Seeking medical advice is very important to prevent further complications but you should know when you should and when you shouldn't seek help.
These criteria might help you:
1- When there is no improvement of your condition with conservative use of warm compresses and lid hygiene.
2- Worsening of the condition. Sometimes sebaceous carcinoma can be presented with symptoms of blepharitis. Your doctor will be able to differentiate between both.
3- Eye pain.
4- Eye discharge.
5- Red eye.
6- Change in vision either suddenly or gradually. Sudden loss of vision needs immediate medical care. Dramatic change of vision is rarely due to Blepharitis.
7- A sore that appears on the eyelid which is either persist or increase in size. It should be evaluated by your doctor to determine its nature.