How to distinguish bed lice from head lice? - briefly
Bed lice (Cimex lectularius) are 5–7 mm, reddish‑brown insects that inhabit mattress seams and bite exposed skin, while head lice (Pediculus humanus capitis) are 2–4 mm, grayish and cling to hair shafts on the scalp. The former is transmitted via infested bedding, the latter spreads through direct head‑to‑head contact.
How to distinguish bed lice from head lice? - in detail
Body lice (Pediculus humanus corporis) and head lice (Pediculus humanus capitis) are distinct ectoparasites that require separate identification strategies. Both species are small, wing‑less insects, but they differ in morphology, habitat, feeding behavior, and signs on the host.
Morphological differences are observable under magnification. Body lice are slightly larger, measuring 2–4 mm, with a broader abdomen and a more robust thorax. Their legs are shorter, and the hind legs lack the claw‑like hooks seen in head lice. Head lice are 2–3 mm long, possess a narrower abdomen, and have longer legs equipped with clawed tarsi that facilitate grasping hair shafts.
Habitat and transmission provide clear clues. Body lice reside on clothing seams and lay eggs (nits) on fabric, moving to the skin only to feed. Infestations are common in situations with poor hygiene and infrequent laundering. Head lice live directly on the scalp, attaching their nits to hair strands within 1 mm of the scalp surface. Transmission occurs through direct head‑to‑head contact or sharing personal items such as combs or hats.
Clinical signs differ in location and appearance. Body lice produce intense itching on the trunk, especially around the waist, hips, and underarms, where they bite. Their bites appear as small, red papules that may become infected. Head lice cause itching on the scalp, neck, and behind the ears. Nits are firmly attached to hair shafts and are difficult to remove; they appear as oval, white or yellowish shells that can be seen close to the scalp.
Diagnostic steps:
- Collect a specimen using a fine‑toothed comb or tweezers.
- Examine under a light microscope or magnifying glass.
- Identify the nits: body‑lice nits are larger, have a more elongated shape, and are often found on clothing fibers; head‑lice nits are smaller, oval, and attached to hair.
- Observe the adult insect: body lice lack claws on the hind legs, while head lice possess them.
- Note the infestation site: clothing versus scalp.
Treatment protocols also diverge. Body‑lice infestations respond to thorough laundering of clothing and bedding at temperatures above 60 °C, combined with topical insecticides if needed. Head‑lice infestations require direct application of pediculicidal shampoos or creams to the hair and scalp, followed by nit removal with a fine comb.
Understanding these distinctions enables accurate diagnosis, appropriate intervention, and prevention of re‑infestation.