Race. All hair is not alike. The hair of Caucasians, Orientals, and native Americans is round in cross section, whereas those of African descent have hair that is oval in cross-section. The lice that predominate in the U.S. are thought to have arrived with the early Caucasian settlers. Having evolved with their hosts, they are only able to grasp the rounded hair with their claws(1). They cannot easily grip the oval hair shaft. For this reason, Black children are rarely infested in the U.S., although every other group is at high risk. Conversely, African lice are evolved to grip the oval hair, so those with rounded hair shafts are largely protected from infestation with the native lice found in Africa, and African natives are at high risk in their home country.

CONFIRMATION OF HEAD LOUSE INFESTATION
When a patient suspects head lice, what can the pharmacist do to help confirm their presence? The most obvious thing is to inspect the heads. The technique of checking heads is not difficult, once the pharmacist is properly trained. I use it in my practice and also in the mass screening programs which I have conducted.

Confirmation via Combing. I have heard students and other professionals speak about seeing heads that are so heavily infested that the hair is literally crawling with lice, even to the extent that the hair seems to move. However, these patients are the exception. Rather, the pharmacist or other examiner must conduct a painstaking search to confirm an infestation.

The pharmacist should expect to find few live lice during an exam, perhaps no more than 5-10. United States lice are tan in color, matching the background Caucasian skin (lice found in Africa are darker, matching the predominant skin color of its native residents). American lice can be compared to a sesame seed in size and color, except your typical sesame seed is not capable of locomotion. Head lice have receptors on their body which sense movement of adjacent hairs. When the pharmacist parts the hair, they scramble to safety in the nearest dense bundle of hair, making them hard to see and even more difficult to capture.

When checking the head, there are several specific steps that should be followed:

• Wear disposable gloves;
• Find a location with good light, preferably direct sunlight. This may require seating both the patient and examiner outdoors on a patio or the pharmacy's back porch. If this is not available, a strong lamp may be sufficient;
• If the examiner is far-sighted, has poor vision or any other visual detail abnormality (e.g., amblyopia), a magnifying glass may be necessary;
• Remove tangles from the hair with a comb or hairbrush;
• Divide the hair into sections, examining each section individually and fastening it away from non-examined hair when it is inspected;
• Grasp a one-inch section of hair and use a lice comb to comb each hair section carefully and slowly from the scalp outward to the end of the hair. Lice combs traditionally sold for lice detection/removal are made of a one-piece plastic or metal construction that hinders their efficiency greatly. However, a recently introduced lice comb is rapidly becoming the standard for lice detection and removal. Known as the LiceMeister ^�, it is made by embedding 32 stainless steel teeth in a rigid plastic handle. The teeth are long and tapered, and are set so close that combing removes virtually all lice, both adults and nymphs, and virtually all nits. Thus, this innovative device can both screen for the presence of lice and remove them to halt an infestation(5).
• Dip the LiceMeister^� into a cup of water after each hair section is combed. If debris (e.g., nits, builds up between the teeth of the comb, use a toothbrush or dental floss to clean between them.
• Continue combing each section of hair until all is thoroughly combed.
• If the exam is negative, caution the parent or caregiver to screen each day, as long as lice infestation is still possible or suspected.

Simple Visual Confirmation. If the LiceMeister is not available, the pharmacist may still be able to detect head louse infestation, although it is more difficult to inspect all of the hair. In this case, the pharmacist should still use gloves, strong light and a magnifying glass if necessary. The hair may be parted with wooden paddles and inspected carefully. The efficiency of this method is far lower than with combing.

When simple visual confirmation is sought, the pharmacist should look for live lice, but also the oval-shaped nits attached to the hair shaft. It is almost impossible to tell visually which nits are still incubating eggs and which are hatched, but there are several clues. Nits most likely to be viable are those closest to the scalp. Hair grows about 0.35 mm daily, so a nit which is located as far as 1 inch from the scalp was probably laid as long as 2.6 more months ago. If this nit is not empty, it is not viable in most cases, since its probable residence time on the head exceeds the incubation period. As lice themselves depend on frequent blood meals, they are most often found next to the scalp, and this is where laid eggs have the best chance of hatching since it is in closest proximity to human body heat. However, there are exceptions. In some way, a gravid female louse's behavior changes when she is in a warm climate, where the ambient air is close to human body heat, or exceeds it. In these cases, she may lay an egg anywhere along the human hair shaft, since outside temperatures facilitate hatching. So it is not enough to examine distance from the hair to determine viability of a nit. One must also take the temperature of the ambient air into account. On a cold Minnesota day, a nit located two inches from the scalp would probably not be viable, but on a warm Texas summer day, it might well be viable.

The appearance of the nit is also a clue to its viability. A nit which still contains a viable or dead unhatched louse appears darker and translucent, whereas an empty egg case appears whiter, more dull, and more opaque. Since these judgments are difficult at best with the naked eye, I confirm them with a microscope when feasible. I ask the patient if I may examine strands of hair with nits in situ and remove several for later inspection, also taking a home or work phone number from the patient. After a microscopic examination, I can call the patient to provide instructions the following day. This final step continues the requirements for providing pharmaceutical care for head lice, by helping ensure that the patient is properly treated.

Differentiate Pseudonits. When looking for nits, the pharmacist must be alert to pseudonits which resemble nits but which are not signs of louse infestation. A pseudonit is any object found in the hair which can cause diagnostic confusion. This wide range of residue can include dandruff scales, dirt or small plant matter blown into the hair, or flakes from hair spray or hair grooming aids. Generally, if the matter can be easily flicked from the hair with the finger, it is not a nit, since the glue used by the mother louse to cement nits holds them tightly. An exception is an object known as the desquamated epithelial cell plug, which is ejected from a hair under certain conditions. It encircles the hair, and cannot be easily removed. Again, a microscope will differentiate these nonviable objects from nits.

Look for Lice Feces. Lice feces are dark in color. They may fall into the inner collar of a shirt or blouse, where they become lodged in the clothing. As the person turns the head from side-to-side, body moisture spreads the feces along the inner collar. The pharmacist may note these black streaks as an indicator of louse infestation.