Drug Reactions

On this page

Basics

• Summary
• Start Here
• Diagnosis and Tests

Learn More

• Related Issues
• Specifics
• Genetics

See, Play and Learn

• Images
• Videos and Tutorials

Research

• Clinical Trials
• Journal Articles

Resources

• Reference Desk
• Find an Expert

For You

• Children
• Older Adults
• Patient Handouts

Summary

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions.

One problem is interactions, which may occur between

• Two drugs, such as aspirin and blood thinners
• Drugs and food, such as statins and grapefruit
• Drugs and supplements, such as ginkgo and blood thinners
• Drugs and diseases, such as aspirin and peptic ulcers

Interactions can change the actions of one or both drugs. The drugs might not work, or you could get side effects.

Side effects are unwanted effects caused by the drugs. Most are mild, such as a stomach aches or drowsiness, and go away after you stop taking the drug. Others can be more serious.

Drug allergies are another type of reaction. They can be mild or life-threatening. Skin reactions, such as hives and rashes, are the most common type. Anaphylaxis, a serious allergic reaction, is more rare.

When you start a new prescription or over-the-counter medication, make sure you understand how to take it correctly. Know which other medications and foods you need to avoid. Ask your health care provider or pharmacist if you have questions.

Start Here

• Drug Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish
• Drug Interactions: What You Should Know (Food and Drug Administration) Also in Spanish
• Drug Reactions (American Academy of Family Physicians) Also in Spanish
• Medication/Drug Allergy (National Jewish Health)
• Medications and Drug Allergic Reactions (American Academy of Allergy, Asthma, and Immunology) Also in Spanish

Diagnosis and Tests

• Anaphylaxis (American Academy of Allergy, Asthma, and Immunology) Also in Spanish
• Anaphylaxis-Like Reactions (National Jewish Health)
• Pharmacogenetic Tests (National Library of Medicine) Also in Spanish
• Therapeutic Drug Monitoring (National Library of Medicine) Also in Spanish

Related Issues

• Drug-Food Interactions (American Academy of Family Physicians) Also in Spanish
• Harmful Interactions: Mixing Alcohol with Medicines (National Institute on Alcohol Abuse and Alcoholism) Also in Spanish
• Index to Drug-Specific Information (Food and Drug Administration)
• Medication Errors: Cut Your Risk with These Tips (Mayo Foundation for Medical Education and Research) Also in Spanish
• Medication Interactions: Food, Supplements and Other Drugs (American Heart Association)
• OTC Medicines: Know Your Risks, and Reduce Them (American Academy of Family Physicians) Also in Spanish

Specifics

• Aspirin Allergy: What Are the Symptoms? (Mayo Foundation for Medical Education and Research) Also in Spanish
• Examples of Dietary Supplement Interactions (American Academy of Family Physicians) Also in Spanish
• Grapefruit Juice and Some Drugs Don't Mix (Food and Drug Administration) Also in Spanish
• Neuroleptic Malignant Syndrome (National Institute of Neurological Disorders and Stroke)
• Penicillin Allergy (Mayo Foundation for Medical Education and Research) Also in Spanish
• Sulfa Allergy: Which Medications Should I Avoid? (Mayo Foundation for Medical Education and Research) Also in Spanish

Genetics

• Genetics Home Reference: Stevens-Johnson syndrome/toxic epidermal necrolysis (National Library of Medicine)
• Genetics Home Reference: thiopurine S-methyltransferase deficiency (National Library of Medicine)

Images

• Drug Eruption (Logical Images)

Videos and Tutorials

• Don't Take This with That! (Food and Drug Administration)

Clinical Trials

• ClinicalTrials.gov: Drug Hypersensitivity (National Institutes of Health)
• ClinicalTrials.gov: Drug Interactions (National Institutes of Health)
• ClinicalTrials.gov: Drug-Related Side Effects and Adverse Reactions (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

• Article: Drug-related Halitosis: A Systematic Review.
• Article: Metabolic consequences of immune checkpoint inhibitors: A new challenge in clinical...
• Article: The role of metabolic diseases in cardiotoxicity associated with cancer therapy:...
• Drug Reactions -- see more articles

Reference Desk

• MedlinePlus: Drug Information - Information on prescription and over-the-counter medicines and supplements Also in Spanish

Find an Expert

• Food and Drug Administration

Children

• Drug Eruption (Pediatric) (Logical Images)

Older Adults

• Medications Older Adults Should Avoid or Use With Caution (AGS Foundation for Health in Aging)

Patient Handouts

• Angioedema (Medical Encyclopedia) Also in Spanish
• Drug allergies (Medical Encyclopedia) Also in Spanish
• Drug-induced diarrhea (Medical Encyclopedia) Also in Spanish
• Drug-induced tremor (Medical Encyclopedia) Also in Spanish
• Taking multiple medicines safely (Medical Encyclopedia) Also in Spanish