What Are the Basics of Head Lice?

What is head lice?

Head lice are wingless insects spending their entire lives on the human scalp and feeding exclusively on human blood.

Humans are the only known hosts of this specific parasite, while chimpanzees host a closely related species, Pediculus schaeffi.

Unlike body lice, head lice are not the vectors of any known diseases. Except for rare secondary infections that result from scratching at bites, head lice are harmless, and they have been regarded by some as essentially a cosmetic rather than a medical problem.

Head lice infestations might be beneficial in helping to foster a natural immune response against lice which helps humans in defense against the far more dangerous body louse, which is capable of transmission of dangerous diseases.

What are the possible symptoms of head lice?

Common signs and symptoms of head lice may include:

  • Itching. The most common symptom is itching on the scalp, neck and ears. This happens because louse saliva causes an allergic reaction.
  • Lice on scalp. Lice are small, avoid light and move quickly. So it’s difficult to spot them.
  • Lice eggs (nits) on hair shafts. Nits stick to hair shafts. Incubating nits may be difficult to see because they’re very tiny. However, the presence of nits doesn’t necessarily indicate an active infestation.

What are the causes of head lice?

Direct contact is the most common cause of head lice. Lice transmission is most often within a family or among children who have close contact at school or play.

But lice may spread from one person to another by items such as:

  • Hats and scarves
  • Brushes and combs
  • Hair accessories
  • Headphones
  • Pillows
  • Upholstery
  • Towels
  • Shared furnitures

How to diagnose head lice?

To diagnose an active head lice infestation, your doctor will carefully comb your child’s hair with a fine-toothed comb (nit comb) from the scalp to the end of the hair to look for live lice.

If no live louse is found, he or she will likely repeat the entire exam at a second appointment.

Besides, your doctor will also look for nits in your hair. To find nits, he or she may use a specialized light called a Wood’s light, which causes nits to appear bluish.

How to treat head lice?

Generally speaking, your doctor will recommend an over-the-counter (OTC) medication that kills lice and some of the eggs. OTC medications are based on pyrethrin, a chemical compound extracted from the chrysanthemum flower that is toxic to lice.

OTC medications include:

  • Permethrin (Nix).
  • Pyrethrin with additives (Rid, A200 Lice Treatment).

If the correct use of an OTC treatment has failed, your doctor may recommend a prescription medication. These include:

  • Benzyl alcohol (Ulesfia).
  • Malathion (Ovide).
  • Lindane.

Follow directions on the package for how to use these medications correctly.


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* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.