or immediate-type allergies. IgE-type antibodies mediate the allergic reaction. However, drug allergies are usually regarded as typical examples of type IV allergies, which are also called late or delayed type. Antibodies play no role here. The immune reaction runs through certain, specialized white blood cells, through sensitized T-lymphocytes. Experts also speak of a cell-mediated immune response.
Type I/immediate type drug allergies often have the following symptoms:
- Red and warm skin
- Rash with raised wheals (hives/urticaria)
- Itching
- Swelling
- Allergic rhinitis, allergic asthma
- Red, itchy and burning eyes (allergic conjunctivitis)
- Mild physical symptoms such as restlessness and headaches
Severe courses are shown by other symptoms in addition to the skin. In the worst case, a life-threatening anaphylactic shock can develop. Early warning signals can already be feelings of heat and itching or burning in the mouth and throat. These signs often disappear quickly. At the same time or shortly thereafter, swallowing difficulties and increased mucus formation usually occur. The airways narrow, breathing becomes difficult. Nausea, vomiting, spasms in the gastrointestinal tract and diarrhea may appear. In addition, the blood pressure drops sharply. The pulse is usually no longer palpable. The skin becomes pale, bluish in color and cool. Cold sweat breaks out. The heart increases its beating rate up to palpitations. Without proper treatment, cardiac arrest occurs, the circulatory system collapses, and death occurs. If an anaphylactic shock is imminent, not all of the symptoms mentioned must always appear. Drug allergies are the second most common cause of anaphylactic shock in adults, after insect venom allergies.
You should call an ambulance at the latest if you experience symptoms such as sweating, bluish skin or breathing difficulties. These signs strongly indicate that a shock is imminent. The condition of those affected can deteriorate dramatically very quickly! When in doubt, it is not a mistake to contact an emergency service even if you have earlier symptoms that may indicate anaphylactic shock.
Angioedema or Quincke's edema can occur, usually with the hives. Their mechanism of formation is the same. In angioedema, however, deeper layers of the skin are affected, including connective tissue and mucosal tissue. Severe swelling occurs very quickly, mainly on the face, e.g. on the eyelids, lips, chin and cheeks. Tissue around the genitals can also swell. If the airways are affected, there is often a risk of suffocation. The edema is treated with antihistamines, glucocorticoids (e.g. cortisone) and sometimes with adrenaline if the patient's respiratory tract is known to react strongly to the allergens. If necessary, artificial respiration or a tracheotomy must take place. In general, the edema resolves within hours to days without any consequences.
In the case of type IV/delayed type drug allergies, symptoms often appear after several days, rarely after just a few hours. A skin rash develops, the appearance of which is often reminiscent of measles or scarlet fever (technical term: drug eruption). Small spots or pustules often form first, which then flow together to form larger areas. The skin condition is mostly harmless and goes away on its own without leaving any traces. Severe courses are considered complications and are rare.
Drug intolerance
Drugs, i.e. their active ingredients and sometimes also additives, can bring with them a wide range of symptoms. Experts summarize them as drug intolerances. There are three different forms, they differ in the processes that lead to symptoms. In the case of side effects and interactions, the severity of the symptoms depends on the dose of the drug. This is not the case with allergies and intolerances, which are also called pseudoallergies. They are caused by processes in the immune system. The symptoms can differ, but can also be similar in some cases.
Side effects and interactions with other medications are by far the most common unpleasant symptoms after using medication. According to studies, at least three out of four people who complain of medication-related complaints suffer from them. In some studies, the proportion was even 80 to 90%. The nature of the possible complaints should be listed in the package leaflet. They are part of the drug effect, an undesirable effect. Accordingly, the severity of the symptoms increases with the dose of the active ingredient. The immune system is not involved.
Depending on the study, drug allergies are present in one to three out of ten people who complain of symptoms in connection with the use of drugs. The symptoms come about because the immune system reacts allergically to pharmaceutical active ingredients or additives in the medication. There are two forms with different backgrounds: In type I allergies, immunoglobulins of the IgE type mediate the immune reaction, in type IV allergies, certain immune cells, the T-lymphocytes, are responsible for this.
Drug intolerance or pseudoallergies are considered to be widespread. The immune system is involved, but no allergic processes take place there. The immune system does not produce any immunoglobulins in order to specifically attack the triggers. The triggering drug substances themselves unspecifically activate specific cells that also play a role in real allergic reactions. Therefore, the symptoms of an intolerance/pseudoallergy and those of a type I allergy are similar.
In addition, contact allergies caused by drugs that come into contact with the skin are very common. In the narrower sense, however, they belong neither to drug allergies nor to intolerances. Contact allergy symptoms are limited to the skin. They can be very uncomfortable but are not dangerous.
Treatment
Before treatment, it should be clear that it is a real allergy and not a side effect or an intolerance/pseudo-allergy. Drug allergies are difficult to detect. A survey can provide initial clues. For example, if a patient has been taking a certain drug regularly for years but is only now developing symptoms, an allergy is very unlikely. The periods, the intervals between applications and the nature of the symptoms must be appropriate. Anyone who has a suspicion can support the diagnosis by noting as many details as possible.
If it becomes clear that it is an allergy, investigations follow. Some specific IgE antibodies can be found in blood tests. However, there are no tests for some active pharmaceutical ingredients that can cause allergies. Sometimes it is not the active ingredients that cause the reactions, but additives or the substances that our body makes from the active ingredients. Blood tests alone do not allow reliable statements. Skin tests such as prick, epicutaneous and intracutaneous tests are considered more important. However, they often remain without useful results. Almost only highly allergic patients, which are very rare, react in the skin prick test. Attempts to detect sensitization or allergy with these tests are usually unsuccessful.
The last way to trace symptoms back to a specific remedy is to carry out complex provocation tests. Patients receive the drug that is probably causing them problems in increasing doses. If they then develop symptoms of an immediate or delayed type reaction, they will receive a corresponding allergy card. The remedy in question should be avoided from now on. Because there is a risk of developing dangerous symptoms, the test usually takes place in the hospital and is monitored. With the result, allergies and intolerances/pseudo-allergies cannot be differentiated.
Avoid and Replace
The options for treating drug allergies are limited. Basically, the therapy boils down to replacing the drug in question with another, if possible, or doing without it altogether.
- Waiver: The best therapy is to completely omit the drug that has been proven to trigger the severe allergic symptoms. Of course, this is only possible if the medicinal product is not absolutely necessary from a medical point of view. However, this is rather the exception. Patients who only experience mild allergic symptoms can often use the appropriate remedies again on certain occasions after professional advice.
- Substitution: In some cases, it is possible to substitute a remedy or entire procedure for another with equivalent medical effects. For example, an X-ray contrast medium is unnecessary if patients receive magnetic resonance imaging/MRI instead of computed tomography. Those affected should seek professional advice on a case-by-case basis.
- Medication for mild symptoms: Skin rashes caused by drug allergies often heal faster with topical creams containing glucocorticoids (e.g. cortisone). Cooling gels with active ingredients from the antihistamine family can help against the itching.
- Allergy passport or identity card: Those affected should receive and carry a passport or identity card that lists the substances to which allergies exist. In an emergency and if they are unconscious, they do not receive any risky medication or the doctors can prepare for the assignment accordingly.
- Preventive medications and procedures: Some medications can be almost essential for certain purposes, such as X-ray contrast media for some X-ray procedures. If an intervention is necessary despite an allergy, doctors can prescribe medication such as glucocorticoids (e.g. cortisone) and antihistamines to alleviate allergic reactions. However, to be on the safe side, an emergency preparedness must be in place. In some cases, it is also possible to reduce the sensitivity of those affected (technical term: tolerance induction). The parties involved should carefully weigh up all the advantages and disadvantages, alternatives and risks together.
- Severe symptoms, anaphylaxis: Symptoms such as sweating, bluish discoloration of the skin and difficulty breathing pose a risk of developing anaphylactic shock, which can be life-threatening. The condition of those affected can deteriorate very quickly. If in doubt, an ambulance should always be called or the symptoms treated appropriately with an emergency kit.
A causal treatment, the so-called specific immunotherapy (SIT, also hyposensitization), is unfortunately not possible in the case of real drug allergies. In the case of intolerances/pseudoallergies, individual cases are described in which SIT was able to eliminate the problems.