Phthiriasis Palpebrarum

Etiology

Pthirus pubis, the causative organism for phthiriasis palpebrarum, is an hominoxius hematophagous arthropod, an obligate parasite of human beings.[9] This insect belongs to the Pthiridae family and the Pthirus genus. Adults measure up to 2 mm long and are smaller than head (Pediculus humanus capitis) and body (Pediculus humanus corporis) lice.[10] Male parasites are smaller than female ones.[10] Pthirus pubis has a crab-like round body with thick 2nd and 3rd sets of legs and large claws, allowing the parasite to cling to hair. This organism infests mainly pubic hair, inducing phthiriasis pubis. However, Pthirus pubis may spread to other hairy areas, including the abdomen, thighs, chest, axillary region, beard, eyebrows, and eyelashes. This organism has a broad, flat, crab-like body with strong claws adapted for grasping onto hair shafts. Unlike other types of lice, such as the head louse (Pediculus humanus capitis), the pubic louse prefers coarser hair, which is why it is often found in the pubic region and, in the case of phthiriasis palpebrarum, the eyelashes.

Pthirus pubis feeds on blood up to 5 times a day by piercing the skin, which leads to the characteristic symptoms of intense itching, redness, and swelling of the eyelids..[11][12] This parasite cannot live longer than 24 to 48 hours away from its human host. A female louse lays an average of 3 nits daily, which hatch 7 to 10 days later.[13] 

Infestation with Pthirus pubis occurs mainly through sexual intercourse or during interactions between an infested parent and their child. Transmission of Pthirus pubis to the eyelashes may be manual from the infested body hair or during sexual contact. Indirect transmission through clothes or towels contaminated with nits is less frequent and denied by some authors. In rare cases, phthiriasis palpebrarum may be misdiagnosed as blepharoconjunctivitis.[14] Huo et al reported the first case of Phthirus pubis and Demodex of the eyelids in a 48-year-old woman.[15] Biler et al reported a case of uniocular phthiriasis palpebrarum infestation in a young child undergoing amblyopia treatment with occlusion therapy.[16]

Epidemiology

Pubic lice are estimated to infest 1% to 2% of the population globally. The exact prevalence of phthiriasis palpebrarum is unknown. Certain studies estimate phthiriasis pubis to have a prevalence ranging from 2% to over 10%. However, this prevalence is probably underestimated because of frequently undeclared cases treated by 1st-line physicians.

In the Indian population cohort, the cases are underreported due to social barriers and stigmas. Phthiriasis palpebrarum is diagnosed chiefly in children. Approximately 30% of cases are grouped under sexually transmitted diseases.[17] The condition has been reported in a 21-day-old newborn.[18][19][20]

Phthiriasis palpebrarum is a relatively rare condition compared to other forms of lice infestation, such as pediculosis capitis (head lice) and pediculosis corporis (body lice). The disease is more common in crowded, low-hygiene environments, and its spread is often linked to close personal contact, especially in sexually active adults.[21] The primary vector, Phthirus pubis, usually infests pubic hair, but it can migrate to other body hair, including the eyelashes and eyebrows, leading to phthiriasis palpebrarum.[22]

Globally, Phthirus pubis infestation is more frequently observed in adults, especially among people who have poor hygiene practices or live in crowded areas. While both men and women are susceptible to phthiriasis palpebrarum, studies suggest that men may be more frequently affected, likely due to higher rates of sexually transmitted infestations in this group. However, in nonsexually transmitted cases, as when children are involved, the prevalence is more evenly distributed between the sexes.[23]

In children, phthiriasis palpebrarum is more often a result of nonsexual transmission via close contact with an infested caregiver or contaminated personal items such as towels or bedding. Children with poor living conditions, particularly in low-resource areas, have a higher risk of developing this condition. In the United States, the prevalence of Phthirus pubis infestations has declined over the years, particularly with the advent of improved public hygiene and awareness campaigns. However, sporadic cases of phthiriasis palpebrarum still occur, especially in areas with limited healthcare access or in populations with increased sexual activity. In developing countries or regions with overcrowded living conditions, the prevalence of pubic lice infestation and, by extension, phthiriasis palpebrarum may be higher due to poor sanitation and limited access to healthcare.

Data on the global prevalence of phthiriasis palpebrarum remains limited. The condition is often underreported or misdiagnosed due to its rarity and similarity to other eyelid disorders like blepharitis. Nonetheless, case reports from regions such as Africa, Asia, and South America indicate that phthiriasis palpebrarum persists in populations with poor access to hygiene and healthcare services. Overall, phthiriasis palpebrarum remains a rare but notable cause of chronic eyelid irritation worldwide, affecting all age groups and both sexes. However, the transmission dynamics may vary depending on sexual behavior, living conditions, and regional healthcare availability.[24]

Pathophysiology

The lifecycle of the pubic louse consists of 3 main stages: egg, nymph, and adult. Female lice lay around 20 to 30 eggs during their lifespan, which are attached to the hair shaft near the skin (see Image. Phthiriasis Palpebrarum with Severe Anterior Blepharitis). These eggs, also known as nits, hatch into nymphs after about 6 to 10 days, and the nymphs reach maturity within 10 to 15 days. The adult lice can live up to a month on the host if untreated. The organism's entire lifecycle from egg to adult may be completed within 3 to 4 weeks, allowing rapid proliferation if left untreated.[25] The adult lice and their nymphs cause continuous irritation, leading to secondary bacterial infections and blepharitis due to constant rubbing of the eyes.

Phthiriasis palpebrarum is caused by an infestation with Phthirus pubis. This crab-shaped louse primarily affects the pubic area but can migrate to other hair-bearing regions, including the eyelashes. Itching is believed to be due to cutaneous hypersensitivity toward the louse's saliva. Adult pubic lice can infect hairs of the scalp, axillary region, trunk, thighs, groin, eyebrows, and eyelashes. Eyelash involvement is rare, but if present, it is primarily due to crab louse and very rarely due to head louse. Eyelash involvement by body louse is not seen. The lice attach to the eyelash bases, where they feed on blood by piercing the skin. Their feeding leads to the release of saliva, triggering an inflammatory response in the host, causing itching, redness, and eyelid swelling.

The pubic louse can quickly move from the genital areas to other hairy areas, including the eyelashes. In contrast, adult lice are transmitted by contact with contaminated hands, clothes, towels, or linen. In children, eyelash infestation raises the possibility of sexual abuse, which should be carefully ruled out.[26]

Typical clinical findings include pruritus, redness of the eyelid margins, and lice and nits visibly attached to the lashes. In more severe or prolonged cases, conjunctivitis, blepharitis, or keratitis may occur as complications. In rare instances, chronic irritation may lead to loss of eyelashes (madarosis) or lid margin scarring. Overall, the pathophysiology is characterized by the parasitic activity of the lice, leading to mechanical irritation and an allergic inflammatory response, which are compounded by scratching and rubbing.[27]

Histopathology

Phthirus pubis, with a broad and flat body, measures about 2 mm on macroscopic examination. The adult louse has 6 legs (3 pairs) abutting the abdomen. The anterior pair of legs are thinner, having narrow claws and a jagged surface. The posterior pair of legs is thicker to better hold the hair shafts and attach the eggs. The eggs are tiny, translucent, 0.5 mm in size, and stuck to the hair shaft, increasing the likelihood of getting misdiagnosed as blepharitis. 

Histopathology of phthiriasis palpebrarum is not commonly performed due to the condition's external nature and the fact that diagnosis is typically made based on clinical presentation. However, certain characteristic features may be observed when histopathological examination is performed. The primary finding is inflammatory infiltration by lymphocytes, macrophages, and eosinophils, resulting from the allergic reaction triggered by the lice's saliva during feeding. This inflammation can cause redness, swelling, and itching in the affected area.[28]

Additionally, mechanical trauma from the lice's attachment to the eyelashes and the patient’s scratching can lead to epidermal disruption and excoriation at the eyelash bases. These injuries may also predispose the area to secondary bacterial infections. Under microscopic examination, lice and nits may be seen attached to the hair shafts, confirming the diagnosis. Prolonged inflammation may cause epidermal hyperplasia, leading to skin thickening, especially around the eyelid margins.

While histopathological analysis is not typically necessary for diagnosing phthiriasis palpebrarum, it can be used as a confirmatory step, showing clear evidence of parasitic presence and the body's inflammatory response to the infestation.[29]

History and Physical

Itching of the eyelids is the main symptom of phthiriasis palpebrarum. Persistent scratching, rubbing of the eyelashes, and pruritis may lead to diffuse inflammation. A gritty sensation, redness, hyperemia, swollen eyelids, reddish-brown crusts, watering, whitish discharge, burning sensation, irritation, and pain are less commonly observed.[30] Phthiriasis palpebrarum may be misdiagnosed since physicians rarely encounter patients with this condition. Additionally, the nits and parasites' small size and translucent appearance make them barely visible. Ocular symptoms may evolve for months before the diagnosis of phthiriasis palpebrarum is established. Localized or generalized itching of hair-bearing areas of the body is suggestive of associated phthiriasis pubis. Lid abscesses have been occasionally reported.[31]

Careful examination with a slit lamp shows translucent nits, which appear as oval structures located at the emergence of the eyelashes. Lice appear as moving and semitransparent structures. The number of lice varies from 1 to dozens. Dermatoscopy may yield similar findings.[32] Palpebral erythema and edema, blepharoconjunctival 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 generally affects both eyes, and unilateral eye involvement is less common. The upper eyelids seem the most frequently involved. Visual acuity is usually unaltered. Preauricular lymphadenopathy may be noted, especially in cases of secondary bacterial infection of eyelid excoriations or parasite bites.[33] 

Phthiriasis palpebrarum is typically associated with a history of periocular pruritus, particularly in the eyelid margins. Patients may also report eye irritation, redness, and tearing. The condition is more common in individuals with poor hygiene, crowded living conditions, or a history of sexual contact. Phthirus pubis, the pubic louse, is the causative organism and may be transmitted through intimate contact. Some patients may have a history of other louse infestations, particularly in the pubic area, as lice can migrate to different body parts, including the eyelashes.

On physical examination, patients often present with red, inflamed eyelids. Careful inspection under magnification via slit-lamp biomicroscopy typically reveals lice clinging to the eyelashes and eyebrows. Adult lice are often found attached at the bases of the lashes, while nits may be firmly attached to individual lash hairs. Excoriations from scratching are common, and secondary infection arising from skin barrier disruption may be evident.[34]

The eyelid margins may appear crusty or scaly, and conjunctival hyperemia may be present due to irritation. Patients with chronic infestation may also exhibit madarosis due to frequent rubbing. Blepharitis and conjunctivitis may develop if the condition is not promptly treated. A thorough history and physical examination are essential to diagnose phthiriasis palpebrarum accurately, as it can easily be misdiagnosed as blepharitis or another eyelid condition.[35]

Evaluation

The diagnosis of phthiriasis palpebrarum is primarily based on clinical grounds, emphasizing the value of a careful physical examination. Additional laboratory and diagnostic tools may be used to confirm the condition or rule out differential diagnoses. Below is a detailed description of the evaluation process based on current guidelines.

Clinical Evaluation

The primary diagnostic method for evaluating phthiriasis palpebrarum involves careful visual inspection of the eyelashes and eyelids, typically using a slit-lamp biomicroscope. The lice and nits may be visible, clinging to the eyelashes, and the adult lice may sometimes be observed moving. Key clinical signs include eyelid itching, conjunctival inflammation, and grayish or reddish-brown deposits at the bases of the lashes.[36]

Laboratory Tests

Laboratory testing may include microscopy, skin scraping, and staining techniques. Microscopy can confirm the diagnosis by examining lice or nits removed from the eyelashes with forceps. Light microscopic examination of wet mounts (10x magnification), wood lamp assessments, or histopathological analysis of material from the eyelids may confirm parasitic infestation by revealing lice and nits. These methods help diagnose phthiriasis by showcasing the typical morphology of Pthirus pubis.[37] The characteristic crab-like appearance of Pthirus pubis can help differentiate it from other types of lice. Skin scraping of affected areas may also be performed in preparation for microscopic identification of the lice or nits. Although not routine, stains like the Giemsa stain may be applied to clinical samples to highlight the lice or eggs.

Dermoscopy

Dermoscopy, also called "dermatoscopy" or "epiluminoscopy," is a method of skin evaluation that uses skin surface microscopy. Dermoscopy is a safe and confirmatory diagnostic method for assessing louse infection without the risk of physical damage.[38]

Polymerase Chain Reaction and DNA sequencing

Polymerase chain reaction and DNA sequencing may be considered during forensic investigations if sexual trauma and abuse are suspected. Polymerase chain reaction can detect host DNA from the blood ingested by the louse.[39]

Radiographic Imaging

Radiographic evaluation is often unnecessary in the diagnosis of phthiriasis palpebrarum. The condition is localized to the eyelid and diagnosed clinically or microscopically.

International and National Guidelines

The Centers for Disease Control (CDC) recommends visual identification of the lice and eggs on the affected individual. For eye involvement, the CDC advises manual removal of the parasite with fine forceps or tweezers and avoidance of harsh chemical substances near the eye.

Additional Considerations

Given that Pthirus pubis is often transmitted through sexual contact, obtaining a thorough sexual history is critical. Coinfection with sexually transmitted infections should be ruled out. A follow-up examination may be required to ensure the infestation has been successfully eradicated, especially since nits can reappear after successful treatment.

Therefore, the diagnosis of phthiriasis palpebrarum is primarily based on clinical inspection, supported by microscopic confirmation. National and international guidelines emphasize the importance of noninvasive treatments around the eye and recommend ensuring lice eradication to prevent recurrence.

Treatment / Management

The management of phthiriasis palpebrarum focuses on eliminating the lice and nits while maintaining eyelid and ocular health. Below is a detailed description of the treatment options, including medical, surgical, and preventive interventions, guided by national and international guidelines.

Manual Removal

The primary mode of treatment involves the manual removal of lice and nits using fine forceps or tweezers under magnification. This method is often preferred due to the delicate nature of the eyelids and the proximity to the eyes, making chemical agents less desirable. The procedure must be repeated every few days since nits can remain attached to the eyelashes after manual removal. A follow-up examination is often recommended to ensure the infestation has been cleared.[40](A1)

Topical Treatments

Applying petrolatum ointment to the affected eyelashes can suffocate lice. The ointment is generally applied 2 to 4 times daily for 10 days. This approach is safe, especially in pediatric patients, and is widely recommended by national and international guidelines. Petrolatum also inhibits the louse’s ability to attach to the eyelash, reducing its reproduction capacity. Continued application helps prevent the hatching of nits.

While effective in treating lice on other parts of the body, insecticidal agents such as permethrin and pyrethrin should be used cautiously around the eyes due to their potential to cause irritation or toxicity. These treatments are generally not the first choice for eyelid infestations and should be avoided unless carefully prescribed by an ophthalmologist.

Oral Medications

Oral ivermectin may be prescribed in cases of extensive infestation or when manual removal is ineffective. Ivermectin effectively kills lice, including Pthirus pubis, and is often used with topical treatments. Depending on the severity of the infestation, 1 or 2 doses may be required. Oral antihistamines, such as diphenhydramine, may be prescribed to reduce the itching and discomfort caused by the infestation.[41]

Topical Drugs

Several topical treatments may be used to control the symptoms and prevent complications from phthiriasis palpebrarum. Yellow 1% mercuric oxide ophthalmic ointment (recommended in older publications), 0.3% tobramycin eye ointment, 0.5% moxifloxacin eye ointment, parasympathomimetic agents like physostigmine ointment and 4% pilocarpine gel, liquid vaseline, topical botulinum toxin, 20% fluorescein, and liquid petrolatum ointment have been reported to be effective. Topical antiparasitic agents such as natural pyrethrin, pyrethroids, 1% permethrin, 0.2% phenothrin, 0.5% to 1% malathion in topical or shampoo form, 50% tea tree oil, and lindane (sometimes erroneously reported as γ-benzene hexachloride) may also be prescribed.

Other Interventions

Topical antibiotic ointments like erythromycin and bacitracin may be applied to prevent disease and promote healing if a secondary bacterial infection has occurred due to scratching or irritation.[42] Surgical interventions are typically not indicated for phthiriasis palpebrarum, as noninvasive methods can effectively manage the condition.(A1)

Washing and disinfecting any clothing, bedding, towels, or personal items that may have come into contact with the infected person is critical due to pubic lice's contagiousness. Bedding should be washed at high temperatures (at least 60°C) to kill the lice and nits. All sexual partners and close contacts should be examined and treated if infested, as phthiriasis palpebrarum is often associated with pubic lice infestations.[43](B2)

National and International Guidelines

The CDC recommends careful manual removal, petrolatum application, and patient education to prevent reinfestation. The CDC also emphasizes the importance of avoiding insecticidal treatments around the eyes. Meanwhile, the World Health Organization stresses the necessity of environmental control and treating sexual partners in cases of body or pubic lice infestations, given that phthiriasis palpebrarum is frequently linked to pubic lice.[44] Treating sexual partners and close contacts and maintaining good hygiene are recommended to prevent reinfestation. 

Mechanical Removal

Cutting the eyelashes is a radical measure. Using forceps and removing lice and nits from the eyelashes may be difficult in uncooperative patients, such as children. The use of botulinum toxin A, at a concentration of 2.5 units per 0.1 ml applied with a swab stick on the eyelashes, may be a cost-effective adjunctive treatment. The toxin facilitates physical removal by inducing paralysis of the lice and preventing them from adhering to the eyelashes.[45]  (B3)

Cryotherapy and Argon Laser Therapy

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.[46] Argon laser therapy has been proposed as an effective treatment for phthiriasis palpebrarum.[47] One session using a 200-μ beam, with a duration of 0.1 seconds and a power of 0.2 W, allowed the destruction of both lice and nits. However, this device necessitates strict eye protection when used and may not be available on a large scale.(B3)

Role of Ivermectin

Oral ivermectin may be given as a single-dose treatment. However, since the drug's half-life is 16 hours, a second dose may be necessary after 7 to 10 days to control newly hatched nits. Oral ivermectin is contraindicated in children younger than 5 and weighing less than 15 kilograms. Ivermectin can cross the blood-brain barrier and result in untoward side effects in pregnant and lactating women. Ivermectin blocks the chemical signals through the synaptic channels of the nerve. The drug disrupts the effects of the neurotransmitters glutamate and γ-aminobutyric acid, paralyzing the parasite and resulting in death.[48]

General Hygienic Measures

Treating the associated body hair infestation with a topical antiparasitic and shaving is mandatory. Clothing, bedding, pillowcases, and towels should be washed at 50 °C for half an hour and then heat-dried for 10 minutes to eliminate lice and nits. All sexual contacts and family members of an affected individual should be evaluated for the presence of phthiriasis pubis and phthiriasis palpebrarum and treated if diagnosed. The effect of such measures in preventing recontamination is a proven strategy.

Thus, phthiriasis palpebrarum is treated effectively with manual removal, topical ointments such as petrolatum, and, occasionally, oral medications. Adhering to national and international guidelines, including the treatment of close contacts and environmental control, is essential for successful treatment and recurrence prevention.

Differential Diagnosis

In cases where phthiriasis palpebrarum is suspected but not confirmed, evaluation for Demodex mites, another common cause of blepharitis, may be conducted. Microscopic examination of eyelash hair follicles is typically performed to differentiate between the 2 conditions.[49] Other alternative diagnoses that must be considered include:

• Seborrheic blepharitis
• Blepharoconjunctivitis
• Bacterial conjunctivitis
• Viral conjunctivitis
• Allergic conjunctivitis
• Follicular conjunctivitis
• Chalazion
• Dry eye disease 
• Hordeolum
• Eyelid eczema
• Rosacea blepharitis
• Staphylococcal blepharitis
• Atopic dermatitis
• Demodicosis
• Marginal keratitis

These conditions may present with eyelid erythema alongside pain or itching. However, identifying phthiriasis palpebrarum lice and nits on the eyelashes differentiates phthiriasis palpebrarum from clinical mimics.

Treatment Planning

Phthiriasis palpebrarum does not require radiation therapy. Instead, the treatment involves carefully planning and implementing topical and mechanical interventions.

Prescriptions and Doses

The primary treatment for phthiriasis palpebrarum involves applying petrolatum (Vaseline) ointment to the eyelashes and eyelid margins 2 to 3 times daily for 7 to 10 days. Petrolatum suffocates the lice and prevents further infestation. Antiparasitic drugs such as 1% permethrin cream and oral ivermectin may be prescribed, depending on the extent of the infestation.

Target and Volume

The treatment targets the eyelashes, eyelid margins, and periocular skin. Special attention is required to remove or kill all lice and nits. Manual removal of nits with fine forceps may be necessary.

Techniques

Manual lice removal using fine forceps under magnification is recommended, especially in severe infestations where topical treatments may be insufficient. Applying petrolatum ointment or other antiparasitic creams to the affected areas suffocates and helps eliminate the lice. Implementing hygienic measures, such as cleaning bedding, washing clothes at high temperatures, and avoiding shared towels or contact with infected individuals, is essential to prevent reinfestation. Treating sexual partners is necessary when the infestation is associated with pubic lice, as reinfestation commonly occurs through close contact.[50]

Follow-Up Care

Follow-up is essential to monitor the patient's treatment response and eradicate the infestation. Repeating the treatment may be necessary if lice or nits persist. Reinfection or incomplete treatment may require another cycle of therapy and continued hygiene practices. Comprehensive planning, careful monitoring of symptoms, and education about hygiene practices are crucial to preventing recurrence and ensuring complete treatment success.

Staging

Phthiriasis palpebrarum does not follow a formal staging system like cancer or other progressive diseases. However, the condition may be classified in terms of severity and extent of infestation, which can inform treatment decisions. A rough framework of progression is as follows:

Mild Infestation (Early Stage)

Mild infestation is characterized by a small number of lice and nits localized to a few eyelashes, associated with mild itching or discomfort around the eyes. No significant secondary symptoms, such as blepharitis or conjunctivitis, are present, making this stage easily treatable with manual removal and topical treatments.

Moderate Infestation (Mid Stage)

Moderate infestation involves a more widespread presence of lice and nits, affecting multiple lashes and eyelid margins. This stage is associated with moderate itching and irritation, along with possible redness or inflammation of the eyelids. Early signs of secondary infection, such as blepharitis, may develop, necessitating more extensive treatment that includes careful manual removal, frequent applications of topical ointments, and, possibly, oral antiparasitics. 

Severe Infestation (Late Stage)

Severe infestation features an extensive infestation of lice and nits across most or all lashes on both eyelids. This stage is marked by severe itching, irritation, and inflammation, often leading to secondary complications, such as conjunctivitis, blepharitis, and localized skin infections. More aggressive treatment approaches may be required, including repeated manual removal, systemic treatment, and ongoing hygiene measures to prevent reinfestation.

This staging system is not formal, but it should help understand the condition's progression and appropriate severity-based treatment strategies.

Prognosis

The prognosis of phthiriasis palpebrarum is excellent, with appropriate and timely treatment. Infestation usually resolves without permanent damage to the eyelids or eyes, provided secondary infections are avoided. Patients should be reexamined after 7 to 10 days to ensure complete eradication of the lice and nits.

The prognosis of phthiriasis palpebrarum is generally favorable, and long-term complications are rare. Irritation and inflammation typically resolve once the lice and nits are successfully eradicated through mechanical removal and antiparasitic therapies. Most patients experience full recovery without lasting damage to the eyelids or eyelashes. Secondary infections, such as blepharitis or conjunctivitis, may be managed effectively with appropriate antibiotic or anti-inflammatory therapy.

The recurrence rate is low, especially when proper hygiene is maintained and preventive measures are implemented. Reinfestation can occur if the patient's close contacts or personal belongings, such as towels or bedding, are not treated or cleaned correctly.

Untreated or delayed cases may lead to more severe secondary complications, such as chronic eyelid inflammation or infection, which may take longer to resolve. Neglected cases with chronic infestation can manifest as blepharitis, meibomian gland dysfunction, and dry eyes, which require targeted treatment.

Complications

The potential complications of phthiriasis palpebrarum include the following:

• Meibomian gland dysfunction: Blockage or inflammation of the oil-producing Meibomian glands leads to dry eye symptoms and irritation (see Image. Phthiriasis Palpebrarum with Meibomian Gland Dysfunction).
• Lid abscess: A localized accumulation of pus in the eyelid may arise from a bacterial infection secondary to scratching or manipulation.
• Dry eyes: A lack of proper tear production due to Meibomian gland dysfunction or inflammation leads to discomfort and a gritty sensation.
• Blepharitis: Inflammation of the eyelids occurs due to irritation from lice.
• Chronic conjunctivitis: This condition is characterized by a secondary bacterial or viral infection of the conjunctiva.
• Keratitis: Inflammation of the cornea results from prolonged irritation.
• Madarosis: Loss of eyelashes may result from chronic irritation and scratching.
• Secondary bacterial infections: Scratching and skin barrier breakdown make the skin vulnerable to bacterial invasion.
• Corneal abrasions: Damage to the corneal surface occurs from excessive rubbing or scratching.
• Superficial punctate keratitis: Multiple tiny areas of epithelial damage on the cornea are present in this condition.
• Chronic eyelid inflammation: Persistent swelling and redness of the eyelids characterize this condition.
• Folliculitis: Infection of the eyelash hair follicles occurs due to persistent inflammation and subsequent bacterial invasion.
• Preseptal cellulitis: The eyelid skin and tissue can also become infected.
• Hypersensitivity reactions: Localized allergic reactions to lice bites or secretions can arise.
• Erythema and edema: Redness and swelling of the eyelids result from prolonged infestation.
• Persistent itching and discomfort: The discomfort can persist for some time, even after the infestation has resolved.
• Eyelid scarring: Scarring can develop on the eyelids in chronic or severe cases.
• Discomfort and emotional distress: Anxiety and psychological distress can arise from dealing with a parasitic infestation.

Prompt diagnosis and treatment of phthiriasis palpebrarum help avoid these potential issues.