According to the American Academy of Pediatrics guidelines, the gold standard for diagnosing an active head lice infestation is the identification of a live nymph or adult louse.
These guidelines recommend an examination of wet hair lubricated with such products as a standard hair conditioner. 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. If no live louse is found, he or she will likely repeat the entire exam at a second appointment.
Your doctor will also look for nits in your child's hair. To find nits, he or she may use a specialized light called a Wood's light, which causes nits to appear bluish. But the identification of nits does not necessarily confirm the diagnosis of an active infestation.
A live nit needs to be near the scalp to incubate. Nits found more than about 1/4 inch (6 millimeters) from the scalp are likely dead or empty. Suspect nits can be examined under a microscope to determine if they're living — evidence of a likely active infestation.
If no live nits are found, they're probably left from a previous infestation and not evidence of an active infestation.
May 18, 2017
- Head lice: Frequently asked questions. Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/lice/head/gen_info/faqs.html. Accessed Jan. 16, 2017.
- Kimberlin DW, et al., eds. Pediculosis capitis. In: Red Book: 2015 Report of the Committee on Infectious Diseases. 30th ed. Elk Grove Village, Ill.: American Academy of Pediatrics; 2015. http://aapredbook.aappublications.org. Accessed Jan. 16, 2017.
- AAP updates treatment for head lice. American Academy of Pediatrics. https://www.aap.org/en-us/about-the-aap/aap-press-room/pages/AAP-Updates-Treatments-for-Head-Lice.aspx. Accessed Jan. 16, 2017.
- Devore CD, et al. Head lice. Pediatrics. 2015;135:1355.
- Head lice treatment. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/lice/head/gen_info/faqs_treat.html. Accessed Jan. 16, 2017.
- Gorkiewicz-Petkow A, et al., eds. Scabicides and pediculicides. In: European Handbook of Dermatological Treatments. Warsaw, Poland: Springer-Verlag Berlin Heidelberg; 2015.
- Yetman RJ. The child with pediculosis capitis. Journal of Pediatric Health Care. 2015;29:118.
- Goldstein AO, et al. Pediculosis capitis. http://www.uptodate.com/home. Accessed Jan. 16, 2017.
- Head lice: Diagnosis. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/lice/head/diagnosis.html. Accessed Jan. 16, 2017.
- Anise. Natural Medicine Comprehensive Database. http://www.naturaldatabase.com. Accessed Jan. 16, 2017.
- Ylang ylang oil. Natural Medicine Comprehensive Database. http://www.naturaldatabase.com. Accessed Jan. 16, 2017.
- Parasites: Lice: Head lice. Centers for Disease Control and Prevention. https://www.cdc.gov/parasites/lice/head/prevent.html. Accessed Jan. 16, 2017.