Signs & symptoms
What HSV-1 looks and feels like
HSV-1 shows up differently from person to person — and in many people, not at all. Here's the full range, from the classic cold sore to the more intense first infection.
The most common sign: cold sores
The hallmark of HSV-1 is the cold sore (also called a fever blister): a small cluster of fluid-filled blisters, usually on or around the lips, that break open, weep, and crust over before healing. An outbreak often starts with a day or so of tingling, itching or burning at the spot before the blister appears. Most cold sores heal on their own within about 1–2 weeks.
The first infection can be more intense
A person's very first HSV-1 infection (the "primary" infection) is often the most noticeable, and can be more severe than later recurrences — especially in young children. It may include:
- Multiple painful sores inside the mouth and on the gums (a condition called herpetic gingivostomatitis)
- Fever, body aches and a general feeling of being unwell
- Sore throat and swollen, tender lymph nodes in the neck
- Difficulty eating or drinking because of mouth pain
After this first episode settles, the virus becomes dormant in the nerves and may reactivate later as milder, shorter outbreaks.
Recurrences and their triggers
When HSV-1 reactivates, outbreaks tend to appear in the same area each time and are usually briefer and less severe than the first. Common triggers include:
Genital HSV-1
HSV-1 does not only affect the mouth. Through oral contact it can also cause genital herpes, with sores in the genital or anal area. The World Health Organization estimates that around 376 million people aged 15–49 have genital HSV-1 infection. Genital HSV-1 often recurs less often than genital HSV-2, but the first episode can still be painful.
Many people have no symptoms
A large share of people with HSV-1 never develop noticeable sores and may not know they carry the virus. This is normal — and it's also why the virus is so widespread, since it can be passed on without anyone realising. Having no symptoms does not mean the virus is gone.
When symptoms are not "just a cold sore"
Certain symptoms point to something more serious than an ordinary outbreak and need prompt medical attention — a painful red eye or blurred vision, or the neurological warning signs of a brain infection. These are covered in detail on the Serious Risks page.
This needs emergency care
A herpes sore in a newborn baby, a painful red eye or sudden vision change, or HSV symptoms with confusion, severe headache, stiff neck or seizures are emergencies. Don't wait — seek urgent medical help.