Demodex folliculorum and Demodex brevis
- Parasite
- For completeness
Microscopic mites that live in almost everyone's hair follicles and oil glands. In large numbers they inflame the eyelids and face.
Also called: follicle mites, eyelash mites
Quick facts
- Type
- Parasite · Ectoparasites
- Gram / shape
- Worm-like
- Spread
- Close contact · Shared towels
- Causes
- Demodex blepharitis · Rosacea · Demodicosis
- Treatment
- Eyelids
At a glance
- Shape
- Worm-like, elongated body with 4 pairs of stubby legs at the front
- Family
- Demodicidae
- Type
- Mites (arachnids), permanent commensal ectoparasites of human follicles
- Size
- D. folliculorum about 0.3–0.4 mm; D. brevis about half that
Morphology
- Elongated, transversely striated body, with the legs and mouthparts at the front end.
- D. folliculorum lives in groups in hair follicles, including eyelashes.
- D. brevis lives alone deeper, in sebaceous and meibomian glands.
Transmission
- Close contact: acquired from parents soon after birth; few in children, more with age.
- Shared towels, pillows and cosmetics may play a part.
- Almost all adults carry them; disease depends on mite numbers and the host's response.
Reservoir: Humans only (each mammal has its own Demodex species)
Isolation precautions
What the care team adds to standard precautions.
- Standard
Life cycle
- Adults mate at the follicle opening, mostly at night.
- The female lays eggs inside the follicle or gland.
- A six-legged larva hatches and becomes a protonymph, then a deutonymph.
- Nymphs move to new follicles and moult into eight-legged adults.
- The whole cycle takes about two to three weeks and happens on the human host.
Virulence factors
- Mites block follicles and glands and damage the lining by feeding on cells and sebum.
- Dead mites and their bacteria trigger inflammation and immune reactions.
- Overgrowth in older adults, people with immunosuppression (such as HIV) and with topical corticosteroid use.
- In the eyelids, mites at the lash base cause collarettes, lash loss and meibomian gland dysfunction.
Diseases it causes
- Demodex blepharitis Blepharitis →
- Rosacea: higher mite numbers, especially in papulopustular forms Rosacea →
- Demodicosis: follicular scaling (pityriasis folliculorum), papules and pustules on the face
- Perioral-like dermatitis and conjunctival inflammation
Clinical picture
- Itchy, red eyelid margins with cylindrical waxy dandruff (collarettes) around the lash base.
- Lash loss, gritty or burning eyes and dry eye symptoms.
- Face: fine follicular scaling, redness, papules and pustules, often asymmetric.
Diagnosis
- Slit-lamp view of collarettes at the lash base strongly suggests ocular Demodex.
- Light microscopy of plucked eyelashes shows mites.
- Skin: standardised skin surface biopsy or scraping; more than 5 mites per square centimetre supports demodicosis.
- Dermoscopy may show spiky white structures plugging follicle openings.
Treatment
Eyelids: daily lid hygiene, warm compresses, tea tree oil preparations or a topical acaricide approved for Demodex blepharitis. Skin: topical acaricides such as ivermectin cream, metronidazole, permethrin or benzyl benzoate; oral ivermectin in severe or immunosuppressed patients.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Regular lid and facial cleansing with non-oily products.
- Avoid heavy oil-based creams and unnecessary topical corticosteroids on the face.
- Do not share towels, pillowcases or eye cosmetics; replace old eye make-up.
Test yourself
Think of the answer, then tap the question to see it.
What eyelid sign is typical of Demodex blepharitis?
Collarettes: cylindrical waxy dandruff wrapped around the base of the eyelashes.
Where does Demodex brevis live?
Alone, deeper in sebaceous glands and in the meibomian glands of the eyelids.
Which skin disease is associated with higher Demodex density?
Rosacea, especially the papulopustular form.
How is demodicosis of the skin confirmed?
By standardised skin surface biopsy or scraping showing more than about 5 mites per square centimetre.
Connections
← Back to the group: Ectoparasites
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Demodex, demodicosis (DermNet, 2023); Blepharitis: MedlinePlus Medical Encyclopedia (MedlinePlus (NLM), 2024); Arthropod infestations. Arachnid bites and stings (DermNet, 2023).
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Representative model, for educational purposes only.