A drug allergy is a hypersensitivity of a person's immune system to a particular drug he has taken, according to Penn State University. Anyone can develop a drug allergy to any medication. It is impossible to determine which drugs a person is allergic to until he takes them. A drug allergy often does not occur the first time someone takes a medication, according to MedlinePlus. If an allergy develops to the medication, the symptoms will usually occur after later doses because the immune system has identified the drug as a harmful substance.
Cause
After ingesting a medication, the body may categorize it as a dangerous substance, building up a resistance with antibodies. The next time a user takes the drug, the immune system responds by attacking the drug, causing histamine to be released throughout the body. Histamine is the chemical in the body that produces most allergy symptoms. The most common drugs that cause drug allergy symptoms are penicillin and other antibiotic drugs, according to MedlinePlus.
Signs
The most common signs of a drug allergy occur directly after taking the drug. Some signs of a drug allergy may be swollen lips and face, hives or a rash on the face, according to the University of Maryland Medical Center. If the reaction results in anaphylactic shock, signs may include wheezing and a drop in blood pressure. Contact a doctor immediately if these signs appear.
Symptoms
The most obvious symptoms of a drug allergy will be noticed on the skin, around the face, according to MedlinePlus. The skin and eyes will become very itchy, followed by an unexplained skin rash. Hives can develop as a symptom of a drug allergy, along with wheezing and swelling of the face, tongue or lips, according to the University of Maryland Medical Center. If these symptoms develop and someone has not taken a drug, they are the result of a different type of allergic reaction.
Severe Symptoms
According to Penn State University, a drug allergy can cause someone to experience anaphylactic shock. This is a rare condition where the entire body has an allergic reaction, causing physical shock. Anaphylactic shock symptoms are confusion, chest tightness, dizziness, fainting, hives, vomiting and nausea, increased heart rate, wheezing and diarrhea. This is a life-threatening condition and needs immediate medical attention. Call 911 if these symptoms develop.
Considerations
If a patient experiences any side effects from a medication, she should discuss it with her doctor. All drugs being used need to be disclosed to the doctor, including over-the-counter drugs.
