Drug Reactions

Also called: Side effects

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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)

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)
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)
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)

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)

Seniors

Medications Older Adults Should Avoid (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