Mouth ulcers often first start with a little tingling or pain in the skin, and then a couple of small fluid-filled blisters (1-3 mm in size) appear.
These burst and there are sores and cracks, sometimes with crusts.
Duration is 7-10 days.
Fever and feeling sick can occur at the same time.
A white spot may remain on the skin after the infection is over.
The cause is the herpes simplex virus (HSV), which many people are infected with as children or young people.
The virus lies "dormant" in the body, and is activated from time to time.
Some people can get mouth ulcers many times a year, but fortunately, after months or years, outbreaks will almost always become less frequent.
Mouth ulcers can be triggered by infections (hence the name cold sores), sunlight, stress, cold, menstruation and pregnancy .
For many, palliative treatment with a lip balm is sufficient.
You can buy non-prescription creams at the pharmacy, but unfortunately the effect is not always that good.
For those who have frequent mouth ulcers, a doctor can write a prescription for tablets (valaciclovir), and these must be used as soon as the outbreak starts.
Tablets are considered more effective than cream.
Mouth ulcers can be prevented by sun protection.