Conditions
Cold sores: symptoms, treatment and how to avoid spreading them
Cold sores, also called fever blisters, are blisters on or around the lips, almost always caused by herpes simplex virus type 1. They go away on their own in 1 to 2 weeks, but they are contagious. An antiviral works best when started at the first tingle: the doctor assesses you by video and, if appropriate, prescribes.
Is it an emergency? Call 911.
Is this an emergency?
This is not an emergency service. Call 911 or go to the nearest emergency room if you have:
- Blisters near the eyes: in-person care the same day
- A newborn exposed to a cold sore who has blisters or seems unwell
- A blistering rash spreading quickly in someone with eczema
- Cold sores with a weakened immune system from illness or medicines
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At a glance
Cold sores
Common symptoms
- Itching, burning or tingling on the lips before blisters appear
- Small fluid-filled blisters on or around the lips
- Blisters that break open and crust over
- With the first outbreak, sometimes a sore throat, fever and swollen glands
- Other names
- Fever blisters · Oral herpes · Herpes labialis
- Treatment
- Goes away on its own; a prescription antiviral when the medical evaluation calls for it, best at the first symptom
- Possible complication
- Herpes infection of the eye
On this page(8)
What are cold sores?
According to MedlinePlus, cold sores are almost always caused by herpes simplex virus type 1 (HSV-1), and most people in the U.S. have it by age 20. After the first infection, the virus stays dormant in the nerves of the face and can come back.
It spreads through direct contact with a sore or with the person (a kiss, for example) and by sharing utensils, towels or razors. It can spread even when no blisters are visible. It is not the same as shingles or canker sores, which are not contagious.
How we treat cold sores by video
You see Dr. Diana Nieves Castro, a Puerto Rico–licensed general practice physician with several years of emergency-department experience, in English or Spanish. Cold sores are recognized by looking at them: with good light and the camera close, the doctor sees the blisters and asks when they started, how often you get them, and whether you have any condition that weakens your immune system.
If appropriate, the doctor prescribes an antiviral and we send your prescription to your pharmacy. If the sores are on the genitals, see STI testing and treatment or genital herpes. For other skin problems, see skin and acne care.
This is virtual urgent care for non-emergencies. We see adults and children of all ages; you need to be physically in Puerto Rico during the visit, and visitors are welcome.
Your doctor
Dr. Diana Nieves Castro, MD
General practice physician
Several years of emergency-department experience.
Founding Executive Director of The Health Initiative.
Your visit in 3 steps
Request a visit online 24/7 — we confirm your time by email or text.
Request your visit.
Book a visit and choose "Doctor visit". You pay by card when you request it. If you already take an antiviral and only need a refill, choose "Follow-up visit".
See the doctor by video.
We send you a secure video link. It works on your phone, tablet or computer.
Get your plan.
If appropriate, the doctor prescribes and we send your prescription to your pharmacy.
What a cold sore visit costs
A cold sore outbreak is handled in a US$79 doctor visit, the same price for every age, with no membership. A refill of a medicine you already take is a US$49 follow-up visit. You pay by card when you request the visit, and you get a full refund if the visit can’t take place. See all prices.
Cold sore symptoms
According to MedlinePlus, the most common symptoms are:
- Itching, burning or tingling on the lips before blisters appear
- Small fluid-filled blisters on or around the lips
- Blisters that break open and crust over
- With the first outbreak, sometimes a sore throat, fever and swollen glands
Cold sore treatment and triggers
Cold sores go away on their own in 1 to 2 weeks. Prescription antivirals work best when started at the first warning signs, the tingling or burning, before blisters form. According to MedlinePlus, over-the-counter creams help only a little. What does help: ice or a cold cloth, salt-water rinses, and acetaminophen or ibuprofen for pain, as the label directs.
Outbreaks can be triggered by menstruation or hormone changes, fever, stress and the sun. Puerto Rico’s sun is strong all year: use a lip balm with sunscreen.
- Don’t touch or pop the blisters, and wash your hands if you do touch them.
- Don’t kiss or share utensils, glasses, towels or razors while you have blisters.
- Avoid oral sex during an outbreak.
- Don’t kiss newborn babies while you have a cold sore.
When to get in-person care or go to the ER
According to MedlinePlus, see a doctor if symptoms are severe or don’t go away after 2 weeks, or if your immune system is weakened by an illness or medicines.
Get in-person care the same day if you have blisters near your eyes, because herpes in the eye can cause scarring; if a newborn has been in contact with someone with a cold sore and develops blisters or seems unwell, because herpes in newborns can be serious; or if a person with eczema has a blistering rash that spreads quickly. For your safety, call 911 if a baby has a seizure, won’t feed or has trouble breathing.
How we care for you
We evaluate, diagnose and treat; if needed, we give you a lab order for a lab near you.
We see adults and children of all ages. Patients under 21: a parent with patria potestad (parental authority) or a legal guardian is on camera for the whole visit and shows photo ID.
Real-time video visit. We send you a secure video link. It works on your phone, tablet or computer.
If appropriate, the doctor prescribes and we send your prescription to your pharmacy. We do not prescribe controlled substances.
You must be physically in Puerto Rico during the visit (visitors, tourists and cruise passengers are welcome).
In an emergency, call 911.
Frequently asked questions
How long do cold sores last?
Are cold sores contagious?
When does treatment work best?
Can I kiss a baby if I have a cold sore?
About this page
Author: The Health Initiative
Medical care provided by Dr. Diana Nieves Castro, MD (PR license 24027)
Disclosure: Founding Executive Director of The Health Initiative
Published: 2026-10-02 · Updated: 2026-10-02
Sources (3)
- Oral herpes (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Pregnancy and herpes (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Atopic Dermatitis (NIAMS, NIH) (opens in a new tab) (accessed 2026-10-02)