Ibarra J1*, Vander Stichele RH2, Olsen A,Lapeere H2, Wickenden C1 (2018)

Differing definitions and outcomesof “wet combing” in the eradication

of head lice (pediculosis capitis)

Presentation to the 6th International Congress on Phthiraptera (Lice),Brno, Czech Republic 23­29 June, 2018

1 Community Hygiene Concern, UK Registered Charity 11538242 Ghent University, Belgium *Corresponding author: joanna_ibarra@chc.org

Ibarra J, Vander Stichele RH, Olsen A, Lapeere H, Wickenden C. Differing definitions and outcomes of “wetcombing” in the eradication of head lice (pediculosis capitis). 2018. (Presentation to the 6th InternationalCongress on Phthiraptera (Lice), Brno, Czech Republic 23­29 June, 2018)

Differing definitions and outcomes of “wet combing” in the eradicationof head lice (pediculosis capitis)

Abstract: The purpose of fine­tooth “wet combing” is to locate the motile stages of head lice inthe scalp hair and remove them. According to Medical Research Council guidance, “wetcombing” is a complex intervention with multiple components. Various methods are mentionedin the literature. We classify them in their order of development as Bug Busting wet combing(BBWC), conditioned combing (CC), and wet combing with conditioner (WCWC), to examine theircomponents and the reasons for their use.

We conclude that there is no such thing as generic wet combing and authors should explain thedetails of the method they choose and the rationale for using it. The evidence in favour ofidentification of BBWC as the most sensitive and effective method is incomplete. The findings ofaction research should be independently verified in full­scale field trials. These are basic issues inthe eradication of pediculosis capitis.

Definitions of “wet combing”

The purpose of fine­tooth “wet combing” is to locate the motile stages of head lice in thescalp hair and remove them. The rationale for moistening the hair is that wet lice becomemotionless1,2, and moisture facilitates straightening and combing the hair1. Various methodsare mentioned in the literature for individual diagnoses1 and stand­alone treatment3,4, inpolicy guidelines5,6 and community health promotion7,8,9, in prevalence/incidence surveys10

and as a measure of the cure rate of medication11. The characteristics of the comb and theway it is applied govern the accuracy of the method. Thus “wet combing” is acomplex intervention with multiple components as per the Medical Research Councildefinition (http://www.mrc.ac.uk/documents/pdf/complex­interventions­guidance/)12 and itis beholden on authors to give full details of the method used and the reasons why it is used.On the basis of the details available (some of which are sketchy) differing methods can beclassified as Bug Busting wet combing (BBWC) 1, conditioned combing (CC) 13, and wetcombing with conditioner (WCWC) 10. See Table I.

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Fine combs used: Plastic Bug Buster® 1989­1997Plastic Bug Buster® 1998 onwardsMetal pin Licemeister®Plastic KSL® PDCMetal pin Nisska®Metal pin KSL®

a bc

fe

d

abcdef

1993 ­ 1997 CHC Bug Busting wall charts 1993­97, UK (educational resource)

Plastic Bug Buster 1989 – 1997 (grey)(BB 89­97) a

Shampoo hair | Rinse | Conditioner |comb | Rinse | comb BBWC

1

July 1998onwards

Ibarra J. (1998) 1 andall CHC educational resources 1998 onwards, UK(Guide and other resources widely circulated)

Plastic Bug Buster1998 onwards (bright yellow) (BB 98) b

As 1 above BBWC1A

1998Accessed 28 Oct 98

www.jcu.edu.au/school/phtm/PHTM/hlice/hlinfo1.htmSpeare R.13James Cook University, Australia (educational resource)

Metal, long pin(Licemeister cdescribed as “best”)

NO WATER INVOLVEDThick white conditioner on dry hair | combNo mention of rinsing CC

2

2000 De Maeseneer et al. (2000) 10 Ghent, Belgium Plastic Bug Buster1998 onwards b

Thorough wetting of hair | Conditioner |comb | Rinse | comb WCWC

3

2000 Bingham et al. (2000) 14 Isle of Wight, UK Plastic Bug Buster1989 – 1997 a

As 1 BBWC4

2002Accessed8 May 02

www.education.tas.gov.au/equitystandards/head­licelicefaq.htm 17

Tasmanian Government, Australia (educational resource)

Unspecified INSTRUCTION: “DO NOT WET THE HAIR…”Conditioner on dry hair | combNo mention of rinsing CC

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2007 Ibarra et al (2007) 18 Review of projects in UK, Denmark andBelgium; reference to “application of conditioner to dry hair(Counahan et al, 2005)” 19, Australia. Call to conduct acomparison of the sensitivity of all detection methods

Plastic Bug Buster 1998 onwards b

CHC (UK) method (1 + 1A) & Ghent(Belgium) method (3) described BBWC, WCWC, CC

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2007 Lapeere et al. (2007) 20 Ghent, BelgiumFull­scale comparative trial of diagnostic methods, WCWC isfound to be 1.25 times more sensitive than dry combing

Plastic Bug Buster1998 onwards b

Ghent (Belgium) method (3) described WCWC

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2008 Heukelbach et al. (2008) 21 Brazil KSL plastic precisiondetection (or similar) d

NO WATER INVOLVED “diagnostic wetcombing” “application of a commerciallyavailable conditioner without silicone oil”on dry hair | combNo mention of rinsing CC

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2009 Jahnke et al. (2009) 22 Germany“First, the hair was wetted with a commercially availableconditioner that did not need to be washed out.”

NYDA comb = KSL plasticprecision detection (PDC)d Or Nisska, metal, longpin e (incorrectlydescribed as “square cut”)

NO WATER INVOLVED “Leave­in”conditioner on dry hair | combNo mention of rinsing CC

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2015 Kurt et al. (2015) 24 TurkeyIn Fig. 2, label “wet combing with conditioner”, but in thetext Kurt et al. only mention use of a “lubricant” on dry hairand cite Jahnke et al. (2009) 22

In this paper it is suggested that dry and wet combing areequally sensitive, but it is combing dry hair, v conditioner ondry hair, that are compared.

KSL PDC dOr KSL metal long pin f

NO WATER INVOLVEDLubricant on dry hair | combNo mention of rinsing CC

CHC = Community Hygiene Concern, UKhealth and education charity

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NOTE Hill et al. (2005) 3 UK, describe BBWC, but classify the method as WCWC when using BBWC with BB 98 comb b (yellow)to measure the trial outcome

NOTE Roberts et al. (2000) 15 Wales, UK, tested the BB 89 – 97 a (grey) using BBWC, but dry combing with BB 98 comb b (yellow) was usedto measure the trial outcomePlastow et al. (2001) 16 Devon UK, tested the BB 98 b (yellow) using BBWC, and dry combing with BB 98 comb b (yellow) was used tomeasure initial outcome, switching to BBWC with b to measure sustainability

Table I: Classification of differing “wet combing” methods

Date Reference Fine comb used Method of “wet combing”No.

2012 SA Public Health, Adelaide, South Australia ( 2012) 23

(educational resource)Unspecified Conditioner on dry hair | comb

Suggestion that conditioner is thenrinsed from hair, but no water involved indiagnosis CC

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Table II: Tooth spacing measurements to define the purpose of a fine­tooth comb

Yes Too fineRecommendation:

Dedicated single­purpose combs are required.After a head is free of live lice, nit combing may proceed safely.

0.09 – 0.19 mm

Too wide Yes0.20 – 0.30 mm

Too wide Inefficient0.31 – 0.50 mm

Using a nit comb to detect and remove live lice is inadvisable because lice trapped between thefinely­spaced teeth can remain unseen and be combed back onto the head unharmed.

Nit comb Louse combWidth of gapbetween teeth

Comb design features which influence outcome

A. Confusion between louse detection and nit combs

In much of the literature, the authors fail to distinguish between fine­tooth combs suitable forlouse detection and removal and combs capable of removing nits, instead referring to themcollectively as “nit combs”. The main habitat of head lice is amongst the roots of the hair.Therefore the detection comb must be passed through the hair with the tooth points touchingthe scalp as long as possible.

CHC (2002) 25 summarised the standards that the charity set during the development of the1998 Bug Buster combs for comfortable, speedy, and accurate louse detection, using actionresearch techniques:

• A louse comb is best made entirely in good quality plastic (better than metal pins pegged ina handle)

• The tooth shanks should be square­edged, the points deeply bevelled on the leading edge,and flat at the back (better than rounded) ­ the bevel side is held against the scalp,achieving the best angle for trapping lice as the comb is drawn through the hair

• A tooth span of 4 cm is suitable for the contours of a young child’s head; just over 6 cm isthe maximum practical span on an adult head

• The gaps between the teeth must be just narrow enough to trap the smallest lice, but stillallow the easiest passage possible through the hair ­ it follows that a good louse comb isnot going to exert the traction needed for nit removal.

CHC advises that fine­combs should be divided into either louse or nit comb categoriesaccording to the tooth spacing. See Table II.

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CHC found that the optimum tooth gap in a louse detection comb is 0.26 mm. This is narrowenough to pick up newly hatched head lice combined with ease of passage through the hair,which the lower gauges of 0.25 mm down to 0.20 mm may hinder.

Diagram 1: The purchase on the scalp of various tooth point designs

Scalp

Comb tooth pointsIn profile

(enlarged 2.5: 1)Combs actual size

Bug Buster 1989­97discontinued

Bug Buster1998 – onwards

Assy/ Nit Free(microgroved) 2000 onwards

KSL precision detectioncomb (PDC) 2005 onwards

Comb name

Precision engineeredplastic

Precision engineeredplastic

Long cylindrical metal pinsset in a metal handle

Precision engineeredplastic

Material

1 unit 2 unit + 0.2 unit Less than 1 unitPurchase by unit

louse detection andremoval

louse detection andremoval

detection and removal oflice and nits

louse detection Declared purpose

Bug Buster and PDC carry the instruction to hold the slanted side of the points towards the scalp. The reverse side iscompletely flat. The tooth shanks are square­edged including the points in the case of Bug Buster, but assume ashallow “boat­shaped” rounded slant (KSL Consulting, 2006) 26 at the points in the case of PDC. Acrylonitrilebutadiene styrene (ABS) plastic is commonly used because it combines a certain level of flexibility with strength.Metal pins are unyielding and more likely to cause discomfort.

Notes

Bug Buster® 1989­1997Bug Buster® 1998 – onwardsKSL® PDC *Assy®/Nit Free *

*models distributed to participants ICP3,Buenos Aires, October 2006

d

a

a

a

g

g

b

d

d

g

b

b

B. Purchase of tooth points

The purchase of the tooth point on the scalp governs its leverage. See Diagram 1, whichcompares the discontinued BB 89­97 comb with designs in current use.

C. Comparative purchase with reference to louse detection and removal

The Bug Buster 1998 achieves over twice the purchase of the Bug Buster 1989­97, with morethan twice the length of the slanted tooth surface resting against the skin. It achieves 3 timesmore purchase at any one moment compared with the “boat­shaped” PDC as it “rolls” overthe scalp during combing.

The longer purchase of the Bug Buster 1998 steadies the angle at which the comb is drawnthrough the hair, enhancing the louse detection and removal ability as the tooth point slides under lice at the roots of the hair. The Bug Buster 1998 replaced the discontinued Bug Buster 1989­97.

In cylindrical metal pin combs, the point resting on the scalp covers less than a quarter of thesurface covered by the Bug Buster 1989­97, reducing the chances of picking up lice. The bulkyhandle of metal pin combs interferes with insertion into the hair at the best angle.

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Comparative sensitivity of different methods of “wet combing”It is widely acknowledged that both dry or wet fine­tooth combing are more sensitive than visualinspection22,27. Some research and Guidelines11 suggest that dry combing is as effective asconditioned combing with no prior wetting of the hair. However, it has been shown in a full­scaletrial that WCWC, which involves a thorough wetting, is 1.25 times more sensitive than dry combing(DC) (Lapeere et al. 2007) 20. This finding, coupled with the suggestion that dry and conditionedcombing are equally sensitive (Kurt et al. 2015)24, undermines confidence in the outcomesrecorded in studies assessed using either dry combing or conditioned combing. Also it is arguedthat BBWC is necessarily at least as effective as WCWC because it involves washing with shampooand rinsing prior to application of conditioner, and CC “is unlikely to be as sensitive as either WCWCor BBWC, first because less immobilising moisture may reach the lice at the roots of the hair, theirmain habitat; second there is no failsafe second combing in the rinsed hair” (Ibarra, 2010) 28.

Basic importance of adopting the most reliable method of head louse detectionIn France, Combescot­Lang et al (2015) 29 tested the effectiveness of 21 formulated products,many available globally. They were used according to the packet instructions on head lice andtheir eggs collected from the heads of children and swiftly brought to the laboratory. Head liceremoved from their natural habitat are rapidly weakened by dehydration. Nonetheless, only 6products were rated potentially 100% effective. Moreover, the study authors insist that “clinicalefficacy can only be fully ascertained in a randomized controlled clinical trial”. We are of theopinion that in new field trials the most sensitive assessment method available, i.e. WCWC orBBWC, should be employed to measure outcomes.

In the public health interest, the provision of accurate knowledge to the carers – parents andhealth providers – should be paramount. Any “wet combing” education must take into accountthe busy world of parents, where time­effective + cost­effective + stigma preventive = efficacy inthe treatment of head lice. Promotion of a method which misses some of the lice is neithertime­effective nor cost­effective. Stigma prevention flows from a sense of empowerment overhead lice. This overcomes victimisation not only by lice, but society’s attitude to lice. It issourced from information on the life­cycle and behaviour of head lice, on the most reliable andpractical way to detect lice, on having the right tools to hand, and on participating in co­ordinated community detection on a pre­determined date and then checking the outcome ofany treatment choice (Olsen, 200230; Vander Stichele et al, 200231; Ibarra et al, 200718).

ConclusionThere is no such thing as generic wet combing and authors should explain the type andrationale for using it. The evidence in favour of identification of BBWC as the most sensitivemethod is incomplete. The findings of action research should be independently verified in full­scale field trials, including direct comparisons of CC with BBWC, and the PDC comb comparedwith the BB98 comb. These are basic issues in the eradication of pediculosis capitis, resolutionof which enables the competent authorities to introduce and maintain evidence­based,practical regulation of products to control head lice.

Competing interestsJI and CW are volunteer officers of Community Hygiene Concern, the not­for­profit UK charity whichdeveloped the Bug Buster comb (1988­1998) and conducts the BBWC programme.

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