Drug Information Q&A Q12. What is drug allergy?
Answer
When a drug that has entered the body binds to a protein in the blood and antibodies against it are formed in the body, a specific reaction may occur the next time the same drug is given to the patient. This is called drug allergy and is one of the symptoms of drug hypersensitivity.
Explanation
Humans have an immune system that distinguishes between our own cells and foreign substances that have invaded from the outside and tries to eliminate them.
However, when this immune function overreacts, it sometimes causes symptoms that are harmful to the human body. This is called allergy. Allergens include mites, pollen, pet hair, food, and other substances, but drugs can also be allergens for some people.
Allergies such as hay fever and atopic dermatitis are currently a major problem in Japan.
It is said that 30% of the population suffers from hay fever, and when asthma caused by dust mites and house dust and skin diseases caused by food and chemical substances are added, the number of allergy sufferers is said to be as high as one out of two. The modern era can be called the "allergy era.
Allergy is a general term for an immune reaction (neutralizing action) that occurs when an allergen enters the body and works against the body. Pharmaceuticals can also be allergens, depending on a person's constitution.
In the past, penicillin shock was noted as a typical example of drug-induced allergy. Penicillin, which had shown miraculous efficacy against bacterial infections, caused allergic reactions and even deaths, and this became a major problem. Since then, improvements in the purity of penicillin preparations have reduced the frequency of shocks, but antibacterial drugs and antipyretic analgesics are still known as drugs that can cause allergic reactions.
Although there are cases of drug-related allergies, such as sudden shock caused by injections, most cases start with mild symptoms such as eczema, itching, dizziness, or ringing in the ears that occur after continuous use of the drug. Some symptoms may appear mild at first but become severe, so it is important to consult a doctor or pharmacist immediately. If you stop using the medication at that point, the allergy will almost always subside.
Another important thing is to record the name of the drug that caused the allergy, even if it was only a mild case, in your medication diary, and be sure to tell your doctor the next time you visit the hospital so that he or she will not prescribe that drug again.
Also, since allergies tend to occur in people of the same constitution, it is important to tell your doctor if you or a family member is allergic to any of the medicines.
Chart/Column
12｜Example of the entry fields for allergy history (with or without allergy) in the Medication Record Book
When prescribing a medication, the doctor/pharmacist will refer to the information in the allergy history (with or without) section of your "Medication Handbook. Make it a habit to fill out the form without fail so that you do not forget to do so.
MINI Column Penicillin Shock
Penicillin was said to be a magic medicine because of its effectiveness against infectious diseases, but the "penicillin shock" incident taught us that even penicillin should not be overconfident.
In 1956, Professor Asao Otaka of the University of Tokyo Faculty of Law died of anaphylactic shock caused by penicillin injection during treatment of a cavity. The cause was an allergic reaction accompanied by severe shock. The death of a prominent figure at the time from an unimaginable cause caused a social problem.
At the time of Professor Otaka's death, penicillin products were only about 75% pure, even at their highest purity, and were thought to contain many impurities. The purity of penicillin products manufactured today is more than 99%, and the frequency of shock is low. However, since allergic reactions vary with the individual's constitution, it is important to keep a note of any special reactions to drugs in the past.
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