Lice vs. Dandruff: What Is the Difference?

An itchy scalp, coupled with the visual presence of tiny spots in the hair, usually leads people to think of one of two common issues – dandruff or head lice.

While the two skin conditions share some commonalities in how they feel, the similarities start and end there. In fact, dandruff and head lice are quite different. Understanding the differences between them is important for effective identification and treatment. This blog will identify how to distinguish dandruff from head lice and what sets them apart from each other.

What is dandruff?

Dandruff is a specific type of seborrheic dermatitis that occurs on the scalp. Seborrheic dermatitis is a chronic type of eczema (atopic dermatitis) that causes red, itchy skin. This type of dermatitis can occur anywhere on the body, but it’s called dandruff when it appears on the head.

The exact trigger is usually tied to excess skin oil or a reaction to a type of yeast that lives on the skin. Whenever there is too much oil on the scalp and hair follicles, skin cells can build up and die. The dead cells then shed or flake off, leaving specs of skin throughout the hair. Excess Malassezia yeast on the scalp can also trigger a reaction, which causes skin irritation and flaking.

Dandruff is common in both children (called cradle cap when it affects infants) and adults. People born with oily skin are more prone to developing dandruff. Environmental triggers, such as stress, cold or dry weather, harsh soaps or shampoos and hormonal changes, can all lead to dandruff.

What is lice?

Head lice, also called Pediculus humanus capitis, are tiny insects that can invade anyone’s scalp and survive in the hair for weeks. Head lice is a common occurrence among school-aged children, and affects 6 to 12 million people each year.

Head lice can be spread from person to person by crawling (they can’t fly or jump). Once on the scalp, they feed on the blood supply and lay eggs. These eggs are clear or white and can easily be mistaken for dandruff to the naked eye. Despite the association of head lice and poor hygiene, the insects actually prefer clean hair to invade.

There are three stages of head lice:

Eggs: Also called nits, the eggs are attached to hair near the scalp and take 7 to 12 days to hatch.

Nymphs: Once the egg hatches, it becomes a smaller version of adult lice called nymphs (about the size of a pinhead). It takes 9 to 12 days for a nymph to become an adult.

Adults: Mature head lice are about the size of a sesame or strawberry seed. Unlike the white eggs, adult lice are yellow or gray and move fast. They can live for three to four weeks and have the ability to lay 10 eggs per day. Only adult lice can pass from person to person.

The main differences between lice and dandruff

There are several distinguishing factors between head lice and dandruff, ranging from the cause and symptoms to the location on the scalp and how to treat them.

Causes

In the most simplistic terms, head lice occurs from a parasitic insect, whereas dandruff is a skin condition.

Head lice: Head lice are tiny, crawling insects that spread through direct head-to-head contact. While less common, head lice can also spread through shared items – hats, combs, brushes, sheets, towels, pillows, headbands or bows.

Dandruff: Dandruff is a mild form of seborrheic dermatitis that causes excess skin cells to shed or flake off. The scalp has oil glands (sebaceous glands) that protect the skin from drying out. In some people, too much oil is present and it causes a build up of skin cells that eventually flake off. Excess yeast on the scalp can also trigger a reaction that causes dry, itchy skin.

What to look for

Dandruff and lice may look the same from afar, but up close they’re vastly different. Plus, one moves easily while the other tends to stick to hair.

Head lice: When combing through the hair or examining with a magnifying glass, you may visibly see eggs or adult lice. Eggs are usually yellow or white and appear close to the scalp. Adult lice are gray or pale. Adult lice move quickly and are hard to spot, especially in light. The easiest way to distinguish head lice and dandruff is how easy the specs move. The eggs secrete a glue-like substance that allows them to stick to hair.

Dandruff: Dandruff is a piece of dry, flakey skin. The scales usually have a white-to-yellowish color. Unlike head lice, dandruff moves freely whenever you run your hands through your hair or shake your head. Since it moves so easily, dandruff may fall off and appear on your shoulders, back, chest, clothes, bedding or towels.

Location

In general, head lice are found in close proximity to the scalp.

Head lice: Adult lice lay eggs within a few millimeters of the scalp so the eggs can survive – they need warmth from the scalp and a blood supply to grow and develop. Finding a white or yellow spec near the scalp would indicate a lice infestation.

Dandruff: Dandruff can appear anywhere on the head or hair. The farther away you find a spec, the more likely it’s dandruff (although a dead egg could appear away from the scalp).

Symptoms

Head lice and dandruff both cause an itchy scalp, but there are other specific symptoms to each issue.

Head lice: Adult lice move frequently at night, so it may feel like something is moving in your (some people note a tickling sensation). Droppings and saliva from the lice can cause itching. Red bumps or sores may also appear.

Dandruff: Aside from flakey skin, dandruff can also cause a dry or greasy rash on the scalp. The rash is usually red in people with light skin, while it may appear a purple or pink color in people with darker skin. Raw or crusty areas of skin may also be noticeable.

Transmission

Head lice: Head lice can spread to another person through direct head contact, which explains why it’s so common in schools. 

Dandruff: Dandruff isn’t contagious and can’t be transmitted from person to person.

Treatment

Over-the-counter shampoos and creams are both used to treat head lice and dandruff, but the active ingredients differ.

Head lice: Treatment usually involves two steps – killing adult lice with a shampoo, cream or lotion and removing eggs with a fine comb (not all products kill eggs). Several treatments are needed to kill the lice, a process that can take up to three weeks. Examples of treatments include permethrin lotion, pyrethrin shampoo, ivermectin lotion, malathion lotion and spinosad topical suspension. These medications are insecticides approved by the FDA to treat infections caused by parasites. Malathion and spinosad both require a prescription. If you don’t want to use any chemicals in you or your child’s hair, you’ll need to comb the hair several times a week for at least three weeks to remove the lice.

Dandruff: There isn’t a cure for dandruff since it’s a lifelong condition. Instead, treatment can prevent or address flare ups. Dandruff shampoos that contain zinc pyrithione, ketoconazole or selenium sulfide serve as the most common treatment. If over-the-counter shampoos don’t work, a doctor can prescribe antifungal shampoos that contain ciclopirox or ketoconazole. Other products may contain steroids such as clobetasol, fluocinolone or betamethasone valerate to reduce redness and itchiness.

While many over-the-counter shampoos, lotions and creams can help get rid of dandruff or lice, you should schedule an appointment with a dermatologist if symptoms persist.  For more health and wellness tips, visit the INTEGRIS Health For You blog.