Pubic Pediculosis [pubic lice] (960)


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Phthirus pubis – pubic lice

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The crab louse (phthirus pubis) is transmitted by close body contact. Affects coarse hair of the pubic area, body and rarely the eyebrows and eyelashes.
Incubation period is usually between 5 days and several weeks.

Signs and Symptoms

• Itch (worse at night).
• Red Papules.
• Visible eggs or crab louse (tan/grey in colour) or faecal specks (black).
• Occasionally some individuals can have prolonged, asymptomatic infestation.


• Finding the adult lice and/or eggs seen in affected areas - a magnifying glass may help. Eggs adhere to the hair.
• Blue macules (maculae caeruleae) may be visible at feeding sites.
• Examination under light microscopy can confirm the exact morphology.
• NB: May also affect eyelashes and eyebrows.


General advice
• Avoid close body contact until they and their partner(s) have completed treatment.
• Give detailed explanation of the condition, and clear and accurate written information on applying the treatment. All surfaces of the body should be treated, including the scalp, neck, and face (paying particular attention to the eyebrows and other facial hair).
• Offer STI testing.


Malathion 0.5% Aqueous Lotion (Derbac M) - apply over whole body allow to dry naturally and wash off 12 hours later. Give 100ml• Repeat after 7 daysEyelashes: Simple eye ointment BP can be applied to eyelash and eyelash root bd for 8-10 days, this avoids any eye irritation that may occur if using an insecticide

First Line Treatment

• Consider advising shaving particularly hairy areas prior to treatment.
• Lotions should be applied to all body hair, including the beard and moustache and eyebrows but excluding scalp.
• Following treatment if nits are still attached to the hair shaft then these can be removed by a fingernail or a fine tooth comb.
• To kill any lice or nits remaining on clothing, towels, or bedding, machine-wash and machine-dry those items that the infested person used during the 2-3 days before treatment. Use hot water (at least 50oC) and the hot dryer cycle.
• Items that cannot be laundered can be dry-cleaned or stored in a sealed plastic bag for 2 weeks.
• Mattresses should be vacuumed.
• Avoid close body contact, sexual contact and sharing of clothes, bedding and personal hygiene products until they (and their partner[s]) have successfully completed treatment.

Alternative Regimes

• Permethrin 5% cream (Lyclear Dermal cream). Apply over whole body and wash off after at least 12 hours and may need repeated at 7 days. Permethrin is not licensed for those under 18 years of age. Give 30g-60g.

Partner Notification

• Advise treatment of current sexual partners.
• Partner notification of partners from the previous 3 months.

Potential Adverse Effects of Topical Insecticides

• Skin irritation.
• Discolouration of dyed or permed hair with some topical agents.


• Malathione is preferred but both agents are thought to be safe.

Follow up

• Advise client to re-examine 1 week after final treatment.
• Advise client that dead nits may remain adherent to hairs and can be removed with a special comb.
• Treatment failures should be given the alternative from the above list, also ensure that application has been correct. Phenothrin is an alternative but the alcohol base may be irritant to the genital area.


BASHH (2007) United Kingdom Natural Guideline on the management of Phthirus Pubis infestation.

Clinical Effectiveness Group. [Accessed Feb 2022]

BNF online [Accessed Feb 2022] [Accessed Feb 2022]

West Of Scotland Guideline, approved February 2019 [Accessed Feb 2022]

Last reviewed: 28 March 2022

Next review: 31 March 2024

Author(s): Kay McAllister

Version: 2

Author Email(s): [email protected]

Approved By: Sandyford Governance Group

Document Id: 960