Head lice can be difficult to eradicate, especially in small children. A patient with an apparent treatment failure needs to be carefully evaluated to determine why the failure occurred so that corrective action can be taken.


Class of Problem



failure in diagnosis

misdiagnosis of relapse

Confirm diagnosis.


psychogenic illness

Evaluate for psychiatric issues.

failure in instructions

inappropriate instructions

Give proper instructions.


misunderstanding of instructions

Help patient understand instructions

failure to use

high cost of products

Give free samples or seek financial assistance.



Help the patient understand the need for treatment. Consider treatment under observation.

inappropriate treatment

inappropriate product

Use correct product.


inappropriate preparation

Use correct preparation (shampoo, etc.).

failure in following instructions

failure to retreat

Retreat properly.


failure to remove live eggs

Instruct in use of nit comb.


insufficient dose-time, frequency and/or quantity of product applied

Apply agent correctly.

failure in prevention of  re-exposure

reinfestation from another person.

Find source and treat both source and patient.


reinfestation from source in environment.

Instruct in how to eliminate lice and eggs in the clothing and environment.

drug failure

incomplete ovicidal activity

Use agent with better ovicidal activity.


acquired resistance to insecticide

Test lice for drug resistance.



(1) misdiagnosis of persistent infection: Some parents find the diagnosis of head lice to be traumatic and afterwards become hypervigilant, mistaking dandruff or other innocuous findings as evidence of persistent infection.

(2) reinfestation from another person: Everyone in the environment needs to be treated simultaneously to prevent retransmission.

(3) reinfestation from source in the environment: Caps and bed linen need to be carefully cleaned to remove eggs and lice.

(4) Some people coating the hair with baby oil, provided that the hair is not too long.

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