What are the other Names of this Condition? (Also known as/Synonyms)

• Allergy to Drugs
• Allergy to Medication
• Medication Hypersensitivity

What is Drug Allergy? (Definition/Background Information)

• Drug Allergy is a common condition that manifests as an abnormal immune reaction/response to certain drugs that may be administered orally or intravenously. It is observed in both children and adults
• The common allergy-causing medications and drugs include the following:
  • Anticonvulsants
  • Chemotherapy agents
  • Sulfonamide antibiotic drugs
  • Insulin, especially those that are animal-based
  • Contrast dyes (iodine-based) used in radiological studies
  • Non-steroidal anti-inflammatory drugs (NSAIDs) that include aspirin, ibuprofen, etc.
  • Antibiotics belonging to the penicillin family; it is the most common type of Drug Allergy noted
• The medications may be in tablet form, liquid form, or injected form. A Drug Allergy may occur immediately, or within 1-2 hours following exposure to the drug. The condition may be mild, moderate, or severe
• Numerous signs and symptoms of the allergic reaction may be noted including skin rashes and hives, sneezing, breathing difficulties, nausea and vomiting, and indigestion. In some individuals, Drug Allergy may lead to an anaphylactic shock, which is a medical emergency
• Drug Allergies are generally difficult to be diagnosed. A skin-prick test or an oral drug challenge test is normally used in the diagnosis. The diagnosis can also help identify the specific drug (allergen) and group of drugs containing the allergen that are to be avoided
• Anti-allergic medications form the first line of treatment for mild cases of Drug Allergies. Intravenous corticosteroid therapy may be necessary to reduce inflammation. However, in the case of a severe allergic reaction (anaphylaxis), epinephrine injections are recommended
• The prognosis of Drug Allergy may be assessed on a case-by-case basis, but in most cases, it is generally good. Some individuals overcome the condition over time (after many years)

Many individuals sometimes confuse medication side effects with Drug Allergies. It is important to distinguish between a side effect to a drug and a Drug Allergy.

• A side effect is usually caused as an unintended reaction to a drug. Usually, this is not life-threatening and may include nausea, vomiting, and headaches. It is the effect of the drug on the body and an attribute of the drug. Many of the side effects are expected
• Drug Allergies, on the other hand, are caused by the reaction of a body’s immune system to a medication. It can result in potentially life-threatening symptoms. It is the attribute of the specific individual
• Mild Drug Allergy symptoms may include skin rashes and hives, whereas severe symptoms include breathing difficulties, low blood pressure, and palpitations
• Drug side effects may include nausea and vomiting or asthma-like symptoms. But, if skin symptoms, breathing difficulties, gastrointestinal symptoms, etc. are observed following ingestion of the drug, then it is mostly an allergic reaction to the medication
• Side effects of a drug are usually mentioned on the drug label. Complications arising from side effects are usually forewarned to the patients, whereas Drug Allergies are often unexpected
• Sometimes, the signs and symptoms related to drug side effects and Drug Allergies may be overlapping. It is better to always consult a healthcare provider, in case of a confusion between the two

Also, a Drug Allergy should not be confused with drug toxicity, which is caused by an overdose of the medication.

Who gets Drug Allergy? (Age and Sex Distribution)

• Drug Allergies are common hypersensitivity reactions to drugs that occur in both children and adults
• No gender preference is noted and both males and females are affected
• All racial and ethnic groups are equally vulnerable to the condition

What are the Risk Factors for Drug Allergy? (Predisposing Factors)

The common risk factors for Drug Allergy include:

• Use of the drug in pill or liquid form
• Any family history of Drug Allergy
• Infants and young growing children may have a higher risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Drug Allergy? (Etiology)

An allergic reaction occurs in an individual with Drug Allergy, because the immune system recognizes certain substances/components in the drug as being dangerous and harmful to the body.

• Intake of the drug component results in the production of antibodies, specifically immunoglobulin E (IgE). The next time the individual is exposed to the particular substance, the antibodies that are circulating in blood causes an antibody-antigen reaction
• This results in the production of histamine and other chemical messengers, which cause the symptoms seen during an allergic reaction
• The quantity of medicine that triggers an allergy may not be significantly large. Sometimes, consuming tiny amounts of the allergen is sufficient to trigger the condition

In some cases, a severe allergic reaction termed as anaphylaxis may occur, which is a medical emergency that requires immediate medical attention.

What are the Signs and Symptoms of Drug Allergy?

The signs and symptoms of Drug Allergy may start to appear within a few minutes, to a couple of hours, after the individual has been administered the medicine. In some, the symptoms are mild, while in others they are severe. It also depends on the specific drug type causing the condition. A severe allergic reaction is a medical emergency.

The common signs and symptoms of Drug Allergy may include:

• Itching of skin and eyes
• Minor skin rashes are seen in many cases; in others, it may result in urticaria (hives) and/or angioedema
• Hoarseness
• Shortness of breath (trouble breathing), wheezing, asthma-like symptoms
• Runny or stuffy nose
• Watery eyes, redness, and irritation
• Increase in pulse rate, palpitations
• Low blood pressure (hypotension)
• Nausea and vomiting
• Diarrhea
• Abdominal cramps and pain
• Confusion and dizziness
• Loss of consciousness, fainting

If there is a delayed reaction to drugs, it may present the following symptoms:

• Fever and chills
• Joint aches
• Formation of skin blisters

Generally, not all episodes of allergy will be of the same severity. In some individuals, the most severe symptom caused by certain Drug Allergies is anaphylaxis.

• Anaphylaxis (sometimes called an anaphylactic shock) is a life-threatening, whole-body allergic reaction
• During anaphylaxis, tissues in various body parts release histamine and other messenger chemicals, which causes swelling of the throat and other symptoms
• Swelling of the throat is especially dangerous as this can cause shortness of breath. If the swelling is not reduced soon, then there is a possibility that the individual could die from a lack of sufficient oxygen
• It can also result in a bluish skin, weak pulse, and decreased blood pressure (hypotension)

How is Drug Allergy Diagnosed?

In general, it is difficult to diagnose the condition, unless the allergic symptoms are noted. The diagnosis of Drug Allergy may involve the following:

• Physical examination, assessment of symptoms, and medical history evaluation (history of allergies in the family)
• Evaluation of complete list of medications being taken by the individual

The tests that are usually conducted to diagnose Drug Allergy include:

• Oral drug challenge testing; when the individual is administered the allergens in a controlled manner to check for symptoms that develop
• Radioallergosorbent (RAS) test; to determine the specific allergy-causing substance
• Skin-prick test: This is a reliable test only for penicillin, and not for many other drugs
  • For this test, tiny amounts of certain substances are injected right underneath the skin (forearm, upper arm, or back)
  • After 15-20 minutes, if the spot where the chemical was injected swells, or if there is redness noticed, then this indicates that the individual may be allergic to the substance
• Blood test to detect antibodies (IgE antibody test)

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Drug Allergy?

The complication of Drug Allergy is associated with the allergic reaction itself and it depends on the severity of the reaction. It may include:

• Anaphylactic shock/reaction that may be life-threatening
• If multiple organs are involved, it can cause a condition called drug rash with eosinophilia and systemic symptoms (DRESS syndrome)
• Having allergy to one type of a drug can make the individual prone to other Drug Allergy types
• In severe reactions, a tracheostomy may have to be performed during an emergency situation 

How is Drug Allergy Treated?

The treatment of Drug Allergy may be undertaken in the following manner:

• Avoiding drugs (and all related drugs) that contain the specific allergy-inducing component
• Anti-allergic medication for mild reactions; antihistamine therapy, that is prescribed by the allergy physician
• Symptomatic treatment; use of decongestants, especially for nose block including steroid sprays
• Intravenous corticosteroid therapy to reduce inflammation, or administration of NSAIDs (if the individual is not allergic to these medications)
• In the case of anaphylaxis (severe allergic reaction), epinephrine or adrenaline is immediately administered
• Breathing support as necessary, control asthma symptoms and low blood pressure
• Bronchodilators for respiratory conditions such as asthma, wheezing, etc.

Drug desensitization therapy to make the individual get used to the drug. This is undertaken when no suitable alternative medication is available to treat the condition. However, this does not ensure that the body has completely got used to the allergic drug.

How can Drug Allergy be Prevented?

It may not be possible to completely prevent Drug Allergy; however, the following factors may be considered:

• Immediately inform the healthcare provider if you experience any side effects to a drug or other symptoms; this may help the physician evaluate for any associated Drug Allergy
• Studies have shown that breastfeeding children for 4-6 months or over, can help build their body immunity and make them less prone to allergies
• Appropriate maternal diet during pregnancy can help build stronger resistance (against allergies) in children
• Use alternative medications, where possible

In case the child or adult is susceptible to an anaphylactic shock (high-risk individuals) from Drug Allergy, the following should be considered:

• Being watchful of triggers and avoiding them
• Wearing medical alert information bracelets or suitable devices
• Carry auto-injector epinephrine or adrenaline medications such as EpiPen, Anapen, or Twinject. Since the condition may recur, it is advised to carry 2 doses (2 pens)
• Supervise children on how to self-administer the injection, if required
• If child is prone to anaphylactic reaction, then information (preferably written instructions) should be given to day care, school authorities accordingly
• Adults should inform their spouses, colleagues, and friends, about the condition, in case of a future emergency

What is the Prognosis of Drug Allergy? (Outcomes/Resolutions)

The prognosis of Drug Allergy depends on the severity of the signs and symptoms. It is generally assessed on a case-by-case basis.

• In many cases, the prognosis is good with adequate treatment. Some individuals overcome the allergy over time (after many years), while some may have it for the rest of their lives
• In some cases, the allergic reaction may be severe, causing anaphylaxis. This is a medical emergency that can lead to a respiratory failure. It requires an immediate treatment of the condition. In such cases, the prognosis is guarded and it depends on whether immediate medical assistance is provided

Additional and Relevant Useful Information for Drug Allergy:

Please visit our Allergy Health Center for more physician-approved health information:

http://www.dovemed.com/health-topics/allergy-center/