Cold Sores: Symptoms, Causes & Treatment
Cold sores are a common viral skin condition that causes small, painful blisters, usually around the lips or mouth. They are caused by the herpes simplex virus (HSV-1) and can recur over time.
Cold sores often begin with a tingling or burning sensation before blisters appear. These blisters typically burst, crust over and heal within 1 to 2 weeks.
Although cold sores usually clear up on their own, treatment can help reduce discomfort, speed up healing and lower the risk of spreading the virus to others.
This guide explains the common symptoms, causes and treatments for cold sores, and when it may be helpful to speak to a doctor.
Common Symptoms of Cold Sores
Cold sores tend to develop in stages and may cause noticeable discomfort, particularly during the early phase.
Common symptoms include:
tingling, itching or burning around the lips before a sore appears
small fluid-filled blisters, usually around the mouth
redness and swelling in the affected area
blisters that burst and form a crust or scab
soreness or pain, especially when eating or talking
Some people may also feel generally unwell during an outbreak, particularly the first time, with symptoms such as mild fever or swollen glands.
Cold sores are contagious, especially while blisters are present. If symptoms are severe or frequent, medical advice may be helpful.
What Causes Cold Sores?
Cold sores are caused by the herpes simplex virus (HSV-1). Once a person is infected, the virus remains in the body and can become active again, leading to recurring outbreaks.
Several factors can trigger a cold sore outbreak:
Direct contact
The virus is commonly spread through close contact, such as kissing or sharing items like utensils or lip products.
Weakened immune system
Illness, fatigue or certain medical conditions can make outbreaks more likely.
Stress
Emotional or physical stress may trigger the virus to reactivate.
Sun exposure
Strong sunlight can lead to flare-ups in some people.
Hormonal changes
Changes in hormone levels may increase the likelihood of an outbreak.
Recognising triggers can help reduce how often cold sores occur.
Stages of Cold Sores
Cold sores typically progress through several stages:
Tingling stage
A burning or itching sensation develops before any visible signs.
Blister stage
Small, fluid-filled blisters appear, often in clusters.
Ulcer stage
Blisters burst, leaving shallow open sores.
Crusting stage
The sores dry out and form a scab as healing begins.
Treatment Options for Cold sores
Treatment for cold sores focuses on easing symptoms, speeding up healing and reducing the risk of spreading the virus.
Common treatment options include:
Antiviral creams
Applied early, these may help shorten the duration of an outbreak.
Oral antiviral medication
May be prescribed for more severe or frequent outbreaks.
Pain relief
Over-the-counter pain relief or soothing creams can help reduce discomfort.
Avoiding triggers
Reducing exposure to known triggers, such as excessive sun or stress, may help prevent outbreaks.
Hygiene measures
Avoid touching the sore and wash hands regularly to prevent spreading the virus.
A doctor can advise on the most appropriate treatment, especially if outbreaks are frequent or severe.
When Should You See a Doctor?
You should consider speaking to a doctor if:
cold sores are frequent or severe
sores take longer than 2 weeks to heal
the area becomes very painful or appears infected
you have a weakened immune system
symptoms are affecting your eyes or other areas of the body
Medical advice can help manage outbreaks more effectively and reduce complications.
Concerned about Cold Sores?
You can speak to a doctor to discuss your symptoms and receive medical advice
Book Appointment → Cold Sore Prescription →
How A Doctor Can Help With Skin Conditions:
A doctor can assess skin symptoms and determine the most likely cause. This may involve examining the affected area and discussing your symptoms and medical history.
Treatment may include prescription medication, advice on skincare and lifestyle adjustments, or referral for further investigation if necessary.
Clinical review
This page was reviewed by Dr Ahmad, MB BCH BAO, Medical Director at GP24.
Irish Medical Council Reg. No. 019413
Last reviewed: 30-03-2026.
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