COMMUNITY PHARMACY LECTURE NO.19 PAEDIATRICS I- HEAD LICE HEAD LICE COMMUNITY PHARMACY LECTURE NO.19

BACKGROUND Humans act as hosts to three species of louse; 1- Pediculus capitis (head lice). 2- Pediculus corporis (body lice). 3- Pediculus pubis (pubic lice).

PREVALENCE AND EPIDEMIOLOGY Head lice affect all ages, although they are much more prevalent in children aged 4 to 11 years, especially girls. Studies conducted in schools show wide variation of current lice infestation ranging from 4 to 22% of pupils. Head lice can occur at any time and do not show any seasonal variation.

AETIOLOGY Transmitted by head-to-head contact. Fleeting contact will be insufficient for lice to be transferred between heads. Once transmitted lice begin to reproduce. The adult louse lives for approximately 1 month. The female louse lays several eggs at the base of a hair shaft each night.

AETIOLOGY (continued) Eggs hatch after 7 to 10 days, leaving the egg case attached to the hair shaft (known as a 'nit'). In the course of maturing to adulthood the young louse (the nymph) undergoes three moults. Shortly after maturing, the female louse is sexually mature and able to mate.

ARRIVING AT A DIFFERENTIAL DIAGNOSIS Most parents will diagnose head lice themselves or be concerned that their child has head lice because of a recent local outbreak at school. It is the role of the pharmacist to confirm a self- diagnosis and stop inappropriate sales of products. It should also be remembered that an itching scalp in children is not always due to head lice and other causes should be eliminated.

CLINICAL FEATURES OF HEAD LICE Unless live lice have been found, most patients will present with scalp itching. Itching is caused due to an allergic response of the scalp to the saliva of the lice and can take weeks to develop. However, only a third of patients experience itching. Head lice are most commonly found in the occipital and auricular areas.

CONDITIONS TO ELIMINATE Dandruff Seborrhoeic dermatitis

1- Dandruff Can cause irritation and itching of the scalp. The scalp should be dry and flaky. Skin debris might also be present on clothing.

2- Seborrhoeic dermatitis Affect areas other than the scalp, most notably the face. If only scalp involvement is present then the child might complain of severe and persistent dandruff. In infants the child will have large yellow scales and crusts of the scalp (cradle cap).

PRACTICAL PRESCRIBING AND PRODUCT SELECTION Treatment options include insecticides, wet combing and physical agents. All products have to be used more than once; insecticides have to be repeated 7 days after first application. Wet combing every 4 days for at least 2 weeks. Coating agents, dimeticone and isopropyl myristate also have to be repeated after 7 days.

PRACTICAL PRESCRIBING AND PRODUCT SELECTION (continued) All products, except isopropyl myristate, can be used on children older than 6 months. Dimeticone or wet combing is recommended for pregnant and breastfeeding women.

PRACTICAL PRESCRIBING AND PRODUCT SELECTION (continued) Permethrin Malathion Dimeticone 4% Lotion Isopropyl myristate in cyclomethicone

1- Permethrin Before application the hair should be washed with a mild shampoo and towelled dry. Enough Permethrin should be applied to the hair to ensure the hair and scalp is thoroughly saturated. It should be left on the hair for 10 min before rinsing the hair thoroughly with water.

2- Malathion Available as a liquid, lotion or shampoo. lotions and shampoos are now no longer available. should be applied to dry hair and left for 12 hours before washing off.

3- Dimeticone 4% Lotion Applied to dry hair and the scalp ensuring that the scalp is fully covered. The lotion should be spread evenly from the hair root to the tips. It has to be left on for a minimum of 8 hours (over night is preferable) before being washed out with shampoo.

4- Isopropyl Myristate In Cyclomethicone This is applied in the same manner as dimeticone but the contact time is only 10 minutes. It is only recommended for adults and children over the age of 2 years.