Blood vessel abnormalities
Some experts believe abnormalities in the blood vessels of the face may be a major contributing factor for rosacea. This may explain symptoms of flushing, persistent redness and visible blood vessels.
It's not known what causes these abnormalities. But sun damage may be responsible for degeneration of the elastic tissue of the skin and the dilation of blood vessels.
Recent research has shown external triggers such as ultraviolet (UV) light, spicy food, alcohol (particularly red wine), exercise, stress, heat and cold can lead to the activation of certain molecules within the skin called peptides.
Increased levels of these peptides may in turn affect the immune system or nerves and blood vessels (neurovascular system) of the skin. Activation of these systems can cause dilation of blood vessels, redness and inflammation.
Microscopic mites called demodex folliculorum usually live harmlessly on human skin, but people with rosacea have particularly large numbers, which may play a role in the condition.
It is currently uncertain whether the mite is a cause or an effect of rosacea, although some researchers have suggested the symptoms may be caused by the skin reacting to bacteria in the mites' faeces.
Helicobacter pylori bacteria
Helicobacter pylori bacteria are bacteria found in the digestive system. It's been suggested these bacteria may be a possible cause of rosacea, although a link hasn't been proven.
One theory is the bacteria may stimulate the production of a protein called bradykinin, which is known to cause blood vessels to expand.
Rosacea seems to be more common in families, although it's not clear which genes – if any – are involved or how they're passed on.
Triggers of rosacea
Although they're not thought to be direct causes of the condition, many people with rosacea find certain triggers make their symptoms worse.
Different people can have different triggers, but triggers that have been commonly reported include:
- exposure to sunlight
- hot or cold weather
- strong winds
- strenuous exercise
- hot baths
- spicy foods
- hot drinks
- caffeine – found in tea, coffee and cola
- the menopause
- dairy products
- other medical conditions
- certain medicines – such as amiodarone, corticosteroids and high doses of vitamins B6 and B12