What should you know about over the counter fever blister medicine?

A fever blister commonly describes a cold sore: a cluster of small, painful blisters, often on or around the lips, that can crust as it heals. Tingling or burning may come before the visible sore. The word fever does not mean every blister is caused by a fever, and a blister near the mouth can have other causes, including irritation or a bacterial skin infection.

Pharmacy treatments may include a protective cream, a pain-relieving product or an antiviral treatment suitable for cold sores. They work best when started at the earliest tingling stage, but product choice depends on the site, age, medical history and other medicines.

Wash your hands after touching the area, avoid picking the crust, and do not share lip balm, cups, towels or cosmetics while it is active. Keep the skin clean and use the product only as directed. Avoid kissing and oral contact until the sore has healed. A pharmacist can advise on pain relief and whether a non-prescription treatment is suitable.

Arrange prompt medical review if sores are spreading, very painful, repeatedly returning, not healing, or accompanied by marked illness. Seek urgent help for a blister near the eye, eye pain or vision change, confusion, severe headache, breathing difficulty, or a rapidly red and swollen area. Babies, people with weakened immunity and people with eczema should seek advice early after possible exposure or new blisters.

Ask whether the sore looks like a cold sore, which treatment is suitable, how to reduce transmission, and whether another infection such as cellulitis or chickenpox needs to be considered.