ABC Medical Center > Diseases > Head Lice

What is head lice?

11 December 2025

This is a condition where tiny insects lodge in the scalp and feed on its blood, easily spreading through direct and close contact with other people.

Head lice are the size of a sesame seed, meaning between two and three millimeters long. They are usually light gray, although the coloring may vary. They can also be found in the eyebrows and eyelashes, with children being the most vulnerable, especially those of school age or who attend recreational activities.

Their life cycle is approximately 28 days and develops in three phases:

  • Egg or nit.
  • Nymph.
  • Adult louse.

Although direct contact is the most common way of contagion, there are a number of factors that can contribute to the dispersion and contagion of head lice, such as:

  • Hair accessories.
  • Pillows.
  • Headphones.
  • Scarves.
  • Brushes and combs.
  • Hats.
  • Towels.

Head lice can be present on a person’s head for 28 to 30 days, as their eggs live for more than two weeks.

It should be clarified that the presence of lice is not a result of a lack of personal hygiene or social status. Nor are they responsible for the transmission of bacterial or viral diseases.

Signs and symptoms Head Lice

  • Intense itching on the scalp, neck, and ears.
  • Formation of small red bumps or protuberances that can become infected with bacteria.
  • White eggs or nits near the root of each hair that are difficult to remove.

Diagnosis and treatment Head Lice

The doctor will analyze your symptoms and clinical history, and perform an examination of the scalp with a specialized light called a Wood’s light to try to find live lice or nits.

The treatment for head lice involves the use of medication, such as:

  • Use of special medicated lotions, shampoos, and rinses.
  • Dishwashing detergents to dissolve the glue that keeps the nits adhered to the hair shaft.
  • Use of fine-toothed metal combs.
  • Washing clothes and sheets with hot water and detergent.

At the Internal Medicine Department of Centro Médico ABC, we provide medical care services with the highest quality and safety, from the prevention, diagnosis, timely treatment, and follow-up of infectious, respiratory, endocrinological, dermatological, rheumatic, nephrological, gastrointestinal, and hematological pathologies, both chronic-degenerative conditions and acute conditions, through an integral and multidisciplinary model.

Related centers and departments Head Lice

Internal medicine
Radiology and Molecular Imaging
Clinical Laboratory

Fuentes:

  • cun.es
  • kidshealth.org
  • healthychildren.org
  • mayoclinic.org
  • msdmanuals.com
  • medlineplus.gov
  • medigraphic.com

How can we help you?

    The dissemination of the content of this material is for informational purposes only and does not replace, under any circumstance or condition, a consultation with a specialist doctor, for which the ABC Medical Center is not responsible for the different use that may be given to it. If you require more information related to the subject, we suggest you contact the specialist doctor you trust directly.