Side effects can occur with any medication. Among these side effects, reactions caused by an excessive immune response to a specific drug are referred to as drug allergies.

Symptoms range from mild reactions that improve after discontinuation of the causative drug to severe conditions that affect the entire body.
Skin manifestations are common and are referred to as drug eruptions. Other possible symptoms include respiratory disorders (such as asthma or pneumonia), liver dysfunction, kidney dysfunction, and blood disorders.

The following severe drug allergies are rare and occur infrequently. However, if they are overlooked or left untreated, they may become life-threatening. Therefore, particular attention is required for anaphylaxis and severe drug eruptions, such as Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug-induced hypersensitivity syndrome (DIHS).

Anaphylaxis is a hypersensitivity reaction in which symptoms involving multiple organs—such as skin symptoms (e.g., hives), gastrointestinal symptoms (e.g., abdominal pain or vomiting), and respiratory symptoms (e.g., shortness of breath)—appear simultaneously or rapidly. Certain medications may trigger anaphylaxis.

Medications associated with anaphylaxis include contrast agents, blood products, antibiotics, anticancer drugs, antipyretic and analgesic agents, and over-the-counter (OTC) medications.

If you experience symptoms such as skin redness, hives, itching in the throat, nausea, sneezing, coughing, wheezing, hoarseness, shortness of breath, palpitations, or dizziness, please seek medical attention immediately.
If anaphylaxis is suspected, call emergency services right away.

(Stevens–Johnson Syndrome, Toxic Epidermal Necrolysis, Drug-Induced Hypersensitivity Syndrome)

In rare cases, severe skin reactions may occur after taking certain medications. If you experience any of the following symptoms, please seek medical attention immediately.

SJS has been reported with antibiotics, antipyretic analgesics, and anticonvulsants, and may also occur with OTC medications such as cold remedies.

Symptoms include:

• High fever (38°C / 100.4° F or higher)
• Redness of the eyes
• Eye discharge
• Swelling of the eyelids
• Difficulty opening the eyes
• Erosions or sores on the lips or genital area
• Pain during urination or bowel movements
• Sore throat
• Widespread redness of the skin

If these symptoms persist or worsen rapidly, do not ignore them and contact your doctor or pharmacist immediately.

TEN has been reported with antibiotics, antipyretic analgesics, anticonvulsants, and OTC medications such as cold remedies.

Symptoms include:

• High fever (38°C / 100.4° F or higher)
• Redness of the eyes
• Erosions of the lips
• Sore throat
• Widespread redness of the skin

If these symptoms persist or worsen rapidly, seek medical attention immediately.

DIHS has been reported with antiepileptic drugs, medications for gout, sulfonamides, and OTC medications such as cold remedies.

Symptoms include:

• Widespread skin redness
• High fever (38°C / 100.4° F or higher)
• Sore throat
• General fatigue
• Loss of appetite
• Swollen lymph nodes

If you notice these symptoms, do not delay and contact your doctor or pharmacist immediately.

Do you carry a Medication Notebook?
This notebook includes pages for recording adverse drug reactions, allergy history (to medications or foods), and past medical history.

If you experience an allergic reaction or side effect, be sure to record it.
When visiting a medical institution, please present your Medication Notebook to your doctor or pharmacist. Reviewing this information helps prevent recurrence of drug allergies and ensures appropriate medical care.