What is seborrhoeic dermatitis, and is it the same as dandruff?
Close to it: they are two ends of one spectrum. A 2015 review describes dandruff as itchy flaking of the scalp without visible inflammation, and seborrhoeic dermatitis as flaking with inflammation and itch that can also affect other oil-rich areas. DermNet describes dandruff as the uninflamed form. Together they are estimated to affect half of adults, and the same review says it starts at puberty and peaks in early adult life.
In one study quoted by that review, dandruff was found in 30 to 42 per cent of Chinese people compared with 66 to 82 per cent of Caucasians. That is a figure from one US and China study, not a Malaysian one, and it shows how widely rates differ between groups. It is a benign condition, but it is visible, itchy and often embarrassing.
What causes it?
Three things meet on oil-rich skin. Malassezia are yeasts that live on most people's skin and feed on its oil. Their enzymes split the oil into fatty acids, including oleic and arachidonic acid, and the 2015 review reports that these disturb the skin barrier and trigger inflammation, with or without visible redness. And a person's own susceptibility decides how strongly the skin reacts: the same review notes it is commoner with immune suppression, including HIV, and with Parkinson's disease.
One clue to the mechanism is that every effective agent in the review shares an antifungal action, whatever its chemical class. The review and DermNet list poor sleep and stressful events as aggravating factors, and DermNet notes winter flares that improve in summer. That seasonal pattern comes from cooler climates, and the sources give no figure for humid ones, so flares in Malaysia cannot be predicted from the calendar.
Where does it show on the scalp, face and body?
The scalp, then the face and upper trunk. DermNet lists the scalp, nasolabial folds (the lines from nose to mouth corner), the glabella (between the brows), the eyebrows, the beard, the ears, the skin behind the ears and the sternum. The 2015 review cites the face in 87.7 per cent of adult cases, the scalp in 70.3 per cent and the upper trunk in 26.8 per cent.
The scale can be white to yellowish and oily or dry. Itch is common on the scalp but not obligatory. The usual complication is secondary bacterial infection, which increases the redness and weeping. When the eyelid margins are scaly and red, the same process can sit there too, as DermNet notes under blepharitis.
How is it different from psoriasis, rosacea and eczema?
By the thickness of the scale, the pattern on the face and the sites. Psoriasis plaques are thicker and sharply limited with silvery white scale, while seborrhoeic scale is ill-defined. Rosacea tends to sit on the cheeks, spares the nasolabial folds, has no scale and comes with flushing or visible small vessels, whereas seborrhoeic dermatitis is scaly in the nasolabial folds, eyelids and eyebrows without flushing. The 2015 review also lists tinea capitis, a scalp ringworm that gives scaly patches of hair loss with black dots at broken hairs.
Seborrhoeic dermatitis is itself a form of eczema or dermatitis, according to DermNet, and the 2015 review notes it rarely affects the extensor surfaces such as the outer elbows and knees. It can also coexist with psoriasis, and a mixed picture is called sebopsoriasis. A related yeast problem appears on the trunk as patches of panau (tinea versicolor), and Malassezia can inflame hair follicles too, which is covered in the article on cystic, hormonal and fungal acne. A doctor tells these apart by looking, and rarely needs a biopsy.
How is it treated?
With medicated shampoo or cream for the yeast, and a short course of anti-inflammatory cream for a flare. A 2015 Cochrane review of 51 trials (9,052 people) found ketoconazole 2% cut the risk of failed clearance by 31 per cent against placebo at four weeks (low-quality evidence), gave remission similar to steroids and caused 44 per cent fewer side effects. Ciclopirox 1% also beat placebo. A 2014 Cochrane review of 36 trials (2,706 people) found steroids cleared symptoms more often than placebo (relative risk 3.76) and matched azoles and calcineurin inhibitors in the short term, with fewer adverse events than calcineurin inhibitors.
The usual pattern is a loading phase, then maintenance. The 2015 review lists ketoconazole 2% twice a week for four weeks and then weekly, zinc pyrithione 1% two to three times a week, and selenium sulfide 2.5% (which can stain the scalp orange-brown) twice a week for two weeks and then weekly. DermNet describes shampoos twice weekly for at least a month and, if needed, indefinitely, and adds that some Malassezia strains resist azoles, in which case zinc pyrithione or selenium sulfide may be tried. For flares, DermNet describes a mild steroid for one to three weeks, with a calcineurin inhibitor (tacrolimus or pimecrolimus) when steroids would be needed often. The review lists skin thinning, visible small vessels and lighter patches as risks of prolonged steroid use, which is why prescription creams are used for short courses on a doctor's plan.
The evidence has limits. Most trials lasted four weeks or less, 24 of the antifungal trials had a conflict of interest, and there is no evidence on long-term or intermittent steroid use. A 2024 expert consensus of dermatologists notes that approved therapies for moderate and severe scalp disease do not exist, and proposes an algorithm by severity.
Does it cause hair loss?
Not directly. The 2015 review states that seborrhoeic dermatitis is not associated with hair loss, and uses that point to tell it from tinea capitis. A 2026 review calls alopecia not a typical feature, but adds that chronic inflammation may be linked to shedding (telogen effluvium), and that heavy scaling and scratching may contribute indirectly. It also reports that seborrhoeic dermatitis is present in 40 to 50 per cent of people with androgenetic alopecia (pattern hair loss), and says that coexistence does not necessarily prove one causes the other.
So thinning hair in someone with dandruff needs its own assessment, because treating the flakes does not treat pattern loss. The hair thinning page explains how a cause is found, hair loss in Malaysia: which doctor to see covers who to see, and minoxidil and finasteride covers the medicines for pattern loss.
When should you see a doctor?
When it does not settle, when the diagnosis is uncertain, or when something else is going on. That means no clear improvement after about a month of correct shampoo use, skin that is painful, weeping or crusted (the review names secondary bacterial infection as the main complication), patches of hair loss with scale, thick plaques, a sudden widespread rash, or flaking that comes with other new symptoms. The review adds that seborrhoeic dermatitis is often more extensive and harder to treat when the immune system is suppressed. A doctor can confirm the diagnosis, check for look-alikes and set the plan.
Scaly, red eyelid margins are a separate question because the eye is involved. Dr Catherine Chow, an oculoplastic surgeon, explains the seborrhoeic type of eyelid margin disease in her article on blepharitis and crusty, sore eyelids. Flaking on a baby or child should be seen by a child's doctor.
So what is the honest answer?
Dandruff and flaky red skin on the face are usually one chronic, relapsing condition that responds to antifungal shampoo and short courses of prescription cream, and that returns when treatment stops. Hair loss is a separate problem to assess on its own. The most useful first step is a diagnosis, because psoriasis, rosacea, ringworm and eczema are treated differently.
