What is usual cause of blepharitis? virus?

Bad luck: It's like eczema or dandruff- some get it, some don't. One needs to keep the lids clean and use antibiotic drops like Azasite or eryhtromycin. Sometimes omega 3/flaxseed supplements help. Its a real nuisance, this blepharitis. See an ophthalmologist.

Face oil: Normal bacteria that live on your skin such as staph aureous sometimes overgrow because there is an abundance of food. The food is the oil secreted by your skin. The lid margins have oil glands too. Your years need oil to prevent easy evaporation of your tears. Treatment of this condition is lid hygiene with baby shampoo.Sometimes topical antibiotic ointment for gram positive bacteria, bacitracin.