Head Scratching Could Mean Lice

By Chris Williams on January 26, 2012.

Winter is here and so are the head lice.   Estimates based on the sale of lice control products show that millions of cases occur yearly.  Of the three types of lice that infest humans, head lice are by far the most common, followed by pubic lice, and lastly body lice.   Head lice are most common among school age children, and readily spread through close contact.  Sleepovers, hat sharing, and close play allow lice to move from head to head.   Pubic lice, usually associated with sexual contact, prefer the groin and armpit area.  Pubic lice are not as easily transferred as head lice.  Body lice, the least common lice, are associated with indigent adults who sleep in their clothes and bathe infrequently.  Head  and pubic lice lay their eggs on the hair shaft of the host while body lice deposit eggs in the hosts clothing.  Throughout history  body lice have been linked to typhus, trench fever, and endemic relapsing fever.  The good news, if there is any, is that head lice have not been shown to transmit typhus and relapsing fever, although currently work is being done concerning the spread of more recently occurring transmissible diseased carried in the blood stream.

Head lice are small wingless insects roughly 1.5mm-3mm in length.  Tiny sucking mouth parts allow nymphs and adults to feed on human blood.  They have six legs, each with a terminal, hook like claw.  The claw is adapted for holding the hair shafts and allows them a firm grip and the ability to move fairly quickly through hair.  With bodies a white, tan to grey color, the adults are visible to the  naked eye when viewed in bright light.  Female head lice lay one egg per hair shaft, attached with a strong secretion that anchors the egg in place.  Daily, females may produce 4-8 eggs, and may lay an estimated 50 to 300 eggs during her life.  Eggs, 90% of which hatch in 6-12 days, give rise to nymphs who can mate and reproduce in 10 days.  With a life cycle of about 15 days, and a life span of about 24 days total, head louse populations can quickly get out of hand.

head-liceBecause head lice only feed on human blood(their sucking mouth parts evolved to feed through human skin),  they cannot survive off of the host for long.  Studies show that the time an adult louse can survive is temperature dependant.  The warmer the temperature, the shorter the time off the host seems to be the trend.  At 73 degrees F., adults live up to 55 hours, and at 55 degrees F. they lived 10 days.  Eggs were the most resistant to being off the host but did not survive one month at room temperature, and higher temperatures killed adults and eggs quite quickly.  The eggs, or nits may sometimes be found on hair in hats, combs, brushes, bedding, towels, and upholstered furniture.

Signs that your child, or you may have head lice include constant head scratching, scalp damage due to irritation from scratching, and/or red to blackish fecal pellets on shoulders and back.  Head louse bites are painless but the saliva associated with the bite will produce an allergic reaction that itches.  Scratching may cause damage to the scalp, allowing germs, feces, and damaged lice to be introduced into wounds causing secondary infection.  Impetigo, swollen glands, along with fever, irritability, and tiredness may by symptoms of a severe infestation.  Nymphs and adult lice may be present actively moving about the head and eyebrows.  Nits, or eggs may be visible on the hair  shafts, glued close to the scalp.  Nits may also be found on hairs around the ears and nape of the neck.   Most school nurses have tools such as lice sticks for parting hairs, nit combs for finding eggs, and lights with special bulbs and magnifying lenses for inspection of the head area.

Control of head lice can be difficult but is possible.  Head lice can be controlled without the use of toxic pesticides.   Combing with metal nit combs, shampooing in hot water, using soaps, and as a last resort, the use of least toxic pyrethrin based insecticidal shampoo.  Lice have become resistant to some of the more common over the  counter lice control products, some of which are quite toxic, especially where very young children are concerned and are not necessary to control head lice.  Common soaps that contain long chain fatty acids(made with or based on olive or coconut oil), although non-pesticidal, kill nymphs and adults.  Oil based shampoos may be purchased where hair products are sold.  Hair dryers will also kill some of the nymphs and adults as well as some of the eggs.  Directly after shampooing, the hair is moist and easily combed through.  Using a bright light will aid in spotting the adults and nits, and a bowl of hot water should be used to clean  the nit comb after every pass to kill and remove lice and eggs.  A schedule that combines hot shampoo with soap and combing out lice/nits every week for at least three weeks should work.    Hats, combs, brushes, scarves, pillow cases, bedding, and towels should be cleaned or laundered to kill any adults or eggs that might have left or fallen off the host.  30 minutes in the dryer will kill all stages of head lice, and the eggs.  This should take place at the time of initial treatment.

Insecticides should only be used as tool of last resort, Pyrethrin based or synthetic pyrethroid(Permethrin)  insecticides are less toxic to humans than preparations containing Lindane(a very dangerous chemical compound).  Studies how that lice are already resistant to Lindane.  Always follow label instructions when using any pesticide, and store them out of reach of children.



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