Dandruff is flaking and itching of the scalp caused by low-grade inflammation. It is the mildest form of seborrheic dermatitis. It is not caused by a dirty or a dry scalp, and it settles quickly with the right shampoo used the right way. Head lice are small insects that live on the scalp and glue their eggs to the hair. They spread through head-to-head contact, they do not carry disease, and they have nothing to do with how clean anyone is. Treatment clears them, but it almost always has to be repeated.
The same eight facts on every condition comparison.
It is excessive scalp flaking.
Dandruff can come with itch.
It sits within seborrheic dermatitis.
It is often seen as a mild, scalp-only form.
Several factors contribute.
Malassezia, barrier changes, sebum and susceptibility all play a part.
Medicine must reach the scalp.
Treatment works on the scalp, not the hair lengths.
Lice live on the scalp.
They feed on the scalp and attach eggs to hair shafts.
Itching can come late.
It is a reaction to bites and may not start straight away.
Inspection comes first.
A fine-toothed comb in good light confirms lice before treatment.
Empty cases are not failure.
Hatched egg cases stay attached as hair grows.
White flakes Loose flakes on the scalp.
Flakes on clothing Visible on dark shoulders.
Itchy scalp Mild itch, no rash.
Adult lice Tan to gray insects about 2–3 mm long.
Nits on the hair Oval eggs glued close to the scalp.
Scratch marks Red bumps behind the ears and on the neck.
Dandruff involves uneven shedding of the scalp's outer skin cells. The interaction between scalp oils, Malassezia yeast and individual skin sensitivity contributes to visible flakes, usually with little obvious inflammation.
Head lice live among scalp hairs, feed on blood and attach their eggs to hair shafts. The body's reaction to their saliva causes itching, which may take time to develop after a first infestation.
Dandruff. Usually begins after puberty and may come and go through adult life.
Head Lice. Most common in school-age children; close contacts of any age can be affected.
Dandruff is flaking caused by an overgrowth of Malassezia, a yeast that lives on everyone's scalp, and the scalp's reaction to it.
Head lice are tiny insects that live only on the human scalp. They can't jump or fly, so they spread by crawling from one head to another.
Evidence labels come from each condition’s own treatment list.
The workhorse dandruff shampoo: it reduces the yeast and calms the scalp, and it is gentle enough to keep using for years. Part the hair, work it into the skin rather than the lengths, and leave it on for five minutes. It is a good choice for color-treated, gray or relaxed hair because it does not discolor.
Reduces the yeast and also slows how fast scalp cells shed, which makes it useful when the flaking is heavy. Rinse it thoroughly. The catch is color: it can discolor light, gray, relaxed or color-treated hair, so zinc pyrithione or ketoconazole is usually the better pick for those.
Works by slowing the shedding rather than by treating the yeast, so it suits thick, heavy flaking more than a mildly itchy scalp. It smells strongly and it stains light hair and fabric, which is why most people use it only during a flare. It is also useful when scalp psoriasis is in the picture too.
This one lifts scale rather than treating the cause. It is the right choice when the scale is thick and stuck down and other shampoos cannot reach the skin underneath. Use it first to clear the way, then follow with an anti-yeast shampoo — on its own it will not stop the dandruff coming back.
A 5 percent tea tree shampoo did beat a plain shampoo in one small trial, so it is not nothing. It is weaker than the standard actives and there is much less behind it. It is also a common cause of allergic contact dermatitis, so if the scalp becomes more itchy and irritated on it, that is a reason to stop rather than to persist.
Sold in several natural lice products and not shown to clear an infestation reliably. It irritates the scalp of a child who is already scratching, and it is a common cause of allergic reactions. If the older products have stopped working, a prescription treatment is a better answer than an essential oil.
The usual first treatment, applied to dry hair, left the stated time and rinsed, then repeated in seven to ten days because it does not reliably kill eggs. Where lice are not resistant it works well. Resistance to it is now common in many areas, so if two proper courses fail, the answer is a different medicine, not a third round.
The other older over-the-counter option, from chrysanthemum extract, used the same way with a repeat in seven to ten days. It kills fewer eggs than permethrin does and lice are commonly resistant to it. It is avoided in anyone with a ragweed or chrysanthemum allergy.
A silicone lotion that coats and suffocates the lice rather than poisoning them, so resistance is not an issue with it. It is left on for the stated time — often several hours or overnight — and repeated a week later. It is a good option for a child who has already failed permethrin, and it is gentle on the scalp.
Ketoconazole 2% shampoo. Double the strength of the version on the shelf, and the usual first prescription when a month of over-the-counter shampoo has not shifted it. Twice a week for a month, five minutes on the scalp each time. Once it is clear, most people drop back to an over-the-counter shampoo for maintenance rather than staying on this.
Ciclopirox shampoo. A different antifungal, and the usual next step when ketoconazole has stopped working or was never tolerated. It is used two or three times a week in the same way, with contact time on the scalp. Rotating it with a zinc pyrithione shampoo is a common way to keep a stubborn scalp under control.
Clobetasol Propionate. A potent steroid, prescribed for the scalp as a solution, foam or shampoo, that settles a red, sore, intensely itchy flare within days. It is for short bursts of two to four weeks, not for keeping on hand. It does nothing about the yeast, so the medicated shampoo carries on alongside it and takes over afterwards.
A newer non-steroid foam approved for seborrheic dermatitis, used once a day on the scalp and face. It calms the inflammation without the thinning that comes with long-term steroid use, which makes it a reasonable option for people who keep needing steroid courses. Cost and insurance are usually the limiting factor.
A non-steroid ointment used mainly where dandruff has spread onto the face — the eyebrows, the creases beside the nose, behind the ears. It calms the same inflammation without thinning that thin skin, which matters when the area needs treating on and off for years. It stings for the first few days. It is awkward to apply in hair, so it is rarely the choice for the scalp itself.
Ivermectin lotion 0.5%. A single ten-minute application to dry hair, and usually no repeat is needed, because it kills the young lice as they hatch. That makes it a good choice for families who have already skipped or fumbled a second application. It is one of the main options when permethrin has failed.
Spinosad suspension. A ten-minute application to dry hair that kills both lice and most eggs, so a second treatment is often unnecessary. High cure rates in studies against permethrin-resistant lice. Cost and availability are the usual limits rather than how well it works.
Malathion lotion. An older prescription lotion that kills lice and many eggs, applied to dry hair and left on for the stated time. It works where permethrin has failed. It smells strongly, it is flammable while wet so no hairdryers, flames or cigarettes near it, and it is not used in young children.
Benzyl alcohol lotion. It works by blocking the breathing holes of the lice rather than poisoning them, so resistance is not expected. It does not kill eggs, so the repeat in seven days is essential. It can sting and irritate the scalp, which matters if the skin is already scratched.
An antifungal tablet, occasionally used for a short course when seborrheic dermatitis is severe, widespread, or not responding to anything applied to the skin. Ordinary dandruff never needs it. It also does not keep it away — shampoo maintenance still has to carry on afterwards — and it interacts with a number of common medicines.
Ivermectin tablets. A tablet taken as two doses about a week apart, used when repeated topical treatments have failed or when applying a lotion to the whole scalp is not practical. It is effective in that situation. It is not used in small children or in pregnancy, so the prescriber checks weight and circumstances first.
Dandruff comes in waves - quiet stretches broken by flares. It can carry on for decades without getting steadily worse, and it follows a rough arc through life.
Left alone, head lice do not clear. They cause no lasting damage; the problems come from scratching, and occasionally infection on top.
Dandruff is a mild scalp form of seborrhoeic dermatitis. Itching and flaking can recur; marked inflammation or persistent symptoms may indicate a condition needing a different treatment.
Infected scalp and neck
Scratching breaks the skin, and bacteria can get in on top. The signs are redness and swelling that spreads, weeping or honey-colored crusts at the nape and behind the ears, and tender glands in the neck. It is the main reason a case of lice ever needs antibiotics, and it needs to be seen. Treating the lice properly and settling the itch early is what prevents it.
Weeks of broken sleep and worry
The lasting harm from head lice is rarely medical. It is the itching that keeps a child awake, weeks of repeat treatments and combing, missed school where old exclusion policies are still used, and the embarrassment that makes families treat it in secret. Telling the school and the other families is the single most effective thing for ending the cycle, and it is the step people most want to skip.
Seek assessment for persistent symptoms despite dandruff shampoo, marked redness, pain, crusting or patchy hair loss.
Ask a pharmacist or clinician if you cannot confirm live lice, treatment fails, or scratching causes sores or infection.
Usually not. It is commonest on oily scalps, and the yeast behind it feeds on that oil. The scalp can feel dry and tight because it is inflamed and the barrier is disrupted, which is not the same as being short of moisture. Treating it as dryness makes it worse.
More often than you otherwise would, at least during a flare, because washing removes the oil the yeast lives on. If frequent washing damages your hair, change how you wash rather than how often - medicated shampoo straight onto the scalp, five minutes, condition only the lengths.
Not permanently. A very itchy, inflamed scalp that gets scratched or picked sheds more hair for a while, and that recovers once the inflammation settles. Thinning or bald patches need their own assessment, not a stronger shampoo.
Usually one of two things. Either contact time slipped and it is being rinsed straight out again, or the scalp has stopped responding to that active. Rotating two medicated shampoos, such as zinc pyrithione and ketoconazole, tends to keep working.
Yes - the same condition in a different place. Seborrheic dermatitis affects the oily areas of the body, and the scalp is the most obvious one. The face usually responds to a gentle antifungal cream or a short course of a mild anti-inflammatory prescribed for that area, not to shampoo left on the skin.
Generally yes, but the active matters. Selenium sulfide and coal tar can discolor light, gray, relaxed or color-treated hair. Zinc pyrithione and ketoconazole are the usual choices, and conditioning the lengths limits drying of the hair shaft.
Almost certainly direct head-to-head contact with another child — playing on the floor, a sleepover, photographs head to head. Not the house, the pets or anyone's hair. By the time you find them the contact was weeks ago.
Major pediatric and public health bodies advise against sending children home for lice. By the time they are found they have usually been there for weeks, and lice do not spread easily in a classroom. Tell the school, start treatment, and in most places the child stays. Check your school's policy — some are stricter than the guidance.
No. It makes future checks easier and reassures everyone, but empty shells are harmless and grow out. What matters is that no live lice remain. Combing with conditioner and a metal comb beats picking them out dry.
Because the itch is an allergic reaction, not the lice, and takes one to two weeks to settle after the last louse is gone. The scalp has also been scratched and treated with something drying. Itching alone is not a reason to treat again. Finding a live louse is.
Check everyone the same day and treat the ones with live lice. Some doctors also treat anyone who shares a bed, even with no live lice found, because that contact is so close. Treating the whole household regardless is not recommended.
In order of likelihood: the second application was skipped, the product was misused, someone else in the house was not treated, reinfection came from the same friend or classroom, or the lice are resistant. Only the last is a reason to change medicine, so work through the other four first.
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