According to the NHS, the most common causes of the condition are either bacteria or skin conditions such as atopic dermatitis (eczema).
However, blocked oil glands, hormone imbalances, mites and allergies could also be the cause of the problem.
The Cleveland Clinic states there are two different types of the condition – anterior blepharitis and posterior blepharitis.
Anterior blepharitis occurs where eyelashes emerge on top of the eyelid, causing the distinctive red and swollen symptoms.