Severe Reaction to Antibiotics: What to Know

A reaction can cause hives, swelling of the lips or face, wheezing, vomiting, dizziness, or collapse. Other serious patterns develop more gradually and may include fever, a tender widespread rash, blisters, peeling, swollen glands, yellowing of the eyes, dark urine, or unusual bruising. These symptoms can overlap with the illness being treated, but a new or worsening change after an antibiotic should be assessed. The responsible drug may be one antibiotic or a combination of medicines, so keep every label and prescription.

If symptoms are mild but new, contact the prescriber promptly before taking the next dose. If there is breathing difficulty, swelling of the mouth or throat, faintness, or collapse, call emergency services and follow the operator's instructions. Do not test the medicine again at home. Record the antibiotic, dose, route, start date, time of the reaction, and any other medicines or supplements. Tell clinicians about previous reactions and ask how the infection will be treated while this medicine is avoided.

Emergency care is needed for airway swelling, breathing trouble, severe dizziness, fainting, confusion, or a rapidly spreading rash. Go urgently for blistering, skin peeling, painful skin, mouth or eye sores, persistent vomiting, or signs of liver or kidney problems such as yellow skin, very dark urine, or markedly reduced urination. Bring the medicine packaging and do not drive if you are faint, breathless, or confused.

Ask which medicine may have caused the reaction, whether it should be documented as an allergy or adverse effect, which alternatives are appropriate, and whether you need an allergy assessment. Ask what written warning to carry and which future symptoms need emergency action.