Blister from cold
A cold sore is a cluster of fluid-filled blisters usually caused by herpes simplex near the lip border.
The short answer
A cold sore is a cluster of fluid-filled blisters usually caused by herpes simplex near the lip border. It often tingles or burns before blistering, then crusts as it heals.
Why can a cold sore return after it has healed?
The virus can remain in nerve tissue and reactivate after illness, sun exposure, stress, or local irritation. Similar-looking lesions can have other causes, especially when they occur inside the mouth.
How can you protect others while a cold sore is active?
Keep the area clean, avoid picking it, wash hands after touching it, and do not share lip products, cups, or towels while it is active. Ask promptly about antiviral treatment when tingling begins.
When does a cold sore need dental or medical assessment?
Seek assessment if the lesion is severe, recurrent, spreading toward the eye, not healing, or affecting eating or drinking. A clinician should assess extensive lesions or sores in someone with reduced immunity.
Could this lesion be a cold sore or something else?
Ask whether the appearance and location fit a cold sore or another lesion. Ask whether a swab, antiviral medicine, or review of triggers is needed.
Frequently asked questions
Are cold sores contagious?
Yes, active lesions can spread through close contact and shared items.
Can a cold sore occur inside the mouth?
A lesion inside the mouth has several possible causes and should be assessed if persistent.
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Who wrote this page
This library is published by Dental Nation, a licensed dental group practising in the United Arab Emirates. Pages are written and overseen by the same clinical team that treats patients in our clinics, and are held to a fixed editorial standard for safety and accuracy.
This page is patient education, not medical advice, and cannot replace an examination. Anything urgent — facial swelling, trauma, uncontrolled bleeding or severe pain — needs a dentist or emergency care now.