Drug allergies may cause many different types of symptoms depending on the drug and the degree of exposure to the drug (how often you have taken it).
Symptoms of drug allergies can be mild or life-threatening and appear within 1 to 72 hours. They include:
- Hives or welts, rash, blisters, or eczema. These are the most common symptoms of drug allergies. See a picture of skin reactions caused by drug allergies.
- Coughing, wheezing, runny nose, and difficulty breathing.
- Toxic epidermal necrolysis, which is a serious life-threatening condition that involves blistering, and peeling of the skin.
- Anaphylaxis, which is the most serious reaction. It is life-threatening, and you will need emergency treatment. Symptoms usually appear within 1 hour after you take the medicine and include hives, difficulty breathing, and shock.
A drug allergy can also affect the liver, kidneys, and lymph system. However, you usually do not have any symptoms in this case.
Medicines may also cause:
- Serum sickness. This rare condition usually begins 6 to 21 days after you take the offending medicine. Symptoms include fever, weakness and body aches, joint pain, and skin eruptions, such as hives or a rash.
- Medicine fever. Symptoms include high fever and chills and sometimes a skin rash. When you stop taking the medicine, the fever usually drops within 48 to 72 hours.
- Autoimmune disorders. Drug allergies can cause several autoimmune disorders, such as drug-induced lupus, vasculitis, andmyasthenia gravis, although these are rare. See more information on medicines and lupus.
- Destruction of platelets and red blood cells, resulting in thrombocytopenia and hemolytic anemia, respectively. Symptoms of thrombocytopenia include bruising easily, red spots around the feet and ankles, and nosebleeds. Symptoms of hemolytic anemia include fever, chills, shortness of breath, and a rapid heart rate.