Cold sores are painful lumps or blisters on the face. They're caused by a virus and are very contagious.
A cold sore usually starts with a tingling, itching or burning feeling. Over the next day or 2, a painful lump or blister will appear on your face.
Treatments for cold sores include antiviral creams and cold sore patches you can get from a pharmacy.
Read more on the NHS website.
A cold sore usually starts with a tingling, itching or burning feeling. Over the next day or 2, a painful lump or blister will appear on your face.
Check if it's a cold sore
A cold sore usually starts with a tingling, itching or burning feeling.
Over the next 48 hours:

Small fluid-filled blisters appear.

The blisters can appear anywhere on the face.

The blisters burst and crust over into a scab.
Cold sores should start to heal within 10 days, but are contagious and may be irritating or painful while they heal.
Some people find that certain things trigger a cold sore, such as another illness, sunshine or menstrual periods.
Read more on the NHS website.
Treatments for cold sores include antiviral creams and cold sore patches you can get from a pharmacy.
Self-care
Cold sores take time to heal and they're very contagious, especially when the blisters burst.
Important
Kissing a baby if you have a cold sore can lead to neonatal herpes, which is very dangerous to newborn babies.
Do
eat cool, soft foods
wash your hands with soap and water before and after applying cream
avoid anything that triggers your cold sores
use sunblock lip balm (SPF 15 or above) if you're outside in the sun
take paracetamol or ibuprofen to ease pain and swelling (liquid paracetamol is available for children) – do not give aspirin to children under 16
drink plenty of fluids to avoid dehydration
Don't
do not kiss anyone while you have a cold sore
do not share anything that comes into contact with a cold sore (such as cold sore creams, towels, cutlery or lipstick)
do not have oral sex until your cold sore completely heals as you could give your partner genital herpes
do not touch your cold sore (apart from applying cream) – if you do wash your hands
do not rub cream into the cold sore – dab it on instead
do not eat acidic or salty food if it makes your cold sore feel worse
Medical treatments
A GP may prescribe antiviral tablets if your cold sores are very large, painful or keep coming back.
Newborn babies, pregnant women and people with a weakened immune system may be referred to hospital for advice or treatment.
Read more on the NHS website.