What Is Demodex and Seborrheic Blepharitis and How Do They Relate to Anterior Blepharitis?

When patients ask about persistent eyelid irritation, I immediatlely look for signs of BLEPHARITIS. Two common subtypes are Demodex Blepharitis and Seborrheic Blepharitis. In general, both are types of ANTERIOR BLEPHARITIS but each affects the eyelash line differently so the treatment is different. Below, I’ve included clinical photos to help you understand what I look for in the exam room. In this blog post I'll be talking about the clinical signs of each only.

Demodex Blepharitis

Demodex mites live in hair follicles and glands. When they overpopulate, they cause an inflammatory response along the eyelid margin. Under magnification, you’ll see collarettes—small, cylindrical flakes—attached at the base of the lashes. Here are 4 examples of Demodex bleaphritis, all showing collarettes around the eyelashes. Lots of variations, so it does take a good, clinical eye to diagnose the more subtle cases.

Collarettes are a waxy sleeve that is buildup from mite waste and eyelash gland debris. Collarettes are always a 100% diagnosis for Demodex mites. If you have collarettes, you have Demodex mites. 

A special note. Because demodex mites inhabit both the lash follicles and meibomian glands, Demodex can also present as ANTERIOR BLEPHARITIS (surface collarettes and crusting) and also lead to POSTERIOR BLEPHARITIS when the meibomian glands become inflamed. The patient may feel itchiness, experience redness, and notice increased tearing.

Seborrheic Blepharitis

Seborrheic blepharitis is linked to oily skin conditions like dandruff. Greasy scales and flakes accumulate along the lashes, resembling cradle cap on the eyelids. The underlying skin often appears reddened and slightly thickened. See the 4 examples of SEBORRHEIC BLEPHARITIS showing greasy scale-like flakes at the eyelash line. The eyelid debris is consistent with oils and dead skin cells that can cause a lot of irritation to the eyelids very similar to eczema. 

Seborrheic blepharitis typically presents as ANTERIOR BLEPHARITIS, since the flakes and oil sit right on the eyelashes. However, if the oily secretions extend into the meibomian glands, the patient can also develop a POSTERIOR BLEPHARITIS —plugged glands, thickened oil, and tear film instability.

Connecting The Anterior and Posterior Blepharitis Bits Together

Both Demodex and seborrheic forms usually start out as an ANTERIOR BLEPHARITIS and then encompass more of the eyelid and also become POSTERIOR BLEPHARITIS. Here, I call it MIXED BLEPHARITIS - some of both. 

• ANTERIOR BLEPHARITIS Signs: Look for collarettes or greasy flakes at the eyelash base. There may be redness and mild swelling of the eyelid skin. I also look for dandruff on the eyebrows. The older the patient, the more likely it's SEBORRHEIC, but I have seen it in young adults too.

• POSTERIOR BLEPHARITIS Signs: Inspect the meibomian gland orifices along the inner eyelid margin. Gland plugging, thick secretions, and scalloping along eyelid margin point to deep meibomian gland involvement.

For example, Demodex mites often trigger anterior collarettes first but quickly inflame glands, bridging into posterior disease. Seborrheic oil can sit on the surface initially, but when it mixes with bacteria and debris, it clogs gland ducts and leads to posterior complications.

Hi, I’m Dr. Tanya Gill, optometrist and founder of We Love Eyes. I started We Love Eyes in 2014 while trying to help one of my (stubborn) patients with contact lens discomfort. In 2016, I had 3 products. Fast forward to today - We Love Eyes has almost 30 SKUs. It’s been an amazing journey. Explore my life’s work at weloveeyes.com. Check out my BLEPHARITIS COLLECTIONsection to find healthy eye care products for your eye problem. I also have a ton of content atTIKTOK. See the profile page and see the playlist BLEPHARITIS. xo

• ANTERIOR BLEPHARITIS - see the tutorial blog here

• POSTERIOR BLEPHARITIS - see the tutorial blog here

• We Love Eyes BLEPHARITIS guide - SHOP Blepharitis Collection

• BLEPHARITIS

• Demodex Blepharitis

• Seborrheic Blepharitis

• We Love Eyes

• anterior blepharitis vs posterior blepharitis

• eyelid margin debris

• meibomian gland dysfunction

• lid hygiene routine

• warm compress for blepharitis

• mite infestation eyelids

• Dr. Tanya Gill