Pruritus of the eyelids is the main symptom in phthiriasis palpebrarum. It is due to a cutaneous hypersensitivity towards the louse saliva. A gritty sensation, burning sensation, and pain are less commonly observed. This condition may be misdiagnosed since phthiriasis palpebrarum is rarely encountered by physicians and because of the small size and the translucent characteristic of the parasite and its nits, which makes them barely visible. Ocular symptoms may evolve for months before the diagnosis of phthiriasis palpebrarum is established. An associated localized or generalized itching of hair-bearing areas of the body is suggestive of associated phthiriasis pubis.

Attentive examination with slit lamp shows translucent nits which appear as oval structures located at the emergence of the eyelashes. Lice appear as moving and semi-transparent structures. The number of lice is variable (one louse to dozens). Dermatoscopy may lead to similar findings.

Palpebral erythema and/or edema, blepharo conjunctival hyperemia, hematic crusts, and petechial macules of the eyelid skin (secondary to blood feeding by the parasite) are frequently observed. Fecal material is seen as small brownish granules.

Phthiriasis palpebrarum affects generally both eyes, and unilateral eye involvement is less common. Upper eyelids seem the most frequently involved. Visual acuity usually is not altered.

Pre-auricular lymphadenopathy may be noted, especially in case of secondary bacterial infection of eyelid excoriations or parasite bites.

Differential diagnosis of phthiriasis palpebrarum includes anterior blepharitis etiologies, such as seborrheic blepharitis (with sebum deposits on the eyelashes mimicking phthiriasis), eyelid eczema (including atopic dermatitis), staphylococcal blepharitis, rosacea blepharitis, and demodicosis. Eyelid infestation with tick larva may also have a similar clinical aspect as phthiriasis palpebrarum.

Microscopic examination of material withdrawn from the eyelids may confirm the parasitic infestation, revealing lice and nits, and help make the diagnosis of phthiriasis by showing the typical morphology of Pthirus pubis.

Cutting the eyelashes is a radical technique. Physical removal of lice and nits from the eyelashes using forceps may be difficult in non-cooperative patients such as children. The use of botulinum toxin A, at the concentration of 2.5 units per 0.1 ml applied with a swab stick on the eyelashes, may be a cost-effective adjunctive treatment which facilitates physical removal since it induces paralysis of the lice preventing them from adhering to the eyelashes.

Several topical treatments may be used in phthiriasis palpebrarum. Yellow mercuric oxide ophthalmic ointment (older publications), parasympathomimetic agents (physostigmine, pilocarpine), 20% fluorescein, and liquid petrolatum ointment have been reported to be efficient on lice and nits. Topical antiparasitic agents such as natural pyrethrins, pyrethroids, malathion, and lindane (sometimes erroneously reported as gamma-benzene hexachloride) may also be prescribed. 

Parasite destruction may be an alternative to physical removal or topical treatment. Cryotherapy with liquid nitrogen performed under the slit lamp was reported to be efficient by some authors. Some authors have proposed argon laser therapy as an effective treatment for phthiriasis palpebrarum. One session using a 200-micron beam, with duration of 0.1 seconds, and a power of 0.2 W allowed the destruction of both lice and nits. However, this device necessitates a strict eye protection and may not be available on a large scale.

Oral ivermectin may be used as a single dose treatment; however, a second dose may be necessary after seven to 10 days to control newly hatched nits. Oral ivermectin is contraindicated in children younger than five years old and/or weighing less than 15 kilograms, as well as in pregnant and lactating women. 

Treatment of associated body hair infestation, using antiparasitic topical and/or shaving is mandatory.

Clothing, bedding including pillowcases, and towels should be washed at 50 C for half an hour and then heat dried for up to 10 minutes to eliminate both lice and nits. All sexual contacts and family members of a person having phthiriasis palpebrarum should be evaluated for the presence of phthiriasis pubis and phthiriasis palpebrarum, and if necessary, they have to be treated. The effect of such measures in preventing recontamination has been proven.

• Adult blepharitis

• Chalazion

• Dry eye disease 

• Hordeolum

Since sexual activity may cause phthiriasis palpebrarum, patients should be screened for other sexually transmitted infections. If Phthiriasis palpebrarum is diagnosed in a child, the physician should rule out sexual abuse, although manual contamination from infested body hair of the child’s father or mother is the most likely way of transmission. Physical examination and treatment of infested sexual partners are recommended.

When a patient is diagnosed with phthiriasis palpebarum, a referral to an ophthalmologist is recommended. There are several ways to treat the condition and it depends on the extent of infestation and age of the patient. The eye lashes can be cut or one may physically remove the lice and nits. Botox has been used to paralyze the tick, which facilitates removal

Several topical treatments may be used in phthiriasis palpebrarum. Yellow mercuric oxide ophthalmic ointment (older publications), parasympathomimetic agents (physostigmine, pilocarpine), 20% fluorescein, and liquid petrolatum ointment have been reported to be efficient on lice and nits. Topical antiparasitic agents such as natural pyrethrins, pyrethroids, malathion, and lindane (sometimes erroneously reported as gamma-benzene hexachloride) may also be prescribed. 

Parasite destruction may be an alternative to physical removal or topical treatment. Cryotherapy with liquid nitrogen performed under the slit lamp was reported to be efficient by some authors. Some authors have proposed argon laser therapy as an effective treatment for phthiriasis palpebrarum. 

Oral ivermectin may be used as a single dose treatment; however, a second dose may be necessary after seven to 10 days to control newly hatched nits. Oral ivermectin is contraindicated in children younger than five years old and/or weighing less than 15 kilograms, as well as in pregnant and lactating women. 

Treatment of associated body hair infestation, using antiparasitic topical and/or shaving is mandatory.

Since sexual activity may cause phthiriasis palpebrarum, patients should be screened for other sexually transmitted infections. If Phthiriasis palpebrarum is diagnosed in a child, the physician should rule out sexual abuse, although manual contamination from infested body hair of the child’s father or mother is the most likely way of transmission. Physical examination and treatment of infested sexual partners are recommended.