When you take medicine, your body may react in different ways. Sometimes you may have a side effect. Other times, you may have an allergic reaction.
These are not the same thing. Knowing the difference can help you know when to call your doctor, pharmacist, or get emergency help.
Sometimes it can be hard to tell the difference — the symptoms can overlap. That is why describing exactly what happened is so helpful to your healthcare team.
What Is a Side Effect?
A side effect is an unwanted effect that can happen when you take a medicine. Side effects do not always mean you are allergic to the medicine.
Common side effects may include:
Upset stomach
Headache
Feeling sleepy
Dizziness
Dry mouth
Diarrhea or constipation
Some side effects are mild and may get better as your body gets used to the medicine. Others may need to be checked by your doctor or pharmacist. Serious side effects are also possible, so tell your healthcare team about anything that worries you.
Do not stop taking a prescription medicine on your own. Talk to your healthcare provider or pharmacist first, unless you are having a medical emergency.
What Is an Allergic Reaction?
An allergic reaction happens when your immune system reacts to a medicine as if it were harmful.
Allergic reactions often start soon after a dose — sometimes within minutes to an hour. Some reactions are delayed and may not appear until hours or even days later.
Signs of an allergic reaction may include:
Hives
Itching
A skin rash
Swelling of the face, lips, tongue, or throat
Trouble breathing
Wheezing
Some allergic reactions can become serious very quickly.
When Is It an Emergency?
Call 911 (or your local emergency number) right away if you have signs of a severe allergic reaction, such as:
Trouble breathing or wheezing
Severe swelling of your face, lips, tongue, or throat
Feeling faint, dizzy, or passing out
A fast or pounding heartbeat
Repeated vomiting or belly cramps along with other symptoms
Do not wait to see if it gets better.
Watch for Serious Skin Reactions Too
Not every serious drug reaction looks like hives or wheezing. Call your doctor right away if you have:
A rash that is spreading or blistering
Peeling skin
Sores in your mouth, eyes, or other areas
A rash along with a fever
These can be signs of a serious reaction that needs urgent medical care.
Why Is Knowing the Difference Important?
Your healthcare team needs to know what happened when you took a medicine.
For example, feeling sick to your stomach after taking a medicine may be a side effect. Having hives and trouble breathing may be an allergic reaction.
Knowing what happened can help your doctor and pharmacist make safer choices about your medications.
Your Pharmacist Is Here to Help
Not sure if something you are feeling is a side effect or an allergic reaction? Ask your pharmacist.
At Mountain Care Pharmacy, we want you to feel comfortable asking questions about your medications. Understanding your medicine is an important part of using it safely.
Have questions about your medications? Talk with the Mountain Care Pharmacy team. We’re here to help.
*This information is for education only and does not replace advice from your doctor, pharmacist, or other healthcare provider.
Keep Your Pharmacy Updated
Tell your pharmacy about any medication allergies or reactions you have had.
Try to explain what happened, not just the name of the medicine. Include what symptoms you had and how soon they started after taking the medicine. This information can help your pharmacy better understand your reaction and keep your medication record up to date.
