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What is a cold sore?

Andrew Bellingham

Andrew Bellingham

Pharmacist | 20+ Years | BPharm | Dip Clin Pharm

A cold sore is a common viral infection that causes small fluid-filled blisters around the mouth, lips, or nose.

The visible nature of cold sores may make you feel self-conscious or embarrassed, but with roughly 70% of the UK population having cold sores – there’s really nothing to worry about. 

If you think you have cold sores, don’t wait to see your doctor. Book an online consultation with a pharmacist to get the care and treatment you need.

What are the symptoms of a cold sore?

Cold sores can cause a range of uncomfortable symptoms. They include:

  • Tingling or itching sensation before the appearance of the cold sore

  • Small fluid-filled blisters that can be painful and tender to the touch

  • Red and swollen skin around the blister

  • Blisters may develop into shallow ulcers, which can hurt during eating or speaking

  • When they start to heal, the blisters scab over – with the scabs falling off when the skin underneath has healed

What causes a cold sore?

Cold sores are caused by the herpes simplex virus (HSV), specifically HSV-1. It’s very highly contagious and can be transmitted through close personal contact, especially when the virus is active and causing symptoms. 

Sometimes, it’s possible to transmit the virus when there are no visible symptoms, as the virus may be dormant in the skin cells around the mouth.

Direct contact

The most common way cold sores are spread is through direct contact, usually through kissing and less commonly from oral sex.

Indirect contact

Cold sores can also be transmitted indirectly by sharing things like cups, lipsticks or food with a person with cold sores.

Frequently asked questions about cold sores

What triggers cold sores?

Common triggers for cold sores include stress, fatigue, fever, sun exposure, and hormonal changes. Avoiding these triggers can help prevent outbreaks.

Are cold sores always herpes?

Cold sores are typically caused by the herpes simplex virus (HSV-1). However, not all oral herpes infections result in cold sores.

How long are cold sores contagious?

Cold sores are contagious until they crust over completely, usually around 7-10 days after they first appear.

A woman is about to apply cream to her cold sore, which is just above her upper lip to the right.

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